Temperature correction of depth values in three-dimensional data of a dental object

Abstract

The present disclosure relates to a computer-implemented method and an intraoral scanning system. The intraoral scanning system is configured to determine temperature corrected depth values in three-dimensional data of a dental object. The intraoral scanning system may include an intraoral scanner configured to acquire, by a first image sensor, three-dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner, a memory unit that includes a first calibration data set measured at a first inner temperature of the intraoral scanner, and a second calibration data set measured at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature. The system may further include one or more processing units configured to determine first calibration depth values by correlating the acquired three-dimensional data to the first calibration data set, determine second calibration depth values by correlating the three-dimensional data the second calibration data set, and determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

Description

[0001] TEMPERATURE CORRECTION OF DEPTH VALUES IN THREE- DIMENSIONAL DATA OF A DENTAL OBJECT FIELD

[0002] The disclosure relates to a method and an intraoral scanning system that is configured to temperature correct depth values in three-dimensional data of a dental object. More specifically, the temperature correction involves calibrating the acquired three-dimensional data according to calibration data set provided at different temperatures.

[0003] BACKGROUND

[0004] The performance of an intraoral scanner may be sensitive to transient thermal effects. More specifically three-dimensional data accuracy may be affected due to the long time for the scanner to get to thermal equilibrium. An intraoral scanner may be calibrated, at a single temperature, for example at thermal equilibrium, at the production site as part of the fabrication process. Thermal expansion of mechanical parts within the scanner consequently causes the calibration not to be accurate if scanning commences before this thermal equilibrium is reached. In other words, the calibration is not completely correct unless the scanning is performed at the same temperature as the calibration was performed at. This may be an issue in the field where the user often turns on the scanner and immediately starts scanning.

[0005] One may go around the issue by pre-heat the scanner for a certain period of time before usage to ensure that the optical system has reached thermal equilibrium. This is however annoying to the user and significantly reduces the battery lifetime. Another way may be to use expensive material with low thermal expansion. This is however costly and significantly increases mechanical complexity. Yet another way could be to tailor the thermal expansion coefficients of different materials to counteract to result in net low thermal expansion, this will however also increase the mechanical complexity

[0006] significantly.SUMMARY

[0007] It is an aspect of the present disclosure to overcome the above-mentioned problem by not introducing any form of mechanical complexity to an intraoral scanner. The disclosure relates to an intraoral scanning system configured to determine temperature corrected depth values in three-dimensional data of a dental object. The system may include an intraoral scanner configured to acquire, by a first image sensor, three-dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner. In another example, the intraoral scanning system may include a plurality of image sensors that is configured to acquire three-dimensional data of the dental object. The temperature sensor may be arranged in vicinity to the first image sensor and / or a light source of the intraoral scanner. The intraoral scanner may include a plurality of temperature sensors configured to measure inner temperatures at different locations within the intraoral scanner.

[0008] The intraoral scanning system may include a memory unit that includes a first calibration data set that have been measured at a first temperature of intraoral scanner, and a second calibration data set measured at a second inner temperature of the intraoral scanner, wherein the second temperature is higher than the first temperature. The first and the second calibration data set may be measured by the manufacturer of the intraoral scanner and during the fabrication of the intraoral scanner. The calibration set may include pixel positions and corresponding depth configurations of the intraoral scanner, wherein the pixel positions and the corresponding depth configuration may be used for generating three-dimensional data. The content of the corresponding depth configurations may be depended on the type of intraoral scanner. The type of intraoral scanner may be a triangulation scanner or a focus scanner. For example, the intraoral scanner may be a focus scanner, and the depth configurations may include positions of a moving lens, and in another example, the intraoral scanner may be a triangulation scanner, and the depth configurations include pixel positions of corresponding pixels that includes same parts of the dental object. In one example, the first inner temperature may be around 35 degrees Celsius, and the second inner temperature may be around 60 degrees Celsius.The intraoral scanning system may include one or more processing units that may be configured to determine first calibration depth values by correlating the acquired three-dimensional data to the first calibration data set. The one or more processing units may be configured to determine second calibration depth values by correlating the three-dimensional data to the second calibration data set. The correlating may include comparing of three-dimensional data with the first and second calibration set in order to extract calibration depth values. The correlating may include interpolation of the calibration depth values based on the three-dimensional data in relation to the calibration data set.

[0009] The one or more processing units may be configured to determine, for the measured inner temperature, temperature corrected depth values of the dental object based on the first calibration depth values and the second calibration depth values.

[0010] The one or more processing units may be configured to determine, for the measured inner temperature, temperature corrected depth values of the dental object by an average of the first calibration depth values and the second calibration depth values.

[0011] The one or more processing units may be configured to determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0012] The one or more processing units may be configured to determine a three-dimensional model may be determined based on 2D images captured by the first image sensor, and wherein each of the 2D image includes the pixel positions and the corresponding pixel values. A temperature corrected depth value includes an amount which a depth value of a pixel should be corrected in relation to the measured inner temperature of the intraoral scanner. It is then seen, by applying the temperature correct depth values to the 3D model, the accuracy of the 3D model has improved significantly.The temperature sensor may be configured to measure the inner temperature during a scanning of the dental object, and during the scanning the inner temperature increases gradually. While the inner temperature increases the one or more processing units may be configured provide a temperature correction of the three-dimensional data. While the inner temperature increases the one or more processing units may be configured to determine the temperature corrected depth values of the dental object. The temperature correction of the depth values of the three-dimensional data may be performed in real time and while scanning the dental object. The advantage of performing the temperature correction of the depth values is that the intraoral scanner would provide three-dimensional data with an improved accuracy of the depth values.

[0013] The three-dimensional data may include a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner, the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, and the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner. The first image sensor, i.e. an image sensor, may include a plurality of pixels, and wherein each of the plurality of pixels is assigned to a pixel position, a depth configuration and / or a pixel intensity, i.e. a pixel value. The one or more processing units may be configured to determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depth configurations of the first calibration data set, and determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations of the second calibration data set.

[0014] The intraoral scanning system may be configured to determine three-dimensional data, i.e. depth values, from different focus lens positions at which maximum reflective intensity of light rays incident on the dental object being captured by the image sensor. In this example, the three-dimensional data, the first calibration data set, and the secondcalibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different positions of a focus lens of the intraoral scanner. The incident light rays may include a pattern. The intraoral scanning system provides an imaging of the pattern onto the dental object, and a focus plane may be adjusted in such a way that the image of the pattern on the dental object is shifted along an optical axis. The incident light incorporating the pattern provides a pattern of light and darkness on the dental object. Specifically, when the pattern is varied in time for a fixed focus plane then the in-focus regions on the object will display an oscillating pattern of light and darkness. The out-of-focus regions will display smaller or no contrast in the light oscillations. For a static pattern a single sub-scan can be obtained by collecting a number of 2D images at different positions of the focus plane. As the focus plane coincides with a scan surface of the dental object, the pattern will be projected onto the surface of the dental object in-focus and with high contrast. The high contrast gives rise to a large spatial variation of the static pattern on the surface of the object, thereby providing a large variation, or amplitude, of the pixel values over a group of adjacent pixels i.e. of the image sensor. For each pixels or group of pixels it is thus possible to identify individual settings of the focusing plane for which each pixels or group of pixels will be in focus. And these individual settings of the focusing plane is denoted as depth configurations. In one example, by using knowledge of the optical system used, it is possible to transform the contrast information vs. position of the focus plane into 3D surface information, on an individual pixel or pixel group basis.

[0015] In another example, intraoral scanning system may be configured to determine three-dimensional data, i.e. depth values, based on a triangulation principle. The intraoral scanner may include a light source and at least one image sensor, or two image sensors, that are pointed at a surface of the dental object. The image sensor(s) know the distance between themselves and the surface as well as the angle at which the light pattern is projected onto the dental object. To start the measurement with the pattern light projection, the dental object is placed on the surface. The light patterns are projected onto the dental object and deform based on the shape of the surface. These altered point or fringe patterns are detected by the image sensor(s), providing the information needed to calculate the distance from each point on the surface in the field of view of the image sensor(s). Thisresults in what is known as a point cloud (STL mesh), i.e. an accurate image of the measured object made up of many small measuring points.

[0016] The light source may project the pattern light of a first type to the dental object, and the image sensor may acquire 2D images of different viewpoints for the surface of the dental object to which the pattern light of the first type is projected. For example, the pattern light of the first type may include line pattern light.

[0017] A first point cloud data of the object may be determined based on the 2D images of the surface of the object to which the pattern light of the first type is projected and information about the pattern light of the first type. For example, the one or more processing units may determine which line of a 2D image scanned by a second image sensor corresponds to each line on the object shown in a 2D image scanned by a first image sensor. The one or more processing units may calculate 3D coordinates of points constituting each line matched between 2D images, based on the projected line pattern and a distorted line shown in the 2D images. The one or more processing units may obtain the first point cloud data by calculating 3D coordinates of each pixel included in the 2D images.

[0018] The light source may project the pattern light of a second type to the dental object, and the image sensor may acquire three-dimensional data of the surface of the dental object to which the pattern light of the second type is projected.

[0019] The light source may project the pattern light of the second type to the dental object, and the image sensor may be configured to acquire 2D images of different viewpoints for the surface of the dental object to which the pattern light of the second type is projected. For example, the pattern light of the second type may include point pattern light.

[0020] A second point cloud data of the object may be determined based on the 2D images of the surface of the dental object to which the pattern light of the second type is projected and information about the pattern light of the second type. For example, the one or more processing units may determine which point of a 2D image scanned by the second image sensor corresponds to each point of the object surface shown in a 2D image scanned by afirst image sensor. The one or more processing units may be configured to determine three-dimensional coordinates of each point matched between 2D images, based on the projected point pattern and a distorted point pattern shown in the 2D images. The one or more processing units may obtain the first point cloud data by calculating 3D coordinates of each pixel included in the 2D images. In the examples where the intraoral scanner is configured to determine he three-dimensional data based on a triangulation principle, the three-dimensional data acquired by the intraoral scanner, first calibration data set, and the second calibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different intersections of light rays with the plurality of pixel positions of the first image sensor. Which means that each pixels of the image sensor(s) may include information, such as points that constitute each line matched between 2D images, based on the projected line pattern and a distorted line shown in the 2D images.

[0021] The intraoral scanner includes a light source that may be configured to emit a probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different intersections of the probe light with the plurality of pixel positions, the first pixel positions and the second pixel positions, respectively, and another plurality of different intersections of the probe light with another plurality of pixel positions, another plurality of first pixel positions and another plurality of second pixel positions of a second image sensor of the intraoral scanner.

[0022] The intraoral scanner may include a light source configured to emit a patterned probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include structural measure of the patterned probe light that intersects the plurality of pixel positions, first pixel positions and the second pixel positions, respectively.

[0023] The intraoral scanning system may be configured to temperature correct the determined depth values according to calibration data set determined for different inner temperatures of the intraoral scanner. It has been shown that the quality of the depth values have improved significantly by only applying a first and a second calibration data set measuredat two different temperatures. The first calibration data set may be measured at a first temperature, and the second calibration data set may be measured at a second temperature. The second temperature may be more than 70 %, 60 %, 50 %, 40%, 30 %, 20 % warmer than the first temperature. For example, the second temperature may be around 60 degrees Celsius, and the first temperature may be around 35 degrees Celsius. To accommodate that the inner temperature of the intraoral scanner varies between different temperatures during a scanning of a patient, the weighted average may be determined by applying a first weighting coefficient to the first calibration depth values that are determined based on the first calibration data set, and applying a second weighting coefficient to the second calibration depth values that are determined based on the second calibration data set. The first and second weighting coefficients are determined based on the measured inner temperature of the intraoral scanner. While the intraoral scanner scans a patient, the first and second weighting coefficients are changing according to the inner temperature. Which means that the weighted average includes a first weighting coefficient assigned to the first calibration depth values, and a second weighting coefficient assigned to the second calibration depth values.

[0024] The three-dimensional data may include a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner, the first calibration data set may include a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, and the second calibration data set may include a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner. For example. The one or more processing units may be configured to determine the first calibration depth values by correlating the acquired three-dimensional data to the first calibration data set. The correlation may include interpolation or extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of first pixel positions and the corresponding first depth configurations. The one or more processing units may be configured to determine the second calibration depth values by correlating the acquired three-dimensional data to the second calibration data set. The correlation may include interpolation or extrapolation of a function determined by the plurality of pixel positions and the corresponding depthconfigurations along with the plurality of second pixel positions and the corresponding second depth configurations.

[0025] The plurality of pixel positions may include positions of pixels in a pixel array of the image sensor.

[0026] Each of the temperature corrected depth values may be determined by following formula:

[0027] CDcorrected(dc) = CD2(dc)W2+ CD^dc^

[0028] , wherein CDCOrrected is the temperature corrected depth value, CDi is a first calibration depth value of the first calibration depth values, CD2 is a second calibration depth value of the second calibration depth values, de is a depth configuration of depth configurations, and Wi and W2 are a first and a second weighting coefficient, respectively.

[0029] The first and second weighted coefficient may be determined by a temperature factor that relates to the measured inside temperature of the intraoral scanner. The temperature factor may be determined by following formula:

[0030]

[0031] f~ t2~ ti

[0032] , wherein tf is the temperature factor, ti is the measured inside temperature, ti is the first inner temperature, and t2 is the second inner temperature. The first weighting coefficient may be determined by following formula:

[0033] PVi = tf

[0034] , wherein tf is a temperature factor determined based on the measured inside temperature, and wherein the second weighting coefficient is determined by following formula:

[0035] W2= 1 - tf.

[0036] A sum of the first and second weighting coefficients may be constrained to a specific sum of one or higher.

[0037] The one or more processing units may be configured to determine, when the measured inside temperature is outside a temperature range determined by the first and second innertemperatures, the weighted average based on an extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations. The one or more processing units may be configured to determine, when the measured inside temperature is within the temperature range, the weighted average based on an interpolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations.

[0038] The memory unit may include a plurality of calibration data set measured at different temperatures of the intraoral scanner and based on the plurality of calibration data set a plurality of calibration depth values may be determined by correlating the acquired three-dimensional data to each of the plurality of calibration data set. In this example, the one or more processing units may be configured to determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the plurality of calibration depth values. The temperature corrected depth value of the temperature corrected depth values may be determined by following formula:

[0039] "corrected \U-C )

[0040]

[0041] , wherein CDCOrrected is the temperature corrected depth value, CD; is the plurality of calibration depth values, de is a depth configuration of depth configurations, and Wi is the weighting coefficient for each of the plurality of calibration depth values, respectively. In one example the sum of Wi may be one or higher.

[0042] In another example, the first calibration data set and the second calibration data set may be selected, based on the measured inner temperature, among the plurality of calibration data set. The selection of the first and second calibration data set may be based on the measured inner temperature and the inner temperature of the plurality of calibration data set. The measured inner temperature may be closest to the first and second inner temperature.

[0043] A calibration data set function may be determined based on the plurality of calibration data set. The one or more processing units may be configured to determine a plurality ofcalibration depth values based on the plurality of calibration data set, and wherein the temperature corrected depth values of the three-dimensional data may be determined, for the measured inner temperature, based on the calibration data set function. In one example, the chance in depth values according to the inner temperature may not be linearly, and thereby, the calibration data set function would provide a better accuracy than the weighted average approach.

[0044] The placement of the temperature sensor may be within the intraoral scanner, and more specifically, in vicinity to an image sensor, a light source, in a tip of the intraoral scanner. The temperature sensor may be arranged in vicinity to a component of the intraoral scanner that causes most changes to the depth values during chances of the inner temperature.

[0045] In another aspect, the disclosure relates to an intraoral scanning system that may be configured to determine temperature corrected depth values in three-dimensional data of a dental object. The intraoral scanning system may include an intraoral scanner configured to acquire, by a first image sensor, three-dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner, and the three-dimensional data includes a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner. The system may include a memory unit that includes a first calibration data set measured at a first inner temperature of the intraoral scanner, and wherein the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, and a second calibration data set measured at a second inner temperature of the intraoral scanner, and wherein the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature. The system may include one or more processing units configured to determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depthconfigurations, determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations, and determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0046] In a further aspect, the disclosure relates to a computer-implementable method for determining temperature corrected depth values in three-dimensional data of a dental object, wherein the method comprising acquiring three-dimensional data of a dental object, measuring an inner temperature of the intraoral scanner; determining a first calibration data set at a first inner temperature of the intraoral scanner, determining a second calibration data set at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and determining first calibration depth values by correlating the acquired three-dimensional data to the first calibration data set, determining second calibration depth values by correlating the three-dimensional data the second calibration data set, and determining, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0047] In yet another aspect, the disclosure relates to a computer-implemented method for determining temperature corrected depth values in three-dimensional data of a dental object, wherein the method comprising acquiring three-dimensional data of a dental object, and the three-dimensional data includes a plurality of pixel positions of a first image sensor and corresponding depth configurations of an intraoral scanner, measuring an inner temperature of the intraoral scanner, determining a first calibration data set at a first inner temperature of the intraoral scanner, and wherein the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, determining a second calibration data set at a second inner temperature of the intraoral scanner, and wherein the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, wherein the secondinner temperature is higher than the first inner temperature, and determining first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depth configurations, determining second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations, and determining, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0048] The dental object may be a tooth, a set of teeth, gingival, a jaw and / or both jaws of a patient.

[0049] The one or more processing units may be arranged in one or more elements of the intraoral scanning system:

[0050] • an intraoral scanner,

[0051] • an external computer that may be wired and / or wireless connected to the intraoral scanner,

[0052] • a local server, and / or

[0053] • a cloud server.

[0054] The intraoral scanner may include at least two image sensors configured to acquire the probe light.

[0055] The intraoral scanner may include at least two image sensors that are configured to acquire three-dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner.Due to temperature change in the intraoral scanner displacement of the probe light with the pattern can appear relative to the pixels of the image sensor of the intraoral scanner. The displacement of the probe light on the image sensor may appear in a horizontal or vertical directions relative to the image sensor(s). For example, a first part of the pattern in the probe light would on normal condition be captured by a first part of pixels of the first image sensor, but due to the displacement of the probe light, the first part of the pattern is then captured by a second part of the pixels of the image sensor. Whether the second part is displaced in the horizontal or vertical direction relative to the first part of the pixels depends on the design of the optical system in the intraoral scanner.

[0056] The displacement of the pattern relative to the pixels would cause inaccuracy in the three-dimensional data. To reduce this inaccuracy, the intraoral scanning system would be configured to reduce the inaccuracy (effect of the temperature change) in the three-dimensional by compensating for the displacement.

[0057] The disclosure relates to an intraoral scanning system configured to reduce displacement of a probe light relative to pixels of a first image sensor, wherein the system comprises an intraoral scanner configured to acquire, by the first image sensor, three-dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner, a memory unit that includes a measured curve that includes measured displacement of probe light relative to pixels of an image sensor of one or more other intraoral scanners, a first displacement relative to pixels of the first image sensor of the intraoral scanner measured at a first temperature, and a second displacement relative to pixels of the image sensor of the intraoral scanner measured at a second temperature, wherein the second temperature is higher than the first temperature. The intraoral scanning system includes one or more processing units configured to determine a displacement calibration curve based on the measured curve, the first and second displacements, and wherein the one or more processing units may be configured to determine corrected pixel positions of the pixels of the first image sensor for corresponding pixel values of the pixels. Additionally, the one or more processing units may be configured to correct pixel positions of the pixel values based on the determined corrected pixel positions to reducedisplacement in the probe light relative to the pixels. The probe light may be projected by a light source of the intraoral scanner.

[0058] The measured curve may be represented by a linear function or a polynomial function. The first and the second displacements and the corresponding first and second temperatures may be fitted to the linear function or the polynomial function.

[0059] The probe light may comprise a time-varying illumination pattern or a static pattern. The pattern may include a checkerboard pattern, a dot pattern or a line pattern.

[0060] The three-dimensional data may include a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner, the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner. The plurality of pixel positions of the three-dimensional data may be corrected based on the determined corrected pixel positions. The one or more processing units may be configured to determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depth configurations, and determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations.

[0061] BRIEF DESCRIPTION OF THE FIGURES

[0062] 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, featuresand / or technical effect will be apparent from and elucidated with reference to the illustrations described hereinafter in which:

[0063] FIG. 1 illustrates an example of an intraoral scanning system,

[0064] FIGS. 2A and 2B illustrate an example of three-dimensional data,

[0065] FIGS. 3A and 3B illustrate an example of three-dimensional data,

[0066] FIG. 4 illustrates an example of three-dimensional data,

[0067] FIG. 5 illustrates yet an example of three-dimensional data,

[0068] FIG. 6 illustrates an example of measured molar-to-molar distance,

[0069] FIGS. 7 A and 7B illustrate examples on how temperature corrected depth values are determined, and

[0070] FIG. 8 illustrates a computer-implementable method for determining temperature corrected depth values in three-dimensional data of a dental object.

[0071] DETAILED DESCRIPTION

[0072] 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”).

[0073] Depending upon particular application, design constraints or other reasons, these elements may be implemented using electronic hardware, computer program, or any combination thereof.

[0074] 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 ofexecution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0075] A scanning for providing intra-oral scan data may be performed by a dental scanning system that may include an intraoral scanner, 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 intraoral scanner 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 by 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 each 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 several 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, 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 ClosestPoint (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 plurality of dental objects 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.

[0076] The dental scanning system may be an intraoral scanning system. The scanning device may be an intraoral scanning device.

[0077] Color texture of the plurality of dental objects may be acquired by illuminating the object using different monochromatic colors such as individual red, green and blue colors or my illuminating the object using multi chromatic light such as white light. A 2D image may be acquired during a flash of white light.

[0078] Generally, the process of obtaining surface information in real time of the plurality of dental objects 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 300-20002D 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 eighter 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.

[0079] The scanning device comprises one or more light projectors configured to generate an illumination pattern to be projected on a three-dimensional dental object during a scanning session. The light projector(s) preferably comprises a light source, a mask signal 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 object. 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 signal projectors, wherein the light source is placed behind a mask signal having a spatial pattern, whereby the light projected on the surface of the dental object is patterned. The back-lit mask signal 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 signal. The mask signal may have a checkerboard pattern, such that the generated illumination pattern is a checkerboard pattern. Alternatively, the mask signal may feature other patterns such as lines or dots, etc.

[0080] The scanning device preferably further comprises optical components for directing the light from the light source to the surface of the dental object. 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 2442720 Bl by the same applicant, which is incorporated herein in its entirety.

[0081] The light reflected from the dental object in response to the illumination of the dental object 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 object. 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 acolor 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.

[0082] 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.

[0083] 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 object. 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 object. 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 object in response to illuminating saidobject 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.

[0084] FIG. 1 illustrates an example of an intraoral scanning system 1 that is configured to determine temperature corrected depth values 9 in three-dimensional data 4 of a dental object 11. The intraoral scanning system includes an intraoral scanner 10 that is configured to acquire, by a first image sensor 12, three-dimensional data 4 of a dental object 11, wherein the three-dimensional data 4 is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor 13 of the intraoral scanner 10. In another example, the intraoral scanning system 1 includes a plurality of image sensors that is configured to acquire three-dimensional data 4 of the dental object 11. In the present example the first image sensor 12 is arranged in a main body of the intraoral scanner. In another example, the first image sensor 12 could be arranged in the tip of the intraoral scanner 10. The temperature sensor 13 may be arranged in vicinity to the image sensor 12. In another example, the temperature sensor 13 may be arranged in the tip of the intraoral scanner 10 or in vicinity of a power supplier of the intraoral scanner 10. In yet another example, the temperature sensor 13 is arranged in vicinity of the mechanical structure ofthe optical system. The system 1 includes a memory unit 2 that includes a first calibration data set 6 measured at a first inner temperature of the intraoral scanner 10, and a second calibration data set 6 measured at a second inner temperature of the intraoral scanner 10, wherein the second inner temperature is higher than the first inner temperature. In this example the memory is arranged outside the intraoral scanner 10. In another example, the memory unit 2 is arranged within the intraoral scanner 10. In yet another example, the memory unit 2 may be divided into multiple sub memory units that are arranged partly within and outside the intraoral scanner. The memory unit or the sub memory units that are arranged outside the intraoral scanner may form part of a cloud server, a local server, an external computer etc. The system 1 includes one or more processing units 5 configured to determine first calibration depth values 8 by correlating the acquired three-dimensional data 4 to the first calibration data set 6. The one or more processing units 5 is further configured to determine second calibration depth values 7 by correlating the three-dimensional data 4 to the second calibration data set 6, and determine, for the measured inner temperature 3, temperature corrected depth values 9 of the dental object 11 by a weighted average (or extrapolation) of the first calibration depth values 8 and the second calibration depth values 7.

[0085] FIGS. 2A and 2B illustrate an example of the three-dimensional data 4 which in the present example is a sub-scan that includes a plurality of pixels (Pl 1 - P23), wherein each of the plurality of pixels includes a pixel position (Pl 1 - P23) and a depth configuration (Pl, P2, P3). In this example, the depth configuration (Pl, P2, P3) is a position of a focus lens (20A, 20B, 20C) of the intraoral scanner 10. In this example, the focus lens (20 A, 20B, 20C) is movable along an optical axis 21. The sub-scan 4 includes a plurality of pixels that has different depth configurations (Pl, P2, P3) as the sub-scan 4 includes a composition of pixels from different 2D images (4A, 4B, 4C) acquired by the image sensor 12 when the focus lens (20A, 20B, 20C) is positioned differently along the optical axis 21. In this example, the sub-scan 4 includes a first group of pixels from a first 2D image 4A that has a first depth configuration Pl, a second group of pixels from a second 2D image 4B that has a second depth configuration P2, and a third group of pixels from a third 2D image 4C that has a third depth configuration P3. Each of the plurality of pixels may have a pixel value (Il - 16).FIGS. 3 A and 3B illustrate an example of the three-dimensional data 4 which in the present example is a 2D image 4 captured at a certain focus position (Pl, P2, P3) of the focus lens (20 A, 20B, 20C). The 2D image 4 includes a plurality of pixels (Pl 1 - P23), wherein each of the plurality of pixels includes a pixel position (Pl 1 - P23) and a depth configuration (Pl, P2, P3). In this example, the depth configuration (Pl, P2, P3) is a position of the focus lens (20 A, 20B, 20C) of the intraoral scanner 10. Furthermore, the focus lens (20A, 20B, 20C) is movable along an optical axis 21. The 2D image 4 includes a plurality of pixels that has the same depth configuration (Pl, P2, P3). Each of the plurality of pixels of the 2D image 4 may have a pixel value (Il - 16), depth configuration, i.e. a position of the focus lens (Pl, P2, P3), and / or a pixel position (Pl 1 - P23).

[0086] FIG. 4 illustrates an example of the three-dimensional data (4A, 4B, 4C) determined based on a triangulation principle of the intraoral scanner 10. The intraoral scanner 10 includes a light source that is configured to emit a patterned probe light 40 which in this example includes a time-varying line pattern (41 A, 41B, 41C). The one or more processing units 5 is configured to determine the three-dimensional data 4 based on pixel positions (Pl 1 -P23) and corresponding structural measure (SI, S2, S3) of the time-varying line pattern (41A, 41B, 42C). The depth configurations include structural measure (SI, S2, S3) of the patterned probe light 40 that intersects the plurality of pixel positions (Pl 1 - P23). In the present examples, three different 2D images (4A, 4B, 4C) are seen with different structural measures (SI, S2, S3) of the time-varying line pattern (41, 4 IB, 41C).

[0087] FIG. 5 illustrate an example of the three-dimensional data 4 determined based on a triangulation principle of the intraoral scanner 10. In this example, the intraoral scanner 10 includes two image sensors that are configured to capture 2D images (4A, 4B) of the dental object 11 from different angles. In this example, the depth configurations include a plurality of different intersections of the probe light with the plurality of pixel positions (Pl 1 - P23) of a first 2D image 4 A. The first 2D image 4 A is captured by a first image sensor 12 A. Furthermore, the depth configurations include another plurality of different intersections of the probe light with another plurality of pixel positions of a second 2D image 4B. The second 2D image is captured by a second image sensor 12B of the intraoralscanner 10. Each of the plurality of pixel positions of the three-dimensional data 4 includes correspondence pixel positions of the first and second 2D images (4A, 4B), wherein the correspondence pixel positions include 2D image data of the same area of the dental object 11 but with a different angle 50 between the respective image sensors (12A, 12B) and the dental object 11.

[0088] FIG. 6 illustrate an example of measured molar-to-molar distance 61 that have been provided by a three-dimensional model of a dental object, such as a jaw, and wherein the three-dimensional model includes depth values determined when the inner temperature is around 35 degree Celsius 63, and when the inner temperature is around 60 degree Celsius 64, and when three-dimensional model includes temperature corrected depth values 65. The molar-to-molar distance 61 is a measure between two opposite molars of a jaw during multiple scans 62. It is seen that when the inner temperature is around 35 degrees Celsius 63, the molar-to-molar distance 61 is changing when adding more scans 62 to the 3D model of the dental object as the temperature inside the intraoral scanner changes.

[0089] Furthermore, it is seen that when the inner temperature is around 60 degrees Celsius 64 the molar-to-molar distance 61 is changing when adding more scans 62 to the 3D model of the dental object while the temperature inside the intraoral scanner is changing, and wherein the measured molar-to-molar distance is higher when the temperature is around 35 degrees Celsius 63. The change in distance which is caused by the temperature change inside the intraoral scanner is unwanted. It is then seen, that when applying the temperature correct depth values to the 3D model, the accuracy of the measured molar-to-molar distance has increased significantly. That is seen by the change in the measured molar-to-molar distance that has decreased significantly over the period of multiple scans.

[0090] FIGS. 7 A and 7B illustrate examples on how the temperature corrected depth values CDcorrected) are determined. The temperature corrected depth value CDcorrected) of the temperature corrected depth values is determined by following formula:

[0091] CDcorrected(dc) = CD2(dc)W2+ CD^dc^

[0092] , wherein CDCOrrected is the temperature corrected depth value, CDi is a first calibration depth value of the first calibration depth values, CD2 is a second calibration depth value of the second calibration depth values, de is a depth configuration, and Wi and W2 are a firstand a second weighting coefficient, respectively. In the example illustrated in FIG. 7A, the first and second calibration depth value (CDi, CD2) are determined based on the first and second calibration data set (CDS1, CDS2), respectively. In this present example, the first and second calibration value (CDI, CD2) are determined by interpolation or extrapolation based on the plurality of pixel positions (Pxx) and depth configurations (de). The temperature corrected depth value CDCOrrected of one or more pixel positions (Pxx) is determined by the equation 71 based on the determined calibration depth values (CDI, CD2). In both FIGS. 7A and 7B the weighting coefficients (Wi, W2) are determined based on the measured inner temperature (ti,3). FIG. 7B illustrates an example on how the weighting coefficients (Wi, W2) are determined. In the example, tf is the first weighting coefficient is equal to a temperature factor tf that is determined based on the measured inside temperature ti, a first inner temperature ti (that corresponds to the temperature where the first calibration depth values are determined) and a second inner temperature t2 (that corresponds to the temperature where the second calibration depth values are determined).

[0093] FIG. 8 illustrates a computer-implementable method 100 for determining temperature corrected depth values in three-dimensional data of a dental object, wherein the method comprising 100 acquiring 100A three-dimensional data of a dental object, measuring 100B an inner temperature of the intraoral scanner, determining 100C a first calibration data set at a first inner temperature of the intraoral scanner, determining 100D a second calibration data set at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, determining 100E first calibration depth values by correlating the acquired three-dimensional data to the first calibration data set, determining 100F second calibration depth values by correlating the three-dimensional data the second calibration data set, and determining 100G, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values. The order of the steps 100A to 100D is irrelevant and so is it between the steps 100E and 100F.

[0094] In an example of the method 100, the three-dimensional data includes a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoralscanner, the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, and the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner. In this example, the one or more processing units 5 is configured for determining first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depth configurations, and determining second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations.

[0095] Due to temperature change in the intraoral scanner displacement of the probe light with the pattern can appear relative to the pixels of the image sensor of the intraoral scanner. The displacement of the probe light on the image sensor may appear in a horizontal or vertical directions relative to the image sensor(s). For example, a first part of the pattern in the probe light would on normal condition be captured by a first part of pixels of the first image sensor, but due to the displacement of the probe light, the first part of the pattern is then captured by a second part of the pixels of the image sensor. Whether the second part is displaced in the horizontal or vertical direction relative to the first part of the pixels depends on the design of the optical system in the intraoral scanner.

[0096] The displacement of the pattern relative to the pixels would cause inaccuracy in the three-dimensional data. To reduce this inaccuracy, the intraoral scanning system would be configured to reduce the inaccuracy (effect of the temperature change) in the three-dimensional by compensating for the displacement. The displacement of the probe light relative to pixels of the first image sensor is determined at different temperatures, see FIG. 9. It is clearly seen that when the temperature 67 increases throughout a scanning of a patient the displacement 66 increases and that causes inaccuracy in the depth values of a three-dimensional model. The behaviour of the displacement 66 relative to the temperature 67 is assumed to be equivalent for any similar intraoral scanners 10, and to simplify the calibration method of a single intraoral scanner 10, of similar type, a firstand a second calibration measures of the displacement is done, f.x. at 35 °C and 60 °C. Which means, for a single intraoral scanner, the first displacement is measured at a first temperature, e.g. at 35 °C, and then the second displacement is measured at a second temperature, e.g. at 60 °C, and a measured curve, similar to the curve in FIG. 9, is then fitted to the measured first and second displacements and the corresponding first and second temperatures for the specific intraoral scanner 10. Thereby, instead of performing several measures of the displacement between the first and the second temperature, e.g. a minimum and a maximum temperature, two measures are performed. That would lower the calibration time of an intraoral scanner 10 significantly.

[0097] FIGS. 10A, 10B and 10C illustrates the displacement of the pattern 41 relative to pixels of an image sensor 12. In the examples, a light source 92 projects a pattern 41 towards a dental object 11 which is then reflected and captured by the image sensor 12. In FIG. 10A, the inner temperature T1 of the intraoral scanner 10 is at an ideal temperature, such as 25 °C. In this example, a first column of pixels PCI receives a part of the projected pattern 41, and in FIG. 10B, the inner temperature T2 has increased and a displacement of the pattern 41 relative to the pixels is seen as a similar part of the pattern 41 is instead received by a second column of pixels PC2. In. FIG. 10C, the one or more processing units 5 performs a correction of the displacement, such that when the depth values of the three-dimensional model is determined, the received pattern would be interpreted as being received by the first column instead of the second column. That would result in a more accurate 3D model of the dental object 11.

[0098] FIGS. 11A, 1 IB and 11C illustrate examples of how the temperature corrected depth values is determined, how the displacement is corrected, and how both the temperature corrected depth values and displacement correction are combined. The one or more processing units of the intraoral scanner 10 is configured to perform the examples illustrated in FIGS. 11 A, 1 IB and 11C. In FIG. 11 A, pixel positions (Pxx) and corresponding pixel values (Vai, Il - 16) are received 110A along with pixel positions (Pxx) and corresponding depth configurations (de) HOB. First and second calibration depth values (CD1, CD2) are then determined 110C, which is then used to determine 110E the temperature corrected depth values CD corrected at the measured innertemperature T HOD. The depth values determined based on the received 2D images are then corrected by the temperature corrected depth values 110F. The correction may imply replacing the depth values with the temperature corrected depth values or by correcting the depth values with the temperature corrected depth values through subtraction, summation or another mathematical operation.

[0099] FIG. 1 IB illustrates an example of correcting the displacement of the projected pattern 41 relative to pixels of the image sensor 12. First a measured curve (MC) of displacement relative to a plurality of temperatures is received 11 A, wherein the plurality of temperatures includes more than 2 different temperatures, preferably more than 8 different temperatures. The measured curve MC may include averaged displacements relative to a plurality of temperatures measured on numerous of similar intraoral scanners. In another example, the measured curve MC may include displacements relative to a plurality of temperatures measured on a similar intraoral scanner. For the specific intraoral scanner 10, a first displacement DPI is measured 111 A at a first temperature, e.g. at 35 °C, and a second displacement DP2 is measured 111A at a second temperature, e.g. at 60 °C, and a displacement calibration curve DCC for the specific intraoral scanner 10 is determined 1 IB based on the first and second displacements (DPI, DP2) along with the measured curve MC. Via the displacement calibration curve DCC and the measured inner temperature T of the intraoral scanner a displacement of the probe light, i.e. the pattern 41, is determined 11 ID and then used to correct 11 IE the pixel positions PXX for the corresponding pixel values (val, Il-I6)and the corresponding depth configurations (cd).

[0100] FIG. 11C illustrates an example where the corrected pixel positions (PP cor) is used when determining the temperature corrected depth values (CD corrected) 110E.

[0101] ITEMS

[0102] 1. An intraoral scanning system configured to determine temperature corrected depth values in three-dimensional data of a dental object, wherein the intraoral scanning system includes:• an intraoral scanner configured to acquire, by a first image sensor, three- dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner,

[0103] • a memory unit that includes:

[0104] o a first calibration data set measured at a first inner temperature of the intraoral scanner,

[0105] o a second calibration data set measured at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and

[0106] • one or more processing units configured to:

[0107] o determine first calibration depth values by correlating the acquired three- dimensional data to the first calibration data set,

[0108] o determine second calibration depth values by correlating the three- dimensional data the second calibration data set, and

[0109] o determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0110] 1 A. An intraoral scanning system configured to determine temperature corrected depth values in three-dimensional data of a dental object, wherein the intraoral scanning system includes:

[0111] • an intraoral scanner configured to acquire, by a first image sensor, three- dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner, and the three-dimensional data includes a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner,

[0112] • a memory unit that includes:

[0113] o a first calibration data set measured at a first inner temperature of the intraoral scanner, and wherein the first calibration data set includes aplurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner,

[0114] o a second calibration data set measured at a second inner temperature of the intraoral scanner, and wherein the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and

[0115] • one or more processing units configured to:

[0116] o determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three- dimensional data to the plurality of first pixel positions and the corresponding first depth configurations,

[0117] o determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three- dimensional data to the plurality of second pixel positions and the corresponding second depth configurations, and

[0118] o determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values. he intraoral scanning system according to item 1, wherein:

[0119] • the three-dimensional data includes a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner,

[0120] • the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner, • the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, and

[0121] wherein the one or more processing units is configured to:

[0122] • determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three-dimensional data to the plurality of first pixel positions and the corresponding first depth configurations, and

[0123] • determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations.

[0124] 3. The intraoral scanning system according to item 1, wherein the three-dimensional data, the first calibration data set, and the second calibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different positions of a focus lens of the intraoral scanner.

[0125] 4. The intraoral scanning system according to item 1, wherein the three-dimensional data, the first calibration data set, and the second calibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different intersections of light rays with the plurality of pixel positions of the first image sensor.

[0126] 5. The intraoral scanning system according to item 2, wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different positions of a focus lens of the intraoral scanner.

[0127] 6. The intraoral scanning system according to item 2, wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different intersections of light rays with the plurality of pixel positions, the first pixel positions, and the second pixel positions, respectively.

[0128] 7. The intraoral scanning system according to item 5, wherein the intraoral scanner includes a light source configured to emit a probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different intersections of the probe light with the plurality of pixel positions,the first pixel positions and the second pixel positions, respectively, and another plurality of different intersections of the probe light with another plurality of pixel positions, another plurality of first pixel positions and another plurality of second pixel positions of a second image sensor of the intraoral scanner.

[0129] 8. The intraoral scanning system according to item 6, wherein the intraoral scanner includes a light source configured to emit a patterned probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include structural measure of the patterned probe light that intersects the plurality of pixel positions, first pixel positions and the second pixel positions, respectively.

[0130] 9. The intraoral scanning system according to any of the previous items, wherein the weighted average includes:

[0131] • a first weighting coefficient assigned to the first calibration depth values, and • a second weighting coefficient assigned to the second calibration depth values.

[0132] 10. The intraoral scanning system according to item 2, wherein:

[0133] • for the first calibration depth values, the correlation includes interpolation or extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of first pixel positions and the corresponding first depth configurations, and

[0134] • for the second calibration depth values, the correlation includes interpolation or extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations.

[0135] 11. The intraoral scanning system according to any of the previous items, wherein the temperature corrected depth value of the temperature corrected depth values is determined by following formula:

[0136] CDcorrected(dc) = CD2(dc)W2+ CD^dc^, wherein CDCOrrected is the temperature corrected depth value, CDi is a first calibration depth value of the first calibration depth values, CD2 is a second calibration depth value of the second calibration depth values, de is a depth configuration of depth configurations, and Wi and W2 are a first and a second weighting coefficient, respectively.

[0137] 12. The intraoral scanning system according to any of the previous items, wherein the weighted average includes a first and a second weighting coefficient assigned to the first and second first calibration depth value, respectively, and wherein the first and second weighted coefficient are determined by a temperature factor that relates to the measured inside temperature of the intraoral scanner.

[0138] 13. The intraoral scanning system according to item 12, wherein a sum of the first and second weighting coefficients are constrained to a specific sum of one or higher.

[0139] 14. The intraoral scanning system according to any of items 12 and 13, wherein the temperature factor is determined by following formula:

[0140]

[0141] f~ t2~ h

[0142] , wherein tf is the temperature factor, ti is the measured inside temperature, ti is the first inner temperature, and t2 is the second inner temperature.

[0143] 15. The intraoral scanning system according to any of items 11 to 14, wherein the first weighting coefficient is determined by following formula:

[0144]

[0145] = tf

[0146] , wherein tf is a temperature factor determined based on the measured inside temperature, and wherein the second weighting coefficient is determined by following formula:

[0147] W2= 1 - tf.

[0148] 16. The intraoral scanning system according to item 2, wherein, the one or more processing units is configured to:• determine, when the measured inside temperature is outside a temperature range determined by the first and second inner temperatures, the weighted average based on an extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations, and

[0149] • determine, when the measured inside temperature is within the temperature range, the weighted average based on an interpolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations.

[0150] 17. A computer-implementable method for determining temperature corrected depth values in three-dimensional data of a dental object, wherein the method comprising:

[0151] • acquiring three-dimensional data of a dental object,

[0152] • measuring an inner temperature of the intraoral scanner,

[0153] • determining a first calibration data set at a first inner temperature of the intraoral scanner,

[0154] • determining a second calibration data set at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and

[0155] • determining first calibration depth values by correlating the acquired three- dimensional data to the first calibration data set,

[0156] • determining second calibration depth values by correlating the three-dimensional data the second calibration data set, and

[0157] • determining, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

[0158] 18. A computer-implemented method for determining temperature corrected depth values in three-dimensional data of a dental object, wherein the method comprising:• acquiring three-dimensional data of a dental object, and the three-dimensional data includes a plurality of pixel positions of a first image sensor and corresponding depth configurations of an intraoral scanner,

[0159] • measuring an inner temperature of the intraoral scanner,

[0160] • determining a first calibration data set at a first inner temperature of the intraoral scanner, and wherein the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner,

[0161] • determining a second calibration data set at a second inner temperature of the intraoral scanner, and wherein the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and

[0162] • determining first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three- dimensional data to the plurality of first pixel positions and the corresponding first depth configurations,

[0163] • determining second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations, and

[0164] • determining, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

Claims

AMENDED CLAIMSreceived by the International Bureau on 06 July 2026 (06.07.2026)CLAIMS1. An intraoral scanning system configured to determine temperature corrected depth values in three-dimensional data of a dental object, wherein the intraoral scanning system includes:• an intraoral scanner configured to acquire, by a first image sensor, three- dimensional data of a dental object, wherein the three-dimensional data is acquired at an inner temperature of the intraoral scanner measured by a temperature sensor of the intraoral scanner,• a memory unit that includes :o a first calibration data set measured at a first inner temperature of the intraoral scanner,o a second calibration data set measured at a second inner temperature of the intraoral scanner, wherein the second inner temperature is higher than the first inner temperature, and• one or more processing units configured to:o determine first calibration depth values for the acquired three-dimensional data by correlating the acquired three-dimensional data to the first calibration data set,o determine second calibration depth values for the acquired three- dimensional data by correlating the three-dimensional data to the second calibration data set, ando determine, for the measured inner temperature, temperature corrected depth values of the dental object by a weighted average of the first calibration depth values and the second calibration depth values.

2. The intraoral scanning system according to claim 1, wherein:• the three-dimensional data includes a plurality of pixel positions of the first image sensor and corresponding depth configurations of the intraoral scanner,• the first calibration data set includes a plurality of first pixel positions of the first image sensor and corresponding first depth configurations of the intraoral scanner,• the second calibration data set includes a plurality of second pixel positions of the first image sensor and corresponding second depth configurations of the intraoral scanner, andwherein the one or more processing units is configured to:• determine first calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the acquired three- dimensional data to the plurality of first pixel positions and the corresponding first depth configurations, and• determine second calibration depth values by correlating the plurality of pixel positions and the corresponding depth configurations of the three-dimensional data to the plurality of second pixel positions and the corresponding second depth configurations.

3. The intraoral scanning system according to claim 1, wherein the three-dimensional data, the first calibration data set, and the second calibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different positions of a focus lens of the intraoral scanner.

4. The intraoral scanning system according to claim 1, wherein the three-dimensional data, the first calibration data set, and the second calibration data set are determined based on different depth configurations of the intraoral scanner, wherein the different depth configurations include a plurality of different intersections of light rays with a plurality of pixel positions of the first image sensor.

5. The intraoral scanning system according to claim 2, wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different positions of a focus lens of the intraoral scanner.

6. The intraoral scanning system according to claim 2, wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality ofdifferent intersections of light rays with the plurality of pixel positions, the first pixel positions, and the second pixel positions, respectively.

7. The intraoral scanning system according to claim 5, wherein the intraoral scanner includes a light source configured to emit a probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include a plurality of different intersections of the probe light with the plurality of pixel positions, the first pixel positions and the second pixel positions, respectively, and another plurality of different intersections of the probe light with another plurality of pixel positions, another plurality of first pixel positions and another plurality of second pixel positions of a second image sensor of the intraoral scanner.

8. The intraoral scanning system according to claim 6, wherein the intraoral scanner includes a light source configured to emit a patterned probe light, and wherein the depth configurations, the first depth configurations, and the second depth configurations include structural measure of the patterned probe light that intersects the plurality of pixel positions, first pixel positions and the second pixel positions, respectively.

9. The intraoral scanning system according to any of the previous claims, wherein the weighted average includes:• a first weighting coefficient assigned to the first calibration depth values, and • a second weighting coefficient assigned to the second calibration depth values.

10. The intraoral scanning system according to any of the previous claims, wherein the temperature corrected depth value of the temperature corrected depth values is determined by following formula:CDcorrecteddc) = CD2(dc)W2+ CD1dc')W1, wherein CD corrected is the temperature corrected depth value, CDi is a first calibration depth value of the first calibration depth values, CD2 is a second calibration depth value of the second calibration depth values, de is a depth configuration of depth configurations, and Wi and W2 are a first and a second weighting coefficient, respectively.

11. The intraoral scanning system according to any of the previous claims, wherein the weighted average includes a first and a second weighting coefficient assigned to the first and second first calibration depth value, respectively, and wherein the first and second weighted coefficient are determined by a temperature factor that relates to the measured inside temperature of the intraoral scanner.

12. The intraoral scanning system according to claim 11, wherein a sum of the first and second weighting coefficients are constrained to a specific sum of one or higher.

13. The intraoral scanning system according to any of claims 11 and 12, wherein the temperature factor is determined by following formula:tj -ft2~ ti, wherein tf is the temperature factor, ti is the measured inside temperature, ti is the first inner temperature, and t2 is the second inner temperature.

14. The intraoral scanning system according to any of items 10 to 13, wherein the first weighting coefficient is determined by following formula:W1 =tf, wherein tf is a temperature factor determined based on the measured inside temperature, and wherein the second weighting coefficient is determined by following formula:<IMG file=null he=null id=imgf000042_0001 img-content=null img-format=null inline=null orientation=null wi=null>= 1 - tf.

15. The intraoral scanning system according to claim 2, wherein, the one or more processing units is configured to:• determine, when the measured inside temperature is outside a temperature range determined by the first and second inner temperatures, the weighted average based on an extrapolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations, anddetermine, when the measured inside temperature is within the temperature range, the weighted average based on an interpolation of a function determined by the plurality of pixel positions and the corresponding depth configurations along with the plurality of second pixel positions and the corresponding second depth configurations.

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