Apparatus and method for performing intraoral scans

Abstract

The present invention relates to a method and device for creating three-dimensional images using an intraoral scanning device. In the method according to the present invention, a color pattern (111, 112, 113) is projected onto the surface to be captured, in particular onto a tooth (40). During the projection, multiple images are recorded using at least three cameras (13) spaced apart from one another and arranged in a plane on the scanning device. A depth map can be directly calculated by the displacement of corresponding pixels. In a subsequent step, the calculated depth maps are merged, and finally, a 3D model is calculated. The essence of the invention is that the projected color pattern generates an intensity profile that is as continuous as possible in the individual color channels, and matching pixels or patterns are detected by evaluating vector differences in color space. The color pattern is projected intermittently. A new solution needs to be invented to achieve high light intensity microprojection during flash operation.

Description

[Technical Field]

[0001] The present invention relates to a method for capturing depth data within a patient's mouth, as well as an apparatus for performing these scans and generating a 3D model of the captured area. [Background technology]

[0002] Such devices are also called intraoral scanners. By creating a 3D model of the scanned area inside a patient's mouth, teeth, dentures, crowns, and bridges can be displayed, allowing dental products to be fabricated without taking traditional impressions using impression materials. Previously required intermediate steps, such as creating plaster models and using extraoral scanning systems, can be eliminated with intraoral scanning.

[0003] The 3D models obtained from the intraoral scans can then be used in the computer-aided manufacturing of dental prostheses such as crowns or bridges, or for computer-aided dental diagnosis, which is a growing market.

[0004] A variety of different methods and devices for performing intraoral scans are available on the market, and all of the different methods have advantages and disadvantages.

[0005] One possibility for capturing distance data is triangulation. Here, it is possible to perform distance measurements using only the camera and the projected pattern. The single-camera approach requires calibrating the correspondence between the pattern projected by the light source, e.g., stripes, and the stripes observed in the image.

[0006] Generally, the pattern captured by the camera will differ from the projected pattern due to different optical properties of the scanned object or material. This is especially true for teeth. For example, the pattern may have sharp edges, making accurate triangulation and assignment to the pattern more difficult.

[0007] In order to be able to calculate as much depth information as possible, it is necessary to display and evaluate as many lines as possible. The problem here is that, on the one hand, the number of lines that can be evaluated is limited by the optical properties of the teeth, and, on the other hand, it is no longer possible to establish an assignment to the projected lines. To ensure an assignment to the projected lines, several images with stripes of different widths are usually taken and evaluated, which has the disadvantage that the intraoral scanner moves between images, which must be taken into account in the evaluation. Known alternative methods would be to code the stripes or use colored stripes, although these may not be suitable due to the properties of the teeth.

[0008] Another technique is stereo vision, which uses two cameras to enable spatial viewing. However, it should be noted that there are also triangulation methods that use two cameras.

[0009] US Patent No. 5,949,999 describes an intraoral scanner that operates with at least one camera, and is therefore essentially a triangulation-based scanner.

[0010] The basic principle of stereo vision is that the same point on the object being scanned is recorded by at least two cameras from different "viewing directions". The disparity thus detected can be used to generate a depth map and ultimately a 3D image of the object being scanned. As with triangulation, there are many different types of stereo vision.

[0011] For example, there are active stereo vision and passive stereo vision. In contrast to active stereo vision, passive stereo vision does not require light to be projected onto the object being scanned.

[0012] In active stereo vision, optical projection is used to project a pattern onto the object being scanned, which allows for a clearer and more accurate determination of disparity, so random patterns are often used here.

[0013] In particular, teeth are also wet in the patient's mouth and exhibit many optical effects related to partial translucency. Finely structured random patterns can no longer be clearly recognized. Therefore, a pattern is needed that is as clear as possible on the teeth and allows image sections from the left and right images to match.

[0014] One possibility is to use colors and color gradients in addition to black and white patterns, which makes color discrimination much easier and allows for good matching. The use of color stripes allows for maximum contrast.

[0015] The arrangement of the camera, projector and overall geometry, particularly the distal section of the scanning device that is inserted into the patient's oral cavity, is designed differently depending on the known intraoral scanner and is often adapted to the scanning method used in each case.

[0016] It must be taken into account that, compared to other known 3D scanning methods, the geometric and optical characteristics of the patient's intraoral cavity pose high technical obstacles, and the distal part of the intraoral scanner must be very small. For this purpose, special solutions for intraoral scanners have been developed in the prior art.

[0017] US Patent No. 5,949,999 describes an intraoral scanner having multiple cameras arranged alternately with light projectors on the device.

[0018] US Pat. No. 5,629,999 describes a scanning device that partially encloses the teeth during scanning. [Prior art documents] [Patent documents]

[0019] [Patent Document 1] International Publication WO2019 / 085402(A1) [Patent Document 2] European Patent Application Publication No. 2166303 [Patent Document 3] International Publication WO2016 / 142917(A1) Summary of the Invention [Problem to be solved by the invention]

[0020] The object of the present invention is to provide an improved scanner and an improved device of the type mentioned in the introduction, which allow fast and accurate scanning. Due to the placement of the camera and projector in the distal area of ​​the intraoral scanner, they are limited in size. In order to realize a microprojector, new solutions need to be found. [Means for solving the problem]

[0021] According to the invention, this problem is solved by a scanning method according to claim 1 and a scanning device according to claim 11. The dependent claims represent preferred embodiments of the invention. The scanning device is used in particular for scanning one or more teeth.

[0022] In a first step of the method according to the invention, a color pattern or a color stripe pattern is projected onto the surface of the tooth to be scanned, preferably using at least one projector. While the color pattern is being projected onto the tooth surface, groups of images are simultaneously recorded, either consecutively or at short intervals, using at least three cameras arranged in a plane and laterally spaced apart from one another.

[0023] The plurality of images includes a plurality of image groups, and the images of each image group are recorded simultaneously.

[0024] This plurality of images is then, or successively, transferred to a data processor. If desired, only certain information from these images can be transferred to the data processor. This variant is preferably included in the concept of transferring images to a data processor.

[0025] The data processor compares at least two of the three simultaneously captured images. These two images are hereafter referred to as an image pair. The images are compared using an algorithm designed to recognize corresponding patterns in the image pair.

[0026] Corresponding patterns are individual image pixels or areas of pixels in an image pair that are offset from each other. Depth can be calculated directly from the offsets (disparity) of the pattern / image pixels in the image pair in the form of a depth map. By aligning the cameras, the search space for corresponding pixels can be reduced to a line.

[0027] In the final step, the depth maps generated from the images in the image group are merged to finally form the 3D model.

[0028] The present method also differs from the prior art in that the generated color pattern projected onto the teeth and captured by the camera has a predominantly continuous intensity gradient in each color channel. Matching pixels or patterns are then identified by analysis in color space. Matching pixels are determined by comparing the direction and length of color vectors in color space.

[0029] Continuity helps reduce noise in the image.

[0030] In the context of the present invention, "mainly continuous" means that jumps may occur due to shading of the projection pattern.

[0031] Preferably, at least two image pairs are formed from each image group and inspected for corresponding patterns. Thus, by calculating the disparity, at least two depth maps can be generated. The depth maps overlap due to the camera placement. The depth map is calculated from the at least two depth maps, thereby evaluating and improving the quality of points in the overlapping area.

[0032] The color pattern can be generated in various ways. According to a preferred embodiment of the present invention, the color pattern is generated using three laser diodes and at least one diffractive optical element. According to another embodiment, for example, three laser diodes located in the proximal section of the handpiece of the device according to the present invention are connected to the diffractive optical element via optical fibers. The diffractive optical element (DOE) is preferably located in the distal section of the handpiece or in the headpiece of the device and is positioned in the patient's oral cavity during the scan. The diffractive optical element preferably has three areas, ensuring that red, green, and blue stripes are projected onto the teeth.

[0033] According to a second variant of the invention, the color pattern or color stripe pattern is generated by colored LEDs (preferably red, green, blue) and apertures. In this design, the light emitting elements (here LEDs) are also preferably located in the handpiece of the device and connected via optical fibers to an aperture assembly located in the distal section of the headpiece of the device.

[0034] To avoid motion blur in the image, the projected pattern is displayed in flashes for 1 ms, which requires a high pulsed light output for the light source, in the range of 300 mW, without considering losses due to filters or coupling into optical fibers.

[0035] According to the invention, a color pattern is projected onto the surface to be captured at intermittent intervals, and images of at least one image group are captured during this projection time.

[0036] In addition to the intermittent projection of the color patterns, a white LED light is preferably provided to illuminate the surface to be scanned, which improves its visibility to the human eye and / or to a camera for recording and on-screen playback, and facilitates positioning and movement of the distal section of the intraoral scanner handpiece inside the patient's mouth during the scanning process.

[0037] The light from the white LEDs, or more precisely, the light reflected by the tooth surface, can also be used to determine the color of the tooth, more precisely the surface of the scanned object, and to roughly determine the scanned material, such as teeth, gums, or metal. For this purpose, images can be taken with one of the cameras while the surface of the scanned object is illuminated with the white LEDs and transferred to a data processor. The data processor preferably textures the 3D model generated based on this data. Similarly, according to another embodiment, color and / or material information can also be stored in the 3D model. According to further embodiments of the present invention, the color and / or material information can be used to optimize stereo matching, adjust the intensity of the structured light, and / or adapt the projection pattern to the material or color during runtime. In this context, the scanner can comprise or be connected to a control unit designed to perform these steps.

[0038] Storing color and material information in the 3D model makes it possible to segment teeth and identify interfering data such as gums, palate, braces, metal implants, or cheek or tongue during the scanning process.

[0039] All of this information can be used to estimate the accuracy of the scanning process and provide information about poor scan quality to the user or show it on the 3D display.

[0040] The scanning device according to the invention preferably comprises an acceleration sensor. If the detected acceleration or movement exceeds a predetermined threshold, according to one embodiment the scanning process is interrupted or terminated. This means that the scanning process is interrupted if the movement is too large and can be continued again if the movement is more gentle.

[0041] According to a further embodiment of the method and device according to the invention, the movement changes detected by the acceleration sensor are compared by the processor with predetermined movement change data stored in the memory unit, thereby enabling the device to be controlled by gestures made by the user.

[0042] In contrast to triangulation methods, the method according to the invention does not in principle require periodic calibration: only a factory calibration of the camera optics is provided.

[0043] A scanning device according to the invention is proposed for producing a three-dimensional image, in particular of a patient's teeth, using the method described above.

[0044] A scanning device according to the present invention comprises a handpiece having a proximal section and a distal section for insertion into a patient's oral cavity, and additionally comprises a data processor and a control unit.

[0045] The handpiece is connected to a control unit and a data processor for the exchange of information. The control unit and / or the data processor may also be located in the handpiece. According to one embodiment, the handpiece is connected to the control unit and / or the data processor by a cable. However, according to further embodiments, a system for wireless transmission of information between the handpiece and the data processor and / or the control unit may also be provided.

[0046] The distal section of the handpiece has at least two, and typically three, cameras that are used to perform the scan. The three cameras are arranged in one plane. However, in addition to embodiments with three cameras, embodiments with four or more cameras are also possible.

[0047] A system for generating the color stripe pattern, or at least components thereof, is also located in the distal section. Preferably, the color stripe pattern is generated by a diffractive optical element (DOE) in conjunction with at least three laser diodes. Preferably, the at least three laser diodes are located in the proximal section of the hand piece and connected via optical fibers to the DOE on the distal section of the hand piece.

[0048] The DOE preferably has three different areas such that each of the three laser diodes is optically coupled to a different area of ​​the DOE. Preferably, the three laser diodes are red, green, and blue.

[0049] According to a particularly preferred embodiment, the DOE is designed to project red, green, and blue color stripes having widths of 700 to 1800 micrometers at a distance of 5 to 15 mm onto the surface of the object to be scanned, in particular onto the teeth.

[0050] According to an alternative embodiment, a color pattern or a color stripe pattern shall be generated using at least three colored LEDs (red, green, and blue) and an aperture. According to one embodiment, the use of a light guide is also provided to save space and prevent heat problems. For example, a stripe or triangular pattern or tapered stripes can be generated by the aperture. Surprisingly, it was found that by using an aperture that tapers in cross section (from the light inlet to the light outlet), the light intensity within the projected stripe or within the projected triangle is optimized to the extent that a triangular intensity profile is created instead of the trapezoidal intensity profile that would otherwise be typical of an aperture.

[0051] The control unit of the scanning device is designed to control the camera located in the distal section to simultaneously take a series of photographs during the scanning process and transfer them to a data processor, which is designed according to the invention to analyze the recorded images using a stereo matching method, which allows the generation of a depth map of the image, which is converted into a 3D model by the device's data processor or by an external data processor.

[0052] The essence of the invention is that a DOE together with a laser diode or an LED together with an aperture creates a pattern with continuous intensity transitions. The pattern can be implemented by color stripes, triangular patterns, or a combination of white light and color elements such as lines or stripes.

[0053] The data processor is designed to recognize matching patterns in image pairs using color space variations.

[0054] Additionally, the surface to be scanned is illuminated by white LEDs offset to the intermittent projection of a color stripe pattern, as described above.

[0055] According to one embodiment, the scanning device in the handpiece has a rotary vibration mechanism designed to operate a DOE placed in the distal section. The color stripes generated by the DOE and projected onto the surface of the object to be scanned are blurred as a result, which corresponds to generating continuous intensity transitions of the color stripe pattern. The intensity transitions are preferably sinusoidal or approximately sinusoidal. Another important effect here is the reduction of any kind of speckle that occurs when using a laser.

[0056] In addition to the option of oscillating around one axis, it is also possible to oscillate around two axes. This makes it possible to create patterns with or without a DOE. Without a DOE, i.e., with only the laser spot, it is possible to create straight lines or Lissajous figures. With a DOE, several stripes and Lissajous figures can be created. The amplitude and frequency of the oscillations can be adjusted during the scanning process, and in particular the pattern and its width can be adapted to the material being scanned. Material detection is possible with intermittent white illumination.

[0057] The vibration mechanism can also be formed in the form of a prism or mirror with a 90° deflection.

[0058] In both embodiments, the laser diode or LED operates with a pulse length between 0.1 and 2.5 ms. A pulse length of approximately 1 ms is particularly preferred. This time is sufficient to capture at least one image group, i.e., three simultaneously recorded images. A short illumination time reduces blurring caused by movement and also allows the use of rolling-shutter camera sensors.

[0059] Due to their size, rolling shutter sensors are well suited for use in cameras in scanning devices.

[0060] According to a further variant of the invention, it is envisaged that the control unit is designed to vary the light intensity of the laser diode or LED during the scanning process.

[0061] According to a further embodiment of the invention, the control unit is adapted to adjust the light intensity of the laser diodes or LEDs depending on the intensity values ​​of the colors captured by the at least one camera.

[0062] One advantage of the scanning device according to the invention is its short scanning distance. To further reduce this distance, according to one embodiment of the invention, a prism is provided which is arranged in front of the camera in the optical direction.

[0063] Another advantage of the present invention is that when using at least three cameras, especially when the scanning process is performed over the inner and outer edges of the teeth, the distal section of the handpiece only needs to be guided once over the outer edge of the teeth and once over the inner edge of the teeth (for the upper and lower jaws respectively).

[0064] To enable the distal section of the handpiece to be guided over the tooth edge, in one embodiment of the present invention, "wings" are provided on the sides of the camera of the scanning device as guiding aids. The wings are designed and positioned so that when the distal section is guided over the tooth edge, the edge can be placed between the wings. In this case, the inside of the wings contacts either the front and top or the back and top of the tooth (especially molars). The wings are therefore designed to rest against the mentioned sides and enable scanning over the edge. In the context of the present invention, the term "scanning over the edge" means that the distal section of the scanning device is moved along the front edge of the tooth and then along the back edge of the tooth.

[0065] To this end, the wings are preferably spaced between 1 mm and 2 mm apart and preferably extend at an angle of about 35 degrees relative to the surface on which the camera is placed. The wings preferably have a height of between 2 and 4 mm.

[0066] To prevent fogging of the camera optics and other optically active components on the distal section of the scanning device's headpiece, the handpiece or distal section of the headpiece preferably includes a heating element and temperature sensor. The heating element, along with the temperature sensor and control unit, ensures that the optically functional components remain above 32°C. This helps prevent fogging of the exterior surfaces of these components. Maintaining a constant temperature for the camera and optics also improves measurement accuracy.

[0067] After scanning in the patient's mouth, at least the distal section of the scanning device handpiece must be autoclaved and is designed accordingly. However, according to particularly efficient embodiments, the scanning device may also have a snap-on protective cover that can be disposed of or separately autoclaved after each use of the device.

[0068] Alternatively, the distal portion of the handpiece can be designed to be attachable to the proximal portion of the handpiece and can be autoclaved as a whole.

[0069] According to further embodiments, the device may have a long-distance recording mode in addition to the close-range scanning function, which allows it to also perform intraoral overview scans of the dental arches or recordings of the face or facial areas outside the oral cavity.

[0070] The present invention is explained in more detail in the following drawings, which illustrate preferred embodiments only and are not to be construed as limiting. [Brief explanation of the drawings]

[0071] [Figure 1]FIG. 1 is a schematic diagram of an intraoral scanner in one embodiment with a diffractive optical element and a laser diode. [Figure 2] FIG. 1 is a diagram of an intraoral scanner with an LED and an aperture. [Figure 3a] FIG. 1 shows a configuration of a scanner head having a light guide, a DOE, and three cameras. [Figure 3b] FIG. 1 shows a configuration of a scanner head having a light guide, a deflection element, a diaphragm body, and three cameras. [Figure 3c] FIG. 10 is a cross-sectional view of an aperture body according to one embodiment. [Figure 4] FIG. 1 illustrates the use of an intraoral scanner on a tooth surface. [Figure 5a] FIG. 1 shows a preferred projection pattern projected onto a flat white surface. [Figure 5b] FIG. 1 shows a preferred projection pattern projected onto a flat white surface. [Figure 5c] 5b shows the intensity curve of the image line recorded by the camera when using the projection pattern according to FIG. 5b. [Figure 5d] 5b shows the intensity curve of the image line recorded by the camera when using the projection pattern according to FIG. 5b. [Figure 6] FIG. 10 shows a group of images with a pattern projected onto a tooth. [Figure 7] FIG. 1 shows the color gradient of line 50 (line 50) in the left and center images with red, green, and blue intensities. [Figure 8] FIG. 1 shows the recorded disparities of the left and center cameras, and the center and right cameras, as well as a composite disparity map shown in the center.

[0072] (The explanation of the symbols in this position has been moved to the end of the specification.) DETAILED DESCRIPTION OF THE INVENTION

[0073] Figure 1 shows one embodiment of an intraoral scanner according to the present invention. The intraoral scanner is divided into a handpiece 30, a neckpiece 20, and a scanner head 10. In this design, a power controller 31 is located within the handpiece 30, which provides power to a laser diode 32b, also located within the handpiece 30, which generates pulsed light having a pulse length of approximately 1 ms. The laser diode 32b is connected to an optical waveguide (optical fiber) 21 via a coupler 33, which extends through the scanner's neckpiece 20.

[0074] The optical fiber 21 is optically coupled via a focusing element, i.e., lens 17, and a 90° deflecting element in the form of a prism 12 to a diffractive optical element 16, which is housed within the scanner head 10. The lens is preferably a GRIN lens. The diffractive optical element has three areas (RGB) and ultimately generates a color pattern for projection onto the patient's teeth. The camera of the intraoral scanner is not shown in this view.

[0075] Figure 2 shows an embodiment of an intraoral scanner that has at least three colored LEDs (red, green, and blue) instead of laser diodes. Similar to Figure 1, a pulse of current of approximately 1 ms is passed through these LEDs to generate a corresponding flash of light. In this design, LED 32a is also located in handpiece 30 and optically connected to optical fiber 21 located in neckpiece 20. There is one optical fiber per aperture.

[0076] The aperture is placed in aperture body 19 as shown in Figure 3c. Finally, during the light pulse, up to 100mW of power per color emerges from projection 15. The intraoral scanner's camera is not shown in this figure.

[0077] FIG. 3a shows a scanner head 10 with three cameras 13. A focusing cylindrical lens 17 is attached to optical fibers 21 (one optical fiber for each color). This sends the laser beam through a prism 12 to a diffractive optical element (DOE) 16. A color pattern is formed in the DOE 16 and projected onto the surface to be scanned, in this case a patient's tooth 40. The light reflected by the tooth is then captured by the three cameras 13. The resulting signals are then passed, in whole or at least in part, to a data processor to determine the disparity of the individual pixels.

[0078] FIG. 3b shows components within the scanner head 10 according to another embodiment of an intraoral scanner with LEDs. The version with LEDs includes two aperture bodies 19 in which a plurality of apertures 14 (passage openings) are arranged. The apertures 14, i.e., passage openings, preferably have a rectangular, trapezoidal, or triangular cross-sectional area. Color patterns, particularly color stripe patterns or triangular patterns, can be particularly advantageously formed using two aperture bodies. In the case of a color stripe pattern, the corresponding apertures 14 of the two aperture bodies 19 are shown aligned with each other, thus forming continuous lines, or, in the case of a triangular pattern, are shown offset relative to each other. Each aperture 14 is connected to a preferably red, blue, or green LED via an optical fiber 21 (not shown here for clarity).

[0079] The use of at least two aperture bodies 19 containing multiple apertures 14 that together generate projections is particularly advantageous for intraoral scanners as it allows for a small geometric size of the scanner head 10 .

[0080] The light emitted by the aperture and, in the case of a treatment, reflected by the teeth is captured by three cameras 13 .

[0081] 3c shows a cross section of the aperture body 19 in the plane of the aperture 14. Surprisingly, it has been found that a particularly advantageous continuous intensity distribution of the projection can be achieved when the aperture undergoes a cross-sectional reduction starting from the entrance aperture 22 in the direction toward the exit aperture 23, i.e., when the cross section of the passage opening is tapered. This results in a favorable triangular intensity distribution. This triangular intensity distribution has much better optical properties for performing scanning than apertures previously known or used in the field, which means that such apertures can be considered an independently inventive aspect, particularly in connection with intraoral scanners or other preferably medical applications in which the smallest possible dimensions need to be achieved.

[0082] FIG. 4 shows an intraoral scanner being used on a dental model 40. In this view, it is clear that the scanner is being used to scan over the edges of the teeth. To guide the scanner accordingly, the scanner head has two wings 18 that laterally limit the plane of the camera. During scanning, one edge of the tooth, i.e., the inner or outer edge of the tooth, is positioned between the wings 18. The wings are preferably spaced between 1 and 2 mm apart and at a 35 degree angle to the plane of the camera.

[0083] Figure 5a shows a projection 15 of a stripe pattern on a white background. According to the embodiment shown, the projection 15 has red, green, and blue color stripes 111, 112, 113. The projection distance is preferably between 5 and 15 mm. The stripes are preferably formed by corresponding aligned apertures 14 in two aperture bodies 19.

[0084] Figure 5b shows the projection 15 of a triangular pattern on a white background. The preferred projection distance is between 5 and 15 mm. This variant is produced using LEDs and corresponding apertures 14, which have a triangular cross section and are arranged on two aperture bodies 19, laterally offset from each other by half the width of the base of the triangle.

[0085] Overall, this offset triangular projection allows for more color transitions with fewer light sources than stripe projection, where stripes are created by two corresponding aligned apertures 14 on two aperture bodies 19. Compared to stripes, color changes also occur laterally, i.e., from the base to the tip of the triangle.

[0086] Figure 5c shows the intensity profile of the central row of the central camera image 52 (at optimal aperture) when the triangular color pattern of Figure 5b is projected onto a white background. The aperture or light source used to create the triangle is placed at the widest part of the triangle with respect to the distance to the center of the camera (see aperture configuration in Figure 3b). Therefore, the intensity decreases significantly towards the tip as the distance increases.

[0087] Figure 5d shows the intensity curve of the line below the center camera image 52 (at optimal aperture) when the triangular color pattern of Figure 5b is projected onto a white background. Compared to Figure 5c, the intensity peaks are smaller due to the greater distance to the aperture. The difference in intensity peaks can be reduced by optimizing the aperture. Ideally, the peaks should have the same intensity.

[0088] Figure 6 shows three camera images 51, 52 and 53 in which the projection according to Figure 5a was recorded on the surface of the tooth model 40. The individual color stripes red 111, green 112 and blue 113 are further smoothed by the optical properties of the tooth and therefore blend together. Due to the uneven surface of the tooth, the individual stripes in the projection are no longer simply parallel to each other. The straight line 50 represents the camera line that is analyzed in Figure 7 with respect to the color gradient.

[0089] Figure 7 shows the intensity profiles of the individual colors along the camera line 50 of Figure 6 for two cameras. This shows that the color stripes 111, 112, and 113 create minima and maxima at the camera line 50. Comparing the intensities of the individual colors, similar curves and corresponding points (maxima 211, 212, 213) or intersections (214, 215, 216) are seen. Further values ​​in between can also be assigned. Thus, the displacement (disparity) of individual image pixels within the line can be determined point by point. Stereo matching algorithms are more complex but are based on this assignment. They analyze not only point by point, but also the entire area.

[0090] Figure 8 shows three disparity maps: one from the left camera to the center camera (left map), one from the center to the right camera (right map), and one combined disparity map (center map). Disparity was calculated in each case relative to the center camera. From this disparity, depth can be determined. Dark dots indicate that the disparity cannot be determined, or cannot be determined with sufficient accuracy. Light values ​​indicate high disparity or proximity to the camera. Since disparity can only be determined for the area that the corresponding camera can "see," the left disparity map is restricted to the right side and the right one to the left side.

[0091] The two disparity maps have an overlapping area where two disparity values ​​can be obtained for each image pixel, which allows the computation of a center map, which shows the more accurate disparity or depth values ​​within the overlapping area. [Explanation of symbols]

[0092] In Figure 5b, Mitte: means "middle" and Unten: means "bottom." [Explanation of symbols] 10 Scanner Head 12 Deflecting element with prism or mirror 13 Camera 14 Aperture 15 Projection 16 Diffractive optical elements 17 Focusing element / lens 18 Wing / Guidance 19 Opening body 20 Neckpiece 21 Light Guide 22 Entrance aperture 23 Exit aperture 30 handpieces 31 Power Controller 32a LED 32b laser diode 33 Coupling to light guide 40 tooth surfaces / model 50 Camera Line 51 Left camera image 52 Central camera image 53 Right camera image 111 Color Filter Stripe Red 112 Color Filter Stripe Green 113 Color Filter Stripe Blue 121 Color Intensity Red 122 Color Intensity Green 123 color intensity blue 211 Maximum value red 212 Maximum value green 213 Maximum value blue 214 Equal Intensity Red / Green 215 Equal Intensity Red / Blue 216 Equal Intensity Green / Blue

Claims

1. 1. A method for producing a three-dimensional image using a scanning device, comprising: projecting a color pattern (111, 112, 113) onto a surface (40) to be captured; Recording a plurality of images using at least three cameras (13) spaced apart and arranged in a plane, said plurality of images comprising a plurality of image groups, each of said image groups comprising images taken simultaneously using said at least three cameras (13), and transferring said plurality of images to a data processor; comparing at least two of the images (image pairs) taken simultaneously by the at least three cameras (13); detecting corresponding patterns in the image pair, each corresponding to the same local area of ​​the surface (40) of interest; calculating the displacement of individual image pixels of the corresponding patterns or of image pixels of the image pair; generating at least one depth map having depth information from at least one image pair; combining the depth maps generated from the images of the group of images; Equipped with 1. A method in which the color patterns (111, 112, 113) projected onto a surface (40) and detected by the camera (13) produce predominantly continuous intensity profiles in the individual color channels, and matching pixels or patterns in the image pair are detected by comparing the direction and length of color vectors in color space, A method, characterized in that the color pattern (111, 112, 113) is projected intermittently onto the surface (40) to be detected, and images of at least one image group are detected within a projection period.

2. 2. The method of claim 1, wherein a white LED intermittently illuminates the surface (40) to be detected, offset relative to the projection of the color pattern (111, 112, 113).

3. 3. The method of claim 2, wherein reflections of light emitted by the white LED are captured and used to determine the color and / or material of the surface (40) of the scanned object.

4. 3. The method of claim 2, wherein reflections of light emitted by the white LED are captured and further used to create a depth map.

5. 2. A method according to claim 1, characterized in that at least two image pairs are formed in each image group and are checked in each case for a corresponding pattern.

6. 2. The method of claim 1, wherein the depth information from at least two image pairs of an image group is compared with each other to achieve higher information quality and reliability.

7. 2. The method of claim 1, wherein the color pattern is generated by three laser diodes (32b) and at least one diffractive optical element (16) or by a colored LED (32a) and a (tapered) aperture.

8. The scanning process is interrupted if the detected movement of the camera (13) exceeds a predetermined threshold; 2. The method of claim 1, characterized in that the method is automatically resumed if the movement of the camera (13) detected by an acceleration sensor is below a predetermined threshold.

9. 2. A method according to claim 1, characterized in that the scanning method is controlled by comparing the recorded acceleration patterns with acceleration patterns stored in a memory (gestures).

10. 10. The method according to any one of claims 1 to 9, characterized in that, in contrast to triangulation methods, no calibration is required before or during the scanning.

11. 1. A scanning device for performing dental intraoral scans, comprising: a control unit, i.e. a data processor, located in the handpiece (30) of the intraoral scanner; a handpiece (30) connected to said data processor for exchanging information, said handpiece having a distal section (10) intended to be inserted into the oral cavity of a patient; Equipped with At least three cameras (13) arranged in a plane, and at least one diffractive optical element (16) or at least one aperture (14) are arranged in the distal section; the diffractive optical element (16) together with at least one laser diode (32b) or the aperture (14) together with at least three LEDs (32a) are designed to project a color pattern (111, 112, 113) onto the surface (40) of the object to be scanned during a scanning process; 1. A scanning device, wherein the data processor is configured to generate a depth map using images recorded during the scanning process by applying a stereo matching method and to transfer them to a procedure for creating the depth map, 1. A scanning device, characterized in that the color patterns (111, 112, 113) projected onto a surface (40) and detected by the camera (13) produce predominantly continuous intensity profiles in the individual color channels, and the data processor is designed to recognize matching patterns in image pairs using variations in color space.

12. 12. The scanning device of claim 11, wherein a diffractive optical element (16) having three regions is optically connected via optical fibers to three laser diodes (32b) (red, green, blue) located in a proximal portion of the handpiece (30) to generate the color patterns (111, 112, 113).

13. 12. The scanning device of claim 11, wherein a vibration mechanism is provided to generate continuous intensity transitions of the color pattern (111, 112, 113), the mechanism vibrating the diffractive optical element or 90° deflection element (MEMS-based micromirror), thereby "blurring" the color pattern and reducing speckle.

14. 12. Scanning device according to claim 11, characterized in that a laser beam is coupled directly into the diffractive optical element (16) without an optical fiber (21).

15. 12. The scanning device of claim 11, wherein each of the LEDs for each color is connected to at least one aperture (14) via an optical fiber.

16. 12. A scanning device according to claim 11, characterized in that "wings" are arranged on the scanner head (10) of the scanning device transversely to the camera (13) of the scanning device as guiding aids (18), thereby enabling the scanner head (10) to be guided along the inner and outer edges of the molars.

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