EP-4504095-B1 - INTRAORAL SCANNING DEVICE WITH EXTENDED FIELD OF VIEW

EP4504095B1EP 4504095 B1EP4504095 B1EP 4504095B1EP-4504095-B1

Inventors

KjÆr, Rasmus
ÖJELUND, Henrik

Dates

Publication Date: 20260513
Application Date: 20230405

Claims (20)

An intraoral scanning device (1) for scanning a dental object (2), comprising: - an elongated probe (3) defining a longitudinal axis (4) of the scanning device (1); - a first scan unit (14) comprising: - a first projector unit configured to project a light pattern (7) onto a surface of the dental object (2), wherein the first projector unit defines a first projector optical axis; - at least one camera (9) comprising an image sensor (10) for acquiring images, wherein the at least one camera (9) defines a camera optical axis (11); and - a reflecting element (12) configured to reflect light from the first projector unit and/or reflect light from the surface of the dental object (2) and onto the image sensor(s) (10) of each camera (9); - a second scan unit (16) comprising: - a second projector unit configured to project a light pattern (7) onto a surface of the dental object (2), wherein the second projector unit defines a second projector optical axis; and - at least one camera comprising an image sensor for acquiring images, wherein the at least one camera defines a camera optical axis; wherein each scan unit (14; 16) defines a field of view (FOV), characterized in that the projector optical axis and the camera optical axis of each scan unit define a camera-projector angle of between 5° to 10°.
The scanning device according to claim 1, wherein the projector unit is configured to project unpolarized white light.
The scanning device according to any of the preceding claims, wherein the light pattern is static in time.
The scanning device according to any of the preceding claims, wherein the scanning device comprises an optical window made of a polymer or glass, wherein the optical window is located in a distal end of the elongated probe.
The scanning device according to any of the preceding claims, wherein the first and second scan units are arranged to project the light pattern through the optical window.
The scanning device according to any of the preceding claims, wherein the second scan unit further comprises a reflecting element configured to reflect light from the second projector unit and/or reflect light from the surface of the dental object and onto the image sensor(s) of each camera of the second scan unit.
The scanning device according to any of the preceding claims, wherein the scan units are positioned along the longitudinal axis of the scanning device.
The scanning device according to any of the preceding claims, wherein the first and second projector optical axes are substantially parallel.
The scanning device according to any of the preceding claims, wherein a minimum bounding box of a first scan unit overlaps a minimum bounding box of a second scan unit.
The scanning device according to any of the preceding claims, wherein the first and second scan unit are configured to project the light pattern on the same side of the scanning device.
The scanning device according to any of the preceding claims, wherein each scan unit comprises two or more cameras, wherein said cameras are configured to acquire a set of images.
The scanning device according to claim 11, wherein the number of images in the set of images corresponds to the number of cameras in a given scan unit.
The scanning device according to any of the claims 11-12, wherein the cameras are synchronized such that images within the set of images are acquired simultaneously.
The scanning device according to any of the preceding claims, wherein each scan unit comprises four cameras.
The scanning device according to any of the preceding claims, wherein each scan unit comprises one projector unit and a plurality of cameras, wherein the cameras are arranged on two axes to form a cross in the plane, wherein the projector unit is located in the center of the cross when viewed along the projector optical axis, wherein the two axes are substantially parallel with at least two edges of the reflecting element.
The scanning device according to any of the preceding claims, wherein each scan unit defines an angular field of view (AFOV) of between 60° to 75°.
The scanning device according to any of the preceding claims, wherein for a given scan unit, the center-to-center distance between the projector unit and a given camera of that scan unit is between 2 to 5 mm, preferably between 3 to 4 mm.
The scanning device according to any of the preceding claims, wherein the field of view of each scan unit is at least 400 mm 2 at a working distance of between 15 mm and 50 mm.
The scanning device according to any of the preceding claims, wherein the scanning device employs a triangulation-based scanning principle.
The scanning device according to any of the preceding claims, wherein the scanning device comprises one or more processors configured for generating a three-dimensional (3D) representation of the dental object.

Description

Technical field The present disclosure relates to an intraoral scanning device for scanning a dental object. The disclosure further relates to a dental scanning system for acquiring images of the object and for generating a digital representation of the object. In particular, the present disclosure relates to an intraoral scanning device comprising a plurality of scan units. Background Digital dentistry is increasingly popular and offers several advantages over non-digital techniques. Digital dental scanning systems typically utilize a scanning device, such as an intraoral 3D scanner, to generate a three-dimensional digital representation of an intraoral three-dimensional object/surface of a subject. A variety of different technologies exist within scanning devices, such as triangulation-based scanning, confocal scanning, focus scanning, x-ray scanning, and stereo vision. Optical scanning devices often feature a projector unit for projecting an illumination pattern onto the surface of a 3D object, and an image sensor for acquiring one or more images of the illuminated object. For triangulation-based scanning devices, the projector unit and the camera are offset such that they form a triangle with a given point on the surface of the illuminated object. In general, a scanning device is associated with a field of view (FOV). The FOV can be understood as the extent of the observable world that is seen at any given moment by the scanning device. Typically, the FOV is reported as an area measure at a given distance from the projector or camera, or the area can be measured a given distance below a tip of the scanning device. Within digital dentistry, a full digital impression of a patient's teeth is typically obtained. Thus, during a scanning session, the dentist maneuvers the tip of the scanning device across the patient's dental arches until images of all the teeth are obtained. In some cases, only parts of the patient's dentition are imaged using the scanning device. However, in general it is desired that the digital impression is obtained fast and that the scanning is pleasant for the patient. Since the FOV determines how much of the teeth can be scanned by the scanning device at a given moment, the FOV consequently influences the time it takes to complete a scan. It is generally desired to have a large FOV, thus covering a large area, since it allows for more data/images to be captured at any given moment, and thus enables a faster scan. Furthermore, a large FOV enables a larger overlap of the acquired data, which enables a more accurate and reliable generation of the digital 3D representation of the patient's teeth. In some cases, it can be difficult to image the patient's dentition if one or more teeth are missing. Hence, in such cases it is beneficial to have a scanning device with a large FOV, since it enables capturing images of the neighboring teeth across a missing tooth. In addition to a large FOV, it is generally desired that the tip of the scanning device that enters the patient's mouth during the scanning session is rather compact or small, since large scanning tips can be unpleasant to the patient. Furthermore, if the tip of the scanning device is too large, such as if the tip height is too large, it can be difficult to reach all relevant areas inside the oral cavity of the patient. Therefore, it is desired to have a small tip height of the scanning device. It is therefore of interest to provide a scanning device with a reduced tip height and a large field of view. A challenge associated herewith is that typically the field of view scales with the tip height. As an example, a scanning device having a very small tip, e.g. for use on a child, will generally have a smaller FOV compared to a regular sized tip, e.g. configured for adults. Therefore, it remains a challenge how to increase the FOV while keeping the tip height of the scanning device minimal. US 2020/205942 A1 discloses a method of scanning an oral cavity including: acquiring, using an intraoral scanner (IOS) head, without changing a position of the IOS head, a first image of a first region of interest (ROI) and a second image of a second ROI where the first and the second ROIs are of different portions of a dental arch of the oral cavity and do not overlap; reconstructing depth information for the first and the second ROI; and generating a single model of the dental arch by combing the depth information. Summary The invention is as defined in the appended claims. There are further challenges with the above objective of providing a scanning device with a large field of view. In general, providing a large field of view using close-focus optics, i.e. optics with a high focusing power or short focal length, results in a large variation in magnification and illumination in the projected light / acquired images. Furthermore, it can result in a large angle of incidence of the projected light with a front window in the tip of the scanning device,