Optical impression tray device

Abstract

Title: Optical impression taking device The invention relates to an optical impression taking device capable of taking pictures for the three-dimensional reconstruction of a dental object representing at least a part of at least one dental arch and comprising, in a support piece of the dental impression holder type adapted to cover at least partially the dental object, an optical assembly having: a light emission system comprising light sources (3') to illuminate the dental object;optical modules (1) with light measurement sensors distributed in a back wall (4) of the support piece oriented, during image capture, towards the dental object, said optical modules (1) being capable of capturing direct light radiation emitted by the light emission system, and indirect light coming from the optical assembly and the dental object. In addition, it includes means of protection (2) for the optical modules (1), said means of protection (2) allowing the passage of light rays. Figure for the abbreviation: Fig. 1;

Description

Title of the invention: Optical impression holder device

[0001] The present invention relates to an optical impression tray device usable for taking three-dimensional and temporal impressions in dentistry. This device is of the same type as traditional impression trays operating with molding materials, but includes optoelectronic imaging systems using light sources and optical measurement sensors to digitize at least a portion of a dental arch. Such a device must then be connectable, by cable or wirelessly, to a hardware and software system first for transmitting the information collected by said sensors, and then capable of sequencing and / or storing, processing, and / or displaying this information to enable the taking of an optical impression in one or more captures.The field of application of the devices of the invention also implies particular constraints, for example, protective hermeticity of the electro-optics due to the existence of mandatory disinfection products in the medical field.

[0002] The present invention is intended to facilitate and optimize the capture of at least one three-dimensional view of all or part of a dental arch, either in the mouth or on a reproduction model. One of the objectives is to simplify the positioning of the device so as to maintain it in the ideal focal zone to ensure good image capture without hindering any movements necessary for correct three-dimensional reconstruction. One of the difficulties lies in the fact that the captured 3D surface information may contain blind spots resulting in particular from stray reflections and light artifacts that can be caused by illumination from light sources in the dark environment of the mouth.

[0003] The device of the invention must in practice limit these blind spots by significantly reducing light reflections on the different locations / walls of the device which are in the path of the light rays, but which also appear on the surfaces of the teeth, gums or bone, while preserving the conditions for good disinfection of its surfaces.

[0004] For 50 years, one of the inventors of the present application has proposed several devices or methods using optical or ultrasonic measurements in a patient's mouth as a means of making diagnoses, for example in the clinical study of orthodontic movements using brackets or aligners, or for designing and manufacturing dental prostheses and implants by combining a computer with a numerically controlled machine tool. Work has also been carried out to the creation of remote prostheses based on data resulting from digitized dental objects. The corresponding inventions have been the subject of patents such as documents referenced EP 0040165 and EP 0091876, relating to taking impressions by optical means and, more recently, documents WO2011 / 154656 and WO 2019 / 145658 which also relate to an optical impression tray.

[0005] If these documents do indeed correspond to the needs of modern dentistry, in particular what is described in the latter cited, it turns out that in practice, the implementation of these inventions has required additional research to facilitate their exploitation, which is in particular the subject of the present application.

[0006] We also know of numerous documents in which solutions are proposed to problems relating to the same overall objective of digitizing optical data.

[0007] This is the case, for example, with US patent 2017100219 A1, which describes an impression tray comprising assembleable and detachable elements consisting, among other things, of sensors capable of taking an impression of a tooth or an arch, these electro-optical means being associated with a traditional molding material. US patent 2015118638 A1 also discloses an impression tray, in this case consisting of a tray and a channel, equipped with optical sensors for obtaining images which, when combined, are intended to determine the depth of the sulcus in an edentulous patient for the purpose of fabricating their prosthesis. Such an impression tray, however, was not designed for surface image capture of the mouth.

[0008] US patent 2017128173 A1 also discloses an optical scanning device comprising a handle for operator use and a mouthpiece incorporating a movable 3D scanner. This patent describes means for moving said 3D scanner within the mouthpiece. The mouthpiece has a partially transparent casing inside which mirrors move to perform a scan to digitize the mouth. While such a device may initially appear simple to use, its application has major clinical limitations. Indeed, regardless of the movement capabilities of the 3D scanner within the mouthpiece, not all dental surfaces can be reached, and therefore cannot be measured with the same precision. Moreover, not all surfaces can be reached at all times.Furthermore, to ensure all teeth are visible, extensive adjustments are necessary, particularly depending on the size of the mouth. Finally, all devices that have attempted to use this type of mechanical movement encounter sterilization problems.

[0009] In the same vein, US patent 2002 / 064752 A1 describes a mechanically driven trolley that is very complex to operate, primarily in the mouth. This device includes a rail that follows the shape of the dental arch, on which... This device, capable of scanning the buccal and lingual surfaces of the teeth in the dental arch, is once again being introduced. In practice, it is difficult to use in the mouth due to the anatomical variations in the shapes of human jaws. US patent 2015 / 079534 Al, on the other hand, presents a well-known articulated solution for impression trays, enabling the three-dimensional reconstruction of dental arches, but which requires complex calibrations and, consequently, extensive training for practitioners: it is therefore not a user-friendly or easy-to-use tool.

[0010] However, as shown by one of the inventors of the device of the present invention, in document US 11,357,601 B2 (WO2019 / 145658), there must be virtually no movement in the optical impression tray supporting the cameras if one wants to preserve the minimum precision required in dental clinics, which must be a few tens of microns, so as not to have to recalibrate the device for each measurement and for each patient.

[0011] Most of the above-mentioned devices struggle to meet the clinician's objectives, namely to have a system covering the entire mouth and gums, without any mechanism that could malfunction during use and / or, above all, without requiring calibration for each image. While a slight movement of a few millimeters is acceptable and even desirable during the image capture to compensate for the natural and physiological movement of any patient, one of the objectives is for the device itself to be able to remain static, ensuring very rapid image capture, lasting only a few seconds. Furthermore, such a device must require very little training, be user-friendly for the dentist, and comfortable for the patient, both in its use and its size within the mouth.Finally, its cost must remain affordable for the daily use of a dental practice or laboratory, which is notably impossible in the so-called "mechanically driven" systems seen previously.

[0012] The aim of the present invention is to provide an easy-to-use optical impression tray that allows for spontaneous insertion by the dentist and provides a precision of a few tens of microns in the measurements taken. A non-traumatic shape, similar to traditional impression trays using molding materials such as those traditionally used by dentists, is employed because it has proven satisfactory for both patients and dentists, without requiring any changes to their practices.

[0013] As explained in document FR 18 50689 of the same inventor, the objectives of such devices also include collecting and measuring, simultaneously or in a very short time, the shape of the dental surfaces and their shades, but also the gingival surfaces and possibly the bone contours for surgical purposes. It may also be necessary to measure the interlocking of the maxillary teeth with the mandible in occlusion, and possibly their movements.

[0014] Given the very specific conditions of intraoral imaging, particularly in terms of lighting and humidity, numerous obstacles hinder the design and development of such a device. For example, some cameras are "dazzled" by the LED lights in front of them during the image capture. Similarly, specular reflections from these same LEDs on the surface of the teeth, which are generally white and very bright, often saturate the sensors, rendering them unable to capture certain useful information. Furthermore, cameras positioned too far from the focal plane of the image capture, which is of course located at the level of the teeth, result in a decrease in the system's accuracy. Finally, color variations within the mouth, particularly between the gums and healthy or damaged teeth, can lead to measurement errors.

[0015] The present invention aims to provide industrially acceptable, clinically usable, and cost-effective solutions to all the aforementioned problems, with the objective of achieving the previously mentioned precision on the order of a few tens of microns, regardless of the surface area of ​​the body being measured. The necessary information must be captured with a minimum of blind spots, which often correspond to specular reflections of light sources on the teeth, resulting in areas without information. The expected results are consistent diagnostic quality and good adaptation of prostheses made from the model constructed using optical impressions taken with the invention, without requiring the practitioner to perform overly complex manipulations or training.

[0016] The solutions that will be given in the following are not limited to impression trays applicable to gingival and dental surfaces, but are intended to apply to all three-dimensional imaging systems using multi-camera devices operating with artificial (LED, plasma, laser...) or natural (sun) lighting.

[0017] In fact, more precisely, the invention applies to an optical impression taking device capable of taking photographs for the three-dimensional reconstruction of a dental object representing at least a part of at least one dental arch and comprising, in a known manner, in a support piece of the dental impression tray type or fraction of a dental impression tray adapted to at least partially cover the dental object, an optical assembly having: - a light emission system comprising light sources to illuminate the dental object; - Optical modules with light measurement sensors distributed in a back wall of the support room, oriented towards the object during filming dental, the said optical modules being capable of capturing direct light radiation emitted by the light emission system, and indirect light coming from the optical assembly and the dental object.

[0018] According to the invention, this device is such that it includes means for protecting the optical modules, said means for protecting allowing the passage of light rays.

[0019] In short, the present invention comprises an impression tray including cameras and light projections, the internal arrangement of which, the object of the invention, has been designed to limit, or even eliminate, areas of light reflection and brightness on the teeth in order to allow the sensors to optimally collect the information necessary for accurate 3D reconstruction by stereoscopy in structured or unstructured light. Given the humid environment of the mouth and the presence of disinfectant chemicals, means of protecting the optoelectronic components are provided.

[0020] More specifically, what can be described as an optical impression tray within the meaning of the invention, usable for diagnosis and two-dimensional, three-dimensional, and temporal measurement in the dental and medical fields to ensure accurate capture of information in the mouth or on a plaster model or one obtained by stereolithography, consists in fact of a device comprising, within a shell (the support piece containing the optical assembly) that adapts to the shape of the object to be analyzed, a number of optical and optoelectronic components. These components are distributed in one or more planes and / or on a curved shape, whether regular or irregular, whose "field of view" covers all or part of one or more teeth, or one or two dental arches to be visualized or measured by means of one or more light sources.These can be identical or different, Lambertian and / or direct or indirect specular, the intensity and exposure time of which are automatically adjusted by software controlling the device of the invention.

[0021] Optical rays are transmitted either directly or by means of optical systems that may include fibers, diffusing materials, reflectors and / or mirrors, in combination or not. As will be seen later, the device may include LED-type sources, but also radially diffusing glass fibers, or even molded optics.

[0022] The necessary protective measures in such an environment can be of several types. Thus, according to a first variant of the device, the protective measures for the optical modules consist precisely of at least one flat, non-reflective, transparent plate intended to be placed on the dental object and to separate the back wall of the dental object from the lateral edges of said plate. joining the back wall. It must allow for a support and / or spontaneous sliding position of the assembly on the teeth and ensure the partial or total hermeticity of the opto-electronic system against external aggressions. It therefore also has a mechanical positioning function on the dental object, guaranteeing a correct focal length for the optical modules, while allowing slight movements (by sliding) to enable the acquisition of multiple images if necessary for photogrammetry.

[0023] To address the aforementioned issue concerning areas of light reflection and brightness, the transparent plate used in the invention is a non-reflective glass. It may be a transparent plate coated with an anti-reflective film on at least one side, in order to eliminate reflections as much as possible and improve the signal-to-noise ratio. The transparent plate may also be a polarizing glass.

[0024] Various configurations are possible for the light sources of the light emission system. Thus, at least some of the light sources of the light emission system can be integrated into the back wall around the optical modules. This results in direct lighting composed of sources, for example LEDs, placed around the cameras and directly illuminating the scene with or without a transparent panel. In the latter case, the protection of the electronic system is located directly at the level of and in front of the cameras and LEDs (see below).

[0025] Alternatively or in combination, at least some of the light sources may be placed in the support piece so as to emit light towards the back wall of said support, said back wall or at least a layer covering it having reflective properties. This constitutes the implementation of indirect illumination of the dental object, which may be in addition to direct illumination.

[0026] According to yet another possibility, at least some of the light sources of the light emission system can be placed in the support piece so as to emit light simultaneously towards the back wall of the support and towards the dental object, said back wall or at least a layer covering it having reflective properties.

[0027] In the latter case, indirect lighting is interesting in suppressing specular reflections, and direct lighting is useful in suppressing parasitic reflections which occur during the illumination phases of the dental object, whatever it may be (a complete dental arch, a portion of such an arch, the lateral faces of two portions of arches in contact...).

[0028] According to the invention, the light sources of the light emission system can be placed in the support next to the two lateral edges of the transparent plate.

[0029] In this case, preferably, the light sources are positioned in the plane of the transparent plate, at least along one lateral edge of said plate, opposite a reflector located on the opposite side of the transparent plate from the back wall and oriented so as to reflect the light rays simultaneously towards the dental object and towards the back wall of the support. The indirect lighting is directed towards the back wall of the support piece, and the direct lighting is actually lateral lighting of the dental object.

[0030] According to one possible configuration, the reflector has a flat reflective surface inclined relative to the transparent plate at an angle between 30° and 60°, preferably 45°. In addition, preferably, a diffusing translucent window is interposed between the reflector and the dental object: the diffuse lateral illumination it provides helps to suppress unwanted reflections.

[0031] The configuration of the device can, however, change depending on the portion of the support considered and the dental object facing it. Thus, the optical treatment of molars is not carried out in the same way as that of incisors, for example, due to the different morphology of these two types of teeth. For molars, the device of the invention exhibits a form of symmetry, and the two lateral surfaces (vestibular and lingual) of the tooth are treated, optically speaking, in essentially the same way. For an incisor, on the other hand, for one of the lateral edges of the transparent plate, at least one additional optical module and a light emission system are placed on the opposite side of the transparent plate from the back wall, and facing the dental object. These components are therefore positioned, during a shooting phase, directly lateral to one surface of the tooth, in this case the buccal surface.

[0032] In addition to the type of tooth illumination configuration as described so far, the surface finish of certain parts of the device is also a parameter to consider, since these may be diffusing bodies within the optical assembly of the invention. Thus, preferably, the back wall of the support is white. The surface grain size also plays a role in ensuring the effectiveness of the white diffusing body, particularly in preventing reflection concentrations, which are the opposite of diffusing. The reflection should be as random as possible, i.e., it should not distinguish between incident light sources. To this end, the back wall of the support preferably has a fine grain size.

[0033] In order to limit or reduce reflections, according to the invention, the device is designed such that the light spectrum of the light sources and the light spectrum of the light measurement sensors of the optical modules are between 380 nm and 550 nm, that is to say, they are practically selected to be close. This aims to improve the signal-to-noise ratio without reducing the luminous power of the light source.

[0034] According to one possible configuration, particularly suitable for devices for treating dental arches or portions thereof, the bottom wall of the support piece is, in cross-section, arched or domed. Such a curve generates a curved surface that allows the support piece to cover the teeth, and the optical beams to access their occlusal surfaces as well as their lateral surfaces, for a complete reconstruction without inaccessible areas.

[0035] According to a variant of the device of the invention, the protective means may consist of an overmolding on the back wall of the support, forming a molded optical layer covering the optical modules, said layer being reflective. There is then no longer a flat transparent plate, and the aforementioned problems related to reflections or spots of light on said plate disappear. The overmolded layer ensures sealing and consequently protects the optical modules, and it does not interfere with their operation; moreover, it becomes an integral part of them in the portion that covers them.

[0036] The specular reflections on the enamel of the teeth are also attenuated with this second variant, but the preservation of the distance between the latter and the optical modules is no longer ensured.

[0037] This is why this variant may include at least one mechanical stop against the dental object, in order to preserve as much as possible the focal distance between the observed dental object and the optical modules. The physical stop, which does not necessarily have any particular optical properties, encroaches on the dental object and results in the creation of blind spots that are detrimental to data analysis, which must then be removed during software processing: these spots are, however, easy to recognize, particularly following shifts between several captures, and therefore relatively easy to "erase" in software.

[0038] In the device of the invention, the light sources of the light emission system are chosen from among coherent or non-coherent light-emitting diodes (LEDs), optical fibers, plasma sources and halogen sources. These different types of sources can also be combined with each other.

[0039] In one possible configuration, the light emission system can consist of an array of light sources, for example, LEDs embedded in a transparent or diffusing array. Grids can also be placed in front of the light sources to create structured light. The light is then structured in the form of the projection of such a grid onto the dental object. The grid can take many forms. In this In this configuration, the light sensors are not equipped with them, in order not to reduce the intensity of the signal.

[0040] According to yet another possibility, Fresnel lenses can be placed in front of the light sources. The homogenization of the radiation resulting from the passage of the radiation through Fresnel lenses makes it possible to reduce its specularity.

[0041] The light measurement sensors of the optical modules used in the device of the present invention are, for example, of the CCD or CMOS type. Furthermore, the optical modules may include at least one static or dynamic optical system of the lens or fiber type associated with the light measurement sensors. These means allow for better control of the depth of field during the capture of optical information.

[0042] According to yet another possibility, polarizing filters can be placed in front of the light sources and in front of the light sensors, the polarizing filters placed in front of the light sensors filtering the light signal in a direction perpendicular to the filtering direction of the filters placed in front of the light sources. This solution is particularly applicable in cases of direct illumination, and when the protective measures consist of overmolding the optoelectronic components.

[0043] In summary, the device of the invention functions as an optical impression holder schematically comprising information capture cameras and light projections and whose internal arrangement, the object of the invention, has been organized to limit, or even eliminate, areas of light reflection and brightness on the teeth and on certain parts of the device in order to allow the sensors to collect as best as possible the information necessary for a good 3D reconstruction, by stereoscopy, in structured or unstructured light.

[0044] Other objects and advantages of the present invention will become apparent in the following description, relating to embodiments which are given only by way of example. Understanding this description will be facilitated in particular by reference to the figures attached hereto, for which:

[0045] [Fig.1] shows a sectional view of a first variant of the optical impression taking device of the present invention, in its portion adapted for the treatment of premolars and molars, comprising direct light sources and a transparent protective plate;

[0046] [Fig.2] represents the same sectional view of another variant with light sources direct and without a protective wall;

[0047] [Fig.3] shows said sectional view of yet another variant of the device optical impression taking of the present invention, comprising indirect light sources;

[0048] [Fig.4] illustrates a variant of the optical impression taking device of the present invention, with light sources simultaneously providing direct and indirect lighting;

[0049] [Fig.5] represents a sectional view of the portion of the same variant of the invention intended for the treatment of incisors / canines;

[0050] [Fig.6] illustrates a second variant in which the light sources are radial emission optical fibers; and

[0051] [Fig.7] shows yet another variant according to which the means of protection of the Optical modules with light sensors are overmolded directly in contact with the latter.

[0052] In the configurations shown, the support piece for the optoelectronic components is designed to capture images of at least a portion of a dental arch, and is therefore canal-shaped so that the optical rays can access not only the occlusal surfaces of the teeth, but also their buccal and lingual lateral surfaces. The optical modules 1, acting as cameras or image sensors, are integrated into a back wall 4, which in this case forms—in cross-section—a dome or an arch, in which they are angularly distributed. The view is in cross-section; therefore, rows of cameras 1 must be visualized in the canal-shaped form that the support piece takes in three dimensions. Their positioning in the back wall 4, indicating their distance from the tooth to be observed, depends on their angular position, so as to adapt their focal length to said tooth appropriately.A transparent plate 2, for example made of glass, can be attached to the support piece at the lateral edges of the back wall 4. This is the case in the configuration of [Fig. 1]. It serves to position the device on the teeth and helps to control the depth of field. It also provides a seal against the external environment. Movements obtained by slight sliding of the plate 2 on the teeth are possible, which can be coupled with the triggering of the images so that several images of the dental object can be captured, allowing for improved 3D reconstruction by photogrammetry.

[0053] The plate 2 (which may be made of natural crystal such as quartz, glass, or synthetic material) is simply a mostly passive protective glass. It is also preferably treated, at least by the addition of at least one anti-reflective coating on one of its faces. The physical and chemical characteristics of the protective, positioning, and sliding plates are an important element of the device. of the invention, because said plates 2 must facilitate the use of the device while reducing unwanted reflections on the teeth, gums and palate, but also on the walls of the device itself. They must also not increase reflections on their own internal and external walls during the passage of the radiation, and in particular, be as free as possible from the effects of reflection and refraction.

[0054] Physically, these protective plates must be as rigid as possible. They must allow the practitioner to use the teeth as a support to spontaneously and intuitively position the cameras 1 and / or light sources 3' within the correct depth of field. This allows for the ideal positioning to achieve the best precision and resolution.

[0055] Chemically and to resist scratches from teeth naturally composed of hydroxyapatite crystals, but also of ceramics which can be very hard (Zircone) in prosthetic restorations, these transparent 2 protective, positioning and sliding plates are made of a very hard natural material (for example quartz, crystalline filled silica...) or synthetic, for example cast silica such as JGS1 UV quality,

[0056] To also reduce reflections on the surfaces, and to get closer to polarizing effect filters without having to use them, because they are expensive in terms of product and assembly, it is possible to use anti-reflective coatings on one or more of the surfaces of the plates 2. These coatings can be placed outside and / or inside the device, on all the walls that can be crossed by the radiation coming out of the light sources 3' towards the teeth and / or returning to the sensors 1.

[0057] These walls and treatments must resist as best as possible external physical, chemical or bacteriological aggressions, such as scratches from teeth, or thermal and plasma aggressions, or even chemical cleaning and disinfection products.

[0058] These walls may also contain a heating and / or cooling thermal system limiting the appearance of condensation inside and / or outside the device and possibly participating in the internal thermal regulation of the electronics.

[0059] In the device of the invention, the direct lighting source is composed of sources 3', for example LEDs, integrated around the cameras 1 and directly illuminating the scene. The light sources 3' induce unwanted reflections in the glass, in addition to reflections on the teeth during shots in the mouth, which can lead to unusable areas.

[0060] These "blind" areas can be made visible by a clinical manipulation by the operator consisting of slightly moving the impression tray on the teeth. The operator proceeds as follows: first, they capture the information. This reveals perfectly measurable areas and very good The information quality is excellent, especially since the position of the protective / sliding plate is not significantly altered. However, some areas lack information because the sensors are "dazzled" by reflections on the teeth and on the external and internal surfaces of the sliding walls. In a second step, the operator slightly slides the device across the teeth, which shifts the reflections and makes the previously unmeasurable areas perfectly measurable. Because these new areas are wholly or partially connected to the previously measured areas, a complete and accurate 3D reconstruction is made possible by this simple clinical procedure, eliminating the blind spots.

[0061] In this configuration of the device, in direct lighting (which can also be implemented in at least partially indirect lighting, as will be seen later), polarizing filters can also be used, for example integrated into the protective wall and which eliminate reflections on the teeth and on the transparent plate 2 used for protection, positioning and sliding.

[0062] These filters can also be placed in front of the light sources 3' and, at an angle depending on the type of polarizing filter composition, generally around 90°, in front of the data acquisition cameras 1. More precisely, the first filter placed in front of the emitted light polarizes it, while the second, placed in front of the camera 1, for example at 90° to the first, filters a large portion of the specular rays on the shiny surfaces of the teeth according to the well-known principle of Nicol prisms. Since these filters reduce the brightness of the sources, they necessitate increasing the power of the lighting system, but this also leads to a reduction in reflections on the teeth, which somewhat harmonizes the lighting and allows for a good overall measurement of the surfaces. The plate 2 located against the teeth, if it is in this configuration, then serves only for protection, positioning, and sliding.

[0063] In [Fig. 2], the device is practically identical, without the protective plate 2. The protective wall for the optoelectronic components is positioned directly at and opposite the cameras 1 and the LEDs 3'. It can cover a single sensor unit 1 or LED 3', or a group comprising one or more LEDs 3' and sensors 1. This configuration avoids reflections directly onto a sliding glass, which is not present, but requires the practitioner to hold the device in suspension. This configuration is particularly well-suited for use in prosthetic laboratories or in dedicated rooms within dental practices, especially if the use of a support arm holding the device is permitted.

[0064] It corresponds to a field of application of the device corresponding to measurements and diagnosis (orthodontics and periodontology) on supports made of plaster or various synthetic materials (additive method for example by stereolithography or subtractive for the fabrication of implant guides, orthodontic splints, or whitening trays...). Since these materials have little to no specular reflection, the problem of reflections on the measured surface is significantly reduced, simplifying and accelerating the process while increasing accuracy. The use of polarizing filters is, of course, also possible in this plate-free version.

[0065] In the configuration of [Fig. 3], the light sources 3' are indirectly illuminated. There are no longer any light sources around the cameras 1, but they are positioned opposite the back wall 4, from which their rays are reflected and redirected towards the teeth. This wall 4 therefore becomes a reflector that directs the light from the light sources 3' towards the teeth after reflection. It can be a reflective mirror (as in car headlights), in which case the reflected light will be specular and perfectly circumscribed, or it can be made of a diffusing matrix that reproduces, in a Lambertian manner, the light that has struck its density. The light sources 3' are placed around the perimeter of the support, either inside the arched back wall 4, as in the figure, or outside of it.

[0066] This configuration can lead to overexposure of certain radiation (around 60° and at grazing incidence). To limit this effect, which can lead to overemphasis of certain points used as a basis for the 3D stereoscopic reconstruction of dental surfaces, to make the cameras appear on the teeth, or to dazzle cameras close to horizontal, it is possible, in these overexposed areas, to cover the protective plate 2 with a more or less opaque mask.

[0067] It is obviously possible to combine the direct light sources 3' placed around the cameras 1, as in the first variant, with the indirect sources located at the periphery, as in [Fig. 3]. This makes it possible to reduce the highly specular appearance of the incident and reflected rays thanks to the interference resulting from the crossing of the direct and indirect radiation, and thus to reduce the reflections leading to the aforementioned blind spots.

[0068] In the configuration of [Fig. 4], light matrices 3 comprising the light sources, for example light-emitting diodes 3' LEDs, are placed on either side of the transparent plate 3, fixed in the edge areas of the support piece. They are located substantially in the same plane as the plate 2, the light sources illuminating downwards, towards reflectors 5 which direct the light on one side towards the dome 4, which must therefore be reflective, and on the other side towards the dental object through a diffusing wall or window 6. The dome 4 itself can also be a reflective mirror or made of a diffusing matrix that reproduces the light in a Lambertian manner. In this case, the surface treatments mentioned previously can be implemented: white background wall 4, fine grain size of the surface of said background wall 4, etc.

[0069] The homogeneity of the radiation from the sources 3' is significantly increased by adding a reflector 5 behind the source 3' and a diffuser 6 placed in front of the same source. The presence of the diffuser 6 in front of the light source 3' causes random emission of the radiation, increasing the Lambertian character of the light, which drastically reduces reflections on the teeth. The thicker the diffuser 6, the more pronounced this characteristic will be, thus increasing the luminous power without degrading this highly advantageous phenomenon in reducing blind spots.

[0070] The presence of the diffusing body 6 is very important in reducing the specularity of the light, but also in homogenizing it over all or part of the measured arc. The diffuser 6 is characterized by its color, but also by its surface finish, which defines the degree of random reflection of the radiation, and therefore how Lambertian any light source will be. The surface finish is thus very important if one wants to significantly reduce specularity and therefore the unmeasured blind spots in 3D stereoscopic topographic surveys. This surface finish depends on the roughness / grain size of the surface, generally obtained by sandblasting, and on the type of source used. It will not be the same, for example, with coherent laser light, which is inherently very specular, or with incoherent LED light, which is less specular but less powerful.

[0071] This diffusing body 6 can have all colors, including black. This absorbs all radiation according to the black body principle, and therefore obviously specular radiation, but it does little to erase the granularity of the few radiations that come out of it, which will be only moderately erased if the surface is in the form of a mirror, for example chromed (which ensures good reflection, but highlights surface defects too much).

[0072] Light colors, preferably white, best eliminate specularity. Combined with a good choice of roughness, always as fine as possible, these colors are best suited to three-dimensional readings in the mouth.

[0073] The reflector 5 located behind the source 3' allows, by creating an additional degree of freedom for the radiation axes, for the proportion of direct illumination striking the teeth laterally and the indirect proportion reflected off the wall 4 to reach the occlusal surfaces of the dental object to be adjusted differently depending on its location within the impression tray. Thus, the inclination or surface area is not the same in the incisal areas as in the molar areas, in order to better distinguish the profiles.

[0074] These irradiation gradients allow for efficient control of the overall illumination and its harmonization according to its position on the brow. Eliminating overexposed or underexposed areas makes it possible to adjust the overall intensity of The entire system is controlled by a much simpler electronic or human-machine interface, thus controlling overall saturation across the entire arcade. In practice, the system provides manual and / or automatic light intensity control with feedback to prevent under- or over-exposure.

[0075] The advantages of the mixed (direct + indirect) lighting configuration of the dental object are numerous, and include in particular:

[0076] - The lighting is sufficiently uniform;

[0077] - The lighting does not require the full power of the LED sources to operate correctly ;

[0078] - The specular reflections resulting from this type of lighting are acceptable;

[0079] - Reflections perceived by cameras other than those placed on the lateral ends are acceptable;

[0080] - For cameras placed on the lateral ends, the anti-reflective film(s) of the Plate 2 allows for a very significant reduction of perceived reflections;

[0081] - Furthermore, the horizontal positioning of the LED matrices makes it possible to make possible and to facilitate the industrialization of the devices of the invention, the assembly being more likely to be automated.

[0082] In this approach, the indirect lighting from wall 4 can also be modulated (as is possible with LEDs distributed on wall 4 in direct lighting, for example by adjusting the intensity at the power supply, the distribution in the geometry of the back wall 4, or the wavelength, by using a filter or by choosing the emitting material). Since this indirect lighting can be less intense than the direct lighting, this leads to a possible reduction in reflections of direct or indirect radiation that are problematic for the cameras 1, especially the most peripheral ones, those subjected to grazing radiation. Reducing this radiation obviously leads to a significant decrease in reflections on the teeth, and therefore to a reduction in blind spots.

[0083] Since the lateral and grazing illumination is direct on the lateral parts of the teeth, this leads to a significant increase in the signal-to-noise ratio (between 3 and 5), which is very favorable for detecting tooth profiles for stereoscopic reconstruction. This amplification of texture by the direct grazing light more than compensates for the decrease in intensity from the dome.

[0084] Similarly, the use of this device, by increasing grazing illumination compared to indirect illumination on surfaces with little relief, such as the buccal or lingual surfaces of teeth, produces an amplification of the bumps and hollows in the texture that is very favorable to the detection of points that rely on these relief references to correlate stereoscopic views with each other. There is an effect of projected shadows, a phenomenon widely used in electron microscopes. This phenomenon has the advantage of compensating for the indirect light coming from wall 4, which tends to "flatten" the relief, while maintaining good homogeneity in the distribution of light across the entire scene being viewed.

[0085] With reference to [Fig. 5], a slightly different configuration is implemented, adapted to portions of the dental arch including incisors and canines, the configuration of [Fig. 1] being more particularly suited to the treatment of premolars / molars. The differences concern both the illumination of the dental object and the image capture component. An optical impression device according to the invention comprises, for the entirety of a dental arch or half of a dental arch, both configurations, which makes it possible to cover all the areas necessary for a good 3D reconstruction of the dentition.

[0086] In fact, when traversing the area of ​​the arch, the teeth do not have the same implantation in the arch. This means that a camera, whether or not associated with lighting sources, which is well oriented to view the occlusal surface of a molar (i.e., which is placed at the top of wall 4) will only measure the incisal edge of the incisors if it maintains this same orientation in the anterior part of the mouth.

[0087] It is therefore necessary to provide different orientations depending on the areas of the dental arch. The device reconstructs the teeth using the principle of photogrammetry. By definition, the reconstruction is based on spatial measurement, which relies on precise points that must be viewed from at least two different directions. The more angles each point is viewed from, the more reconstructions are generated for each point, and the more precise and verifiable the 3D reconstruction. One of the features of the invention therefore lies in the orientations of the light source assemblies 3' and / or cameras 1. These orientations differ depending on the areas of the mouth, and specifically in the incisor areas, molar areas, and palate areas.

[0088] In particular, by way of example, the LEDs 3' and / or cameras 1 located at the top of the back wall 4 of the support piece for the optical impression tray of the invention are positioned in a plane close to the horizontal of the mouth (corresponding to Camper's plane, for example) in the molar area, while these same cameras 1 and / or light sources 3' are positioned at 90° to this plane in the incisor areas. Furthermore, one or more additional camera 1' and / or LED 3' assemblies may be provided in certain hard-to-reach areas, such as the frontal region, opposite the vestibular plane of the incisor, to increase the number of reference points and provide good, even illumination during measurement.

[0089] Specifically, the device in [Fig. 5] differs from that in [Fig. 4] in that, in the vicinity of a lateral edge of the glass plate 2, a camera 1' (that is (True in section, but actually a row of cameras if considered in three dimensions) is added, along with a 30-diode matrix 3'. These components are therefore located, as shown in the figure, under plate 2, and directly opposite the tooth. Almost the entire configuration remains the same, particularly at the opposite edge of plate 2, with the exception of this larger protrusion of the support piece under plate 2, which integrates the aforementioned optoelectronic components on one side.

[0090] Research and optimization of light specular suppression while maintaining sufficient power led to the development of a variant using radially diffused optical fibers on the inner and / or outer periphery of all or part of the impression tray. Thus, the variant illustrated in [Fig. 6] does not include discrete light source arrays, such as LEDs, but optical fibers 300 that illuminate radially and consequently send light radiation towards the tooth, also via a diffusing wall 6, and towards the reflective dome 4. It should be noted that this variant considerably simplifies the industrialization of the device of the invention, and therefore reduces the cost of the system, since it is sufficient to replace the LEDs or any other light sources, as well as the diffusing reflective walls 4, with one or more diffusing fibers placed at different levels of the device.

[0091] The use of multiple fibers also makes it very easy to obtain several wavelengths during the impression taking process (see below for comments on the importance of the different wavelengths). It then also becomes possible to change wavelengths during the impression taking. This allows for accurate and rapid colorimetric analysis, and also facilitates the investigation of oral and dental arch pathologies at a lower cost.

[0092] This optical fiber solution also has the advantage of significantly reducing the thermal problems common to any source of radiation such as LEDs or other halogen sources.

[0093] Finally, the variant in [Fig. 7] does not have a transparent plate 2, but an overmolding 2' which achieves the same level of protection and airtightness, but does not allow for the same level of depth-of-field control as in the previous configurations. It is actually a molded optical element 2' surrounding the cameras, conforming to the shape of the dome 4. It can serve simply as a molded optical lens, or simply as a light diffuser if it is transparent enough to allow visualization of the scene measured by the cameras, or even as a dual optical and light diffuser as in [Fig. 4].

[0094] This overmolded wall, like the transparent plate, is made of a material resistant to external physical, chemical or bacteriological aggressions or is covered with a material having these characteristics.

[0095] The importance of the type of light used has already been mentioned. In all these configurations, to attenuate reflections, it is necessary to choose both a wavelength with a spectrum close to the optimal sensitivity range of the camera 1 sensors to limit the emissive energy required by the source 3', and also a wavelength that causes the tooth to exhibit the least reflective structural behavior possible. The tooth has a chalky appearance, erasing almost all specular reflections in the low-wavelength (high-energy) 300-480 nm range, but these are not the best reading ranges for obtaining good color for accurate diagnoses. Good results are preferentially obtained with light sources, for example, pulsed LEDs, emitting in the 380-550 nm range.

[0096] In dentistry, optimizing wavelength and intensity offers the advantage of enabling very fast image acquisition (in frames per second, "fps"), which avoids blurring caused not only by operator movement but also, and especially, by the uncontrollable movements of patients. This makes it possible to increase the quality and quantity of information sought across the entire surface of the tooth, dental arches, and / or gums (including the palate).

[0097] It may be envisaged to use not just one type of wavelength zone, but several in the same impression tray, in order to be able to emit covering all or part of the spectrum, in order to be able to make diagnoses in the search for pathologies.

[0098] It is now well known that carious areas, gingival tumors, etc., exhibit particular behavior under certain types of radiation, such as UV, red, or even IR (fluorescence, phosphorescence, fading effects, etc.). For use in diagnostics in dental and medical practices, hospitals, pharmacies, and also by the general public, this set of variable wavelengths allows for the rapid study, mapping, storage, and / or transmission of a complete analysis of these pathologies. This lighting capability, specific to the device of the invention, enables manual or automated surface and / or temporal diagnostics using artificial intelligence. It also allows for the determination of tooth shades by colorimetry, using Mayer's principle at the pixel level of our sensors.

[0099] It should be noted that the configuration examples shown in the figures should not be considered exhaustive of the invention, which on the contrary includes structural variants, relating for example to the shape and positioning of the opto-electronic components, or to the nature of the light sources etc.

Claims

Demands

1. Optical impression taking device capable of taking images for the three-dimensional reconstruction of a dental object representing at least a part of at least one dental arch and comprising, in a support piece of the dental impression tray type or fraction of a dental impression tray adapted to cover at least partially the dental object, an optical assembly having: - a light emission system (3, 30, 300) comprising light sources (3') to illuminate the dental object;- optical modules (1) with light measurement sensors distributed in a back wall (4) of the support piece oriented, during image capture, towards the dental object, said optical modules (1) being capable of capturing direct light radiation emitted by the light emission system (3, 30, 300), and indirect light coming from the optical assembly and the dental object, characterized in that it comprises means of protection (2, 2') of the optical modules (1), said means of protection (2, 2') allowing on the one hand the passage of light rays, and on the other hand, by being placed on the dental object, to ensure a mechanical positioning function and guarantee a correct focal length to the optical modules.;

2. Optical impression taking device according to the preceding claim, characterized in that the means of protecting the optical modules (1) consist of at least one flat, non-reflective transparent plate (2) intended to be placed on the dental object and to separate the background wall (4) from the dental object, the lateral edges of said plate joining the background wall (4).

3. Optical impression taking device according to the preceding claim, characterized in that the transparent plate (2) is covered with an anti-reflective film on at least one of its faces.

4. Optical impression taking device according to any one of claims 2 and 3, characterized in that the transparent plate (2) is a polarizing glass.

5. An optical impression taking device according to any one of the preceding claims, characterized in that at least certain light sources (3') of the light emission system are integrated into the back wall (4) around the optical modules (1).

6. Optical impression taking device according to any one of the preceding claims, characterized in that at least some of the light sources (3') are placed in the support piece so as to emit light towards the back wall (4) of said support, said back wall (4) or at least a layer covering it having reflective properties.

7. Optical impression taking device according to any one of the preceding claims, characterized in that at least some of the light sources (3') of the light emission system (3, 30, 300) are placed in the support piece so as to emit light simultaneously towards the back wall (4) of the support and towards the dental object, said back wall (4) or at least a layer covering it having reflective properties.

8. Optical impression taking device according to the preceding claim, characterized in that the light sources (3') of the light emission system (3) are placed in the support next to the two lateral edges of the transparent plate (2).

9. Optical impression taking device according to the preceding claim, characterized in that the light sources (3') are positioned in the plane of the transparent plate (2), at least along one lateral edge of said plate (2), opposite a reflector (5) located on the opposite side of the transparent plate (2) with respect to the back wall (4) and oriented so as to reflect the light rays simultaneously towards the dental object and towards the back wall (4) of the support.

10. An optical impression taking device according to the preceding claim, characterized in that the reflector (5) has a flat reflective surface inclined relative to the transparent plate (2) at an angle between 30° and 60°, preferably 45°

11. HJ. Optical impression taking device according to any one of claims 9 and 10, characterized in that a diffusing translucent window (6) is interposed between the reflector (5) and the dental object.

12. An optical impression taking device according to any one of claims 2 to 11, characterized in that, for one of the lateral edges of the transparent plate (2), at least one optical module (1') additional and a light emission system (30, 3') are placed on the opposite side of the transparent plate (2) relative to the bottom wall (4), and opposite the dental object.

13. Optical impression taking device according to any one of the preceding claims, characterized in that the back wall (4) of the support is provided to be white in color.

14. Optical impression taking device according to any one of the preceding claims, characterized in that the bottom wall (4) of the support has a fine grain size.

15. Optical impression taking device according to any one of the preceding claims, characterized in that the light spectrum of the light sources (3') and the light spectrum of the light measurement sensors of the optical modules (1) are between 380 nm and 550 nm.

16. Optical impression taking device according to any one of the preceding claims, characterized in that the bottom wall (4) of the support piece is, in section, arch-shaped.

17. Optical impression taking device according to claim 1, characterized in that the protection means consist of an overmolding (2') on the bottom wall (4) of the support, forming a molded optical layer covering the optical modules (1), said layer being reflective.

18. Optical impression taking device according to the preceding claim, characterized in that it comprises at least one mechanical stop for support on the dental object.

19. Optical impression taking device according to any one of the preceding claims, characterized in that the light sources of the light emission system are chosen from coherent or non-coherent light-emitting diodes (3'), optical fibers (300), plasma sources and halogen sources.

20. Optical impression taking device according to any one of the preceding claims, characterized in that the light emission system consists of an array (3, 30) of light sources (3').

21. Optical impression taking device according to any one of the preceding claims, characterized in that grids are placed in front of the light sources (3') to constitute structured light.

22. Optical impression taking device according to any one of the preceding claims, characterized in that Fresnel lenses are placed in front of the light sources (3').

23. Optical impression taking device according to any one of the preceding claims, characterized in that the light measurement sensors of the optical modules (1) are of the CCD or Cmos type.

24. Optical impression taking device according to any one of the preceding claims, characterized in that the optical modules (1) comprise at least one static or dynamic optical system of the lens or fiber type associated with the light measurement sensors.

25. Optical impression taking device according to any one of the preceding claims, characterized in that polarizing filters are placed in front of the light sources (3') and in front of the light sensors, the polarizing filters placed in front of the light sensors filtering the light signal in a direction that is perpendicular to the direction of filtering of the filters placed in front of the light sources (3').

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