Calibration unit for a macroscopic dental imaging device, macroscopic dental imaging calibration system, and use of the calibration unit

Abstract

To provide a calibration unit for the calibration of a macroscopic medical imaging device.SOLUTION: A calibration unit 28 comprises a main body 40 having a front surface 42 configured for being optically oriented towards an imaging device. Moreover, a fluorescent material 54 of a first type is arranged in a first sector 48 of the main body. Furthermore, a fluorescent material of a second type is arranged in a second sector 56 of the main body. Alternatively or additionally to the fluorescent material of the second type, an opaque, non-fluorescent material 68 is arranged in a third sector 66 of the main body. Additionally, a macroscopic dental imaging calibration system is presented. Moreover, a use of the calibration unit as described above for the calibration of the macroscopic dental imaging device is explained.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The present invention is directed to a calibration unit for calibration of a macroscopic medical imaging device, in particular for calibration of a macroscopic dental imaging device.

[0002] The present invention further relates to a macroscopic medical imaging calibration system, in particular to a macroscopic dental imaging calibration system.

[0003] The present invention further also relates to the use of a calibration unit as described above.

[0004] The imaging device described above is referred to as macroscopic to be understood as a differentiation from a microscopic imaging device or simply a microscope. Therefore, the present invention does not relate to a microscopic imaging device.

Background Art

[0005] Macroscopic medical imaging devices, in particular macroscopic dental imaging devices, are known. Such devices are used to take images of the human body or a part thereof. The content of the image may be analyzed, and by doing so, certain diseases or pathogens in the image may be recognized. When the medical imaging device is a dental imaging device, it is particularly adapted to take images of the human oral cavity or a part thereof.

[0006] In the context of macroscopic dental imaging devices, intraoral cameras, extraoral cameras, and so-called intraoral scanners may be used as imaging devices for taking images of the oral cavity or a part thereof.

[0007] Such imaging devices may be used to generate white light images of the intraoral environment.

[0008] Furthermore, not only healthy teeth but also certain dental pathogens are known to be fluorescent. In this context, fluorescence is understood as the ability of a material to emit light or more generally electromagnetic radiation when excited by light or more generally electromagnetic radiation. Such materials at least partially absorb the excitation light or radiation. In most cases, the emitted light or radiation has a longer wavelength than the absorbed light or radiation. Based on this effect, fluorescence images of the oral cavity or a part thereof can also be taken.

[0009] Both types of images are used to assist in diagnosis.

Summary of the Invention

Problems to be Solved by the Invention

[0010] An object of the present invention is to further improve a macroscopic dental imaging device so as to be able to obtain particularly high-quality fluorescence images.

Means for Solving the Problems

[0011] This problem is solved by a calibration unit for the calibration of a macroscopic medical imaging device, in particular a macroscopic dental imaging device. The calibration unit comprises a body having a front face configured to be optically oriented towards the imaging device. A first type of fluorescent material is arranged in a first sector of the body. Further, a second type of fluorescent material is arranged in a second sector of the body. The first sector and the second sector are separate from each other, and the first type of fluorescent material is different from the second type of fluorescent material. In addition to or instead of the second sector and the second type of fluorescent material, an opaque non-fluorescent material is arranged in a third sector of the body. The third sector is separate from each of the first sector and the second sector. Note that the terms first, second, and third are used only for ease of explanation. These terms do not mean specific numbered materials or sectors. A sector is understood as a volume part of the body. The sector may have any shape. Using such a calibration unit, the macroscopic medical imaging device, in particular the macroscopic dental imaging device, can be calibrated against the ground truth represented by the calibration unit. Thus, when two or more macroscopic medical imaging devices or two or more macroscopic dental imaging devices are calibrated using the same or similar calibration units, the comparability of the images generated by these imaging devices is improved. That is, an image taken by one imaging device can be compared with an image taken by another imaging device with high reliability. Also, since macroscopic medical imaging devices and macroscopic dental imaging devices may be calibrated more than once over time, using a calibration unit also improves the comparability of images taken at different times. That is, using a calibration unit has the effect of making the images taken comparable over time and between devices. Furthermore, the images taken with the calibrated imaging device can also be quantitatively analyzed. In the case of a macroscopic dental imaging device, dental pathogens represented in the image can be quantified.This enhances the diagnosis based on the image. According to the above description, by using the calibration unit, quantitative analysis can also be made comparable between different times or devices. In this way, the quality of the images captured by the macroscopic medical imaging device or the macroscopic dental imaging device is improved.

[0012] In this context, the first type of the fluorescent material, the second type of the fluorescent material, and / or the opaque non-fluorescent material may be selected to mimic the optical properties of either the healthy part of the human body or the biological part that is unhealthy due to a wide range of diseases or pathogens.

[0013] In the context of a macroscopic dental imaging device, the first type of the fluorescent material may mimic the fluorescence characteristics of healthy teeth. Note that healthy teeth emit light in the green spectrum when excited by light in the UV spectrum or the blue spectrum, for example, light having a wavelength of 200 nm to 500 nm.

[0014] The second type of the fluorescent material may mimic the fluorescence characteristics of the first dental pathogen, and the opaque non-fluorescent material may mimic the optical properties of the second dental pathogen. As an example, the second type of the fluorescent material can mimic the fluorescence characteristics of carious lesions. Compared with healthy teeth, the fluorescence emission of teeth with carious lesions shows a shift to the red spectrum when excited by ultraviolet, blue, or green spectrum light. Advanced carious lesions show bright red fluorescence due to the presence of porphyrins produced by cariogenic bacteria. The same applies to dental calculus and dental plaque.

[0015] The opaque non-fluorescent material may mimic the optical properties of so-called white spot lesions. Compared with healthy teeth, the luminescence of teeth with white spot lesions shows a decrease in green fluorescence due to light scattering in the affected enamel.

[0016] In all of the above embodiments, the calibration unit enables extremely precise calibration of the macroscopic medical imaging device. This is because the calibration unit is designed to provide fluorescence characteristics corresponding to or close to actual usage examples. That is, the wavelength or spectrum at which the imaging device is calibrated is equal to or close to the wavelength or spectrum that needs to be captured during the use of the imaging device.

[0017] According to one embodiment, a light-transmissive material is disposed in the fourth sector of the main body. The fourth sector is separate from each of the first sector, the second sector, and the third sector. Preferably, the light-transmissive material is also transparent. In this case, the light-transmissive material can be used to mimic enamel, which is also transparent. As a result, in dental applications, pathogens or diseases occurring under the surface of the tooth, i.e., under the enamel, can be mimicked by the calibration unit. Therefore, the imaging device can be calibrated using the calibration unit so that subsurface pathogens or diseases can be detected with high reliability.

[0018] In one example, at least one of the first sector, the second sector, and the third sector is at least partially surrounded by the fourth sector. In this context, the light-transmissive or transparent material of the fourth sector may also be used to hold together some or all of the remaining sectors, i.e., the first sector, the second sector, the third sector, or any combination thereof. Furthermore, this configuration leads to the realization of a highly compact calibration unit.

[0019] According to a modification example, the main body includes at least one auxiliary sector, and the first type of the fluorescent material, the second type of the fluorescent material, or the opaque non-fluorescent material is disposed within the auxiliary sector. In other words, the first type of the fluorescent material, the second type of the fluorescent material, or the opaque non-fluorescent material may be disposed in an additional sector. The auxiliary sector is understood to be separate from all other sectors. As a result, when performing calibration using the calibration unit, the calibration regarding the material of the auxiliary sector can be based on two sectors disposed at different positions. As a result, the uniformity of calibration across the field of view of the imaging device can be enhanced.

[0020] It should be noted that the present invention is not limited to the first type of fluorescent material and the second type of fluorescent material. Depending on the application, it is also possible to use additional types of fluorescent materials with optical properties suitable for mimicking the optical effects of the human body used in imaging.

[0021] At least one of the first sector, the second sector, the third sector, the fourth sector, and the auxiliary sector may be formed as a layer of the main body. This layer may extend parallel to the front surface. Such a layer can be manufactured in an efficient manner. Furthermore, by providing one of the sectors in the form of a layer, the calibration unit becomes compact.

[0022] The layer may be disposed at a distance from the front surface. Thus, in dental applications, pathogens or diseases occurring beneath the tooth surface may be mimicked by the material of the sector formed as such a layer. The same applies to general medical applications. By using the calibration unit, the imaging device can be calibrated so that pathogens or diseases beneath the surface can be detected with high reliability. Preferably, the space formed between the front surface and such a layer may be filled with a light-transmitting or transparent material, for example, the light-transmitting or transparent material of the fourth sector.

[0023] At least one of the first sector, the second sector, the third sector, and the auxiliary sector may be in a cylindrical shape, a conical shape, a polyhedral shape, or an ellipsoidal shape. By using such shapes, it becomes easy to embed at least one of the first sector, the second sector, the third sector, and the auxiliary sector into the fourth sector, and a compact calibration unit is formed. At the same time, the types of calibration targets become relatively numerous.

[0024] In this context, the front surface may coincide with an end surface of at least one of the first sector, the second sector, the third sector, and the auxiliary sector. This means that from the perspective of the imaging device calibrated using the calibration unit, the end surface of at least one of the first sector, the second sector, the third sector, and the auxiliary sector is not covered. Such a sector can be used to mimic pathogens or diseases that normally occur on the surface of a part of the human body, particularly the tooth surface. Thereby, the reliability of calibration is improved.

[0025] According to a modification example, a part of the front surface that coincides with at least one end surface of the first sector, the second sector, the third sector, and the auxiliary sector is locally curved. The part of the front surface may be curved convexly, that is, it may bulge outward toward the outside of the calibration unit. Alternatively, the part of the front surface may be curved concavely, that is, it may form a depression in the calibration unit. The part of the front surface that coincides with at least one end surface of the first sector, the second sector, the third sector, and the auxiliary sector may instead include a plurality of curved parts, for example, a plurality of parts bulging outward, or a plurality of depressions. It is also possible that some parts bulge outward and some parts form depressions. Since human teeth also have bumps and depressions, the reliability of calibration is further improved.

[0026] In an alternative example, the end surface facing the front surface of at least one of the first sector, the second sector, the third sector, and the auxiliary sector may be arranged at a distance from the front surface. Therefore, in dental applications, pathogens or diseases occurring under the tooth surface may be mimicked by the material of the sector having such an end surface. The same applies to general medical applications. By using the calibration unit, the imaging device can be calibrated so that pathogens or diseases under the surface can be detected with high reliability. Preferably, the space formed between the front surface and such an end surface can be filled with a light-transmitting or transparent material, for example, the light-transmitting or transparent material of the fourth sector.

[0027] In a preferred embodiment, the first sector is formed as a layer disposed at a distance from the front face and covering the entire width of the body. In this example, the fourth sector can also be formed as a layer, and the fourth sector completely fills the space between the front face and the first sector. The second sector may be completely or partially embedded in the fourth sector. Further, alternatively or additionally, the third sector may be completely or partially embedded in the fourth sector. Further, alternatively or additionally, at least one of the auxiliary sectors may be completely or partially embedded in the fourth sector. Such a calibration unit provides a plurality of calibration targets while being compact and easy to manufacture.

[0028] In one embodiment, the first type of the fluorescent material is a green fluorescent material. As already described, healthy teeth also contain a green fluorescent material. Therefore, the green fluorescent material is particularly suitable for mimicking the fluorescence characteristics of healthy teeth. Thus, an imaging device calibrated by the calibration unit according to the present invention can detect healthy teeth with high reliability.

[0029] In another embodiment, the second type of the fluorescent material is a red fluorescent material. As already described, carious lesions also contain a red fluorescent material. Therefore, the red fluorescent material is particularly suitable for mimicking the fluorescence characteristics of carious lesions. Thus, an imaging device calibrated by the calibration unit according to the present invention can detect carious lesions with high reliability.

[0030] According to one embodiment, at least one of the first sector, the second sector, the third sector, the fourth sector and the auxiliary sector comprises a dental restoration material. The dental restoration material usually mimics the properties of natural dental materials. Therefore, the material of the calibration unit is similar to the material to be inspected. This improves the image quality.

[0031] The dental restoration material may be a photo-curing material or a photo-polymerizable material. Such materials are cured by blue light or ultraviolet light. Examples of such materials are Tetric Prime, Petric EvoFlow, Tetric Powerfill, Tetric Powerflow, and Tetric EvoCeram. All of these materials are commercially available products of Ivoclar Vivadent AG (Liechtenstein).

[0032] The dental restoration material may be an inorganic material such as metal, ceramic, glass, glass-ceramic, etc. Examples of such materials are IPS e.max CAD, IPS e.max ZirCAD Prime, IPS Empress CAD, and IPS InLine. All of these materials are commercially available products of Ivoclar Vivadent AG (Liechtenstein).

[0033] The dental restoration material may be a two-component system material. In such materials, when two components are mixed, a redox reaction is initiated. Examples of such materials are Variolink and Teliolink. These materials are also commercially available products of Ivoclar Vivadent AG (Liechtenstein).

[0034] The dental restoration material may be a thermosetting material. Such materials need to be heated to cure. An example of such a material is SR Ivocap, a commercially available product of Ivoclar Vivadent AG (Liechtenstein). Further examples are Opti-Cryl and Veracryl, commercially available products of New Stetic S.A. of Colombia.

[0035] All of the above materials can be cured in a certain shape. Thereafter, the cured material may be subjected to a machining process or a cutting process such as milling, drilling, or grinding to reach the desired final shape.

[0036] In a further embodiment, the dental restoration material is a pre-cured material. Such materials are typically cured in a certain shape. Thereafter, the material can be processed subtractively, for example, by machining or cutting. An example of such a material is Tetric CAD, a commercial product of Ivoclar Vivadent AG (Liechtenstein).

[0037] As an alternative to the above materials which are specific dental restoration materials, different types of plastic materials may be used. Preferably, the plastic materials are suitable for injection molding and / or 3D printing. Examples of such materials include, but are not limited to, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polytetrafluoroethylene, polymethyl methacrylate, polyamide, polyester, polycarbonate, polyethylene terephthalate, polyoxymethylene, etc. Silicone can also be used.

[0038] As a further alternative to the above materials which are specific dental restoration materials, different types of inorganic materials may also be used. Preferably, the inorganic materials are machinable by milling and / or grinding, or processable through viscous flow by using hot press technology. Examples of such materials include, but are not limited to, silicate glasses and glass ceramics including lithium silicate glass ceramics, lithium aluminosilicate glass ceramics, leucite glass ceramics, and oxide ceramics including ZrO2, Al2O3 and feldspar ceramics.

[0039] As the first type of fluorescent material or as the second type of fluorescent material, phosphorescent substances may be used. For example, as phosphorescent substances that emit light in the green spectrum, zinc sulfide added with gold, copper or aluminum, such as ZnS:Cu+, ZnS:Au+, ZnS:Al3+ can be mentioned. As phosphorescent substances that emit light in the red spectrum, for example, yttrium oxide added with europium, such as Y2O2:Eu3+ can be mentioned.

[0040] The fluorescent material of the first type or the fluorescent material of the second type can be embedded in a dental restoration material.

[0041] At least one of the first sector, the second sector, and the third sector can also contain a pigment. These are non-fluorescent, but supplying a pigment is useful when using white light imaging in addition to fluorescence imaging. When known pigments are supplied to the calibration unit, color balance, particularly white balance, can be performed during calibration. Examples of white pigments include titanium dioxide and zinc oxide.

[0042] This problem is solved by a macroscopic medical imaging calibration system, in particular a macroscopic dental imaging calibration system. The macroscopic medical imaging calibration system comprises at least one imaging device, at least one calibration unit according to the invention, and at least one excitation device. The at least one excitation device is configured to excite the fluorescence of the fluorescent material of the first type. Further, the imaging device is configured to capture the excitation emission of the fluorescent material of the first type. The macroscopic medical imaging calibration system is a system for calibrating a macroscopic medical imaging device. Similarly, the macroscopic dental imaging calibration system is a system for calibrating a macroscopic dental imaging device. Here too, the term macroscopic is used as a differentiation from a microscopic imaging device or simply a microscope. When using such a macroscopic medical imaging calibration system, in particular a macroscopic dental imaging calibration system, the imaging device can be calibrated against the ground truth represented by the calibration unit. Thus, when two or more imaging devices are calibrated using the same or similar calibration units, the comparability of the images generated by these imaging devices is improved. That is, an image captured by one imaging device can be compared with high reliability with an image captured by another imaging device. Also, since the calibration of the imaging device may be performed multiple times over time, the comparability of images captured at different times is also improved. Further, the images captured by the calibrated imaging device can also be quantitatively analyzed. In the case of a macroscopic dental imaging device, dental pathogens represented in the image can be quantified. This enhances the diagnosis based on the image. According to the above description, by using the calibration unit, quantitative analysis is also comparable between times or devices. In this way, the quality of the images captured by a macroscopic medical imaging device or a macroscopic dental imaging device is improved.

[0043] It should be noted that the imaging device and the excitation device are introduced as separate devices. This is only one modification example. It is also possible to integrally form the imaging device and the excitation device into one device. Such a device may be called a camera device or a fluorescence imaging system.

[0044] Furthermore, it should be noted that the macroscopic medical imaging calibration system according to the present invention can also be configured to perform white balance. In this context, the imaging device is configured to capture a white light image. The sector of the calibration unit made of the opaque non-fluorescent material may be used for this purpose. Alternatively, a white balancing sector may be provided in the calibration unit. Such a white balancing sector may be specifically adapted to perform white balance.

[0045] In a modification example, at least one excitation device may be further configured to excite the fluorescence of a second type of fluorescent material. Furthermore, the imaging device may be configured to capture the excitation emission of the second type of fluorescent material. Therefore, the fluorescence imaging function related to the fluorescence of the second type of fluorescent material can also be calibrated. As a result, the quality of the fluorescence image is further improved.

[0046] In a further alternative, two separate excitation devices are provided, one of the excitation devices being configured to excite the fluorescence of a first type of fluorescent material and the other of the excitation devices being configured to excite the fluorescence of a second type of fluorescent material.

[0047] When the calibration unit includes a sector having a first type of fluorescent material and a sector having a second type of fluorescent material, a method for calibrating an imaging device includes exciting the first type of fluorescent material, photographing the excitation emission of the first type of fluorescent material, and, if necessary, adapting the settings of at least one of the imaging devices. Thereafter, the method includes exciting the second type of fluorescent material, photographing the excitation emission of the second type of fluorescent material, and, if necessary, adapting the settings of at least one of the imaging devices. In other words, the first type of fluorescent material and the second type of fluorescent material are then excited. In the above example, the first type of fluorescent material is excited before the second type of fluorescent material. Of course, this order can be reversed. By exciting sequentially, the fluorescence from the first type of fluorescent material and the fluorescence from the second type of fluorescent material do not affect each other, so that a high-quality calibration result can be obtained. In an alternative example, the first type of fluorescent material and the second type of fluorescent material are excited together. In an alternative in this case, only the fluorescence of one of these materials is photographed in a first step, and the fluorescence of the other material is photographed in a second step. A filter may be used for this purpose. In other alternatives, the fluorescence of both materials is photographed together. Since the fluorescence emission of the materials is characterized by different wavelengths, one or more filters may be used to separate the emissions from each other. Also, such variations enable high-quality calibration.

[0048] In this context, the imaging device can be one of an intraoral camera, an extraoral camera, and an intraoral scanner. Such an imaging device is suitable for use in dental diagnosis.

[0049] This problem is further solved by using the calibration unit according to the present invention for the calibration of a macroscopic medical imaging device, in particular a macroscopic dental imaging device. By using such a calibration unit, a macroscopic medical imaging device, in particular a macroscopic dental imaging device, can be calibrated with respect to the ground truth represented by the calibration unit. Therefore, when two or more macroscopic medical imaging devices or two or more macroscopic dental imaging devices are calibrated using the same or similar calibration units, the comparability of the images generated by these imaging devices is improved. That is, an image taken by one imaging device can be compared with an image taken by another imaging device with high reliability. In addition, since a macroscopic medical imaging device or a macroscopic dental imaging device may be calibrated more than once over time, using the calibration unit also improves the comparability of images taken at different times. That is, using the calibration unit has the effect of making the captured images comparable over time and between devices. Furthermore, the images taken by the calibrated imaging device can also be quantitatively analyzed. In the case of a macroscopic dental imaging device, dental pathogens represented in the image can be quantified. This enhances the diagnosis based on the image. According to the above description, the calibration unit enables quantitative analysis to be comparable over time and between devices. In this way, the quality of the images taken by a macroscopic medical imaging device or a macroscopic dental imaging device is improved.

[0050] It is understood that during the use of the calibration unit, it is necessary to block the ambient light from affecting the optical interaction between the calibration unit and the imaging device. By blocking the ambient light, the quality of the calibration is further improved.

[0051] The calibration performed using the calibration unit may be at least one of calibration of pixel size, calibration of color sensitivity, and calibration of color intensity.

Brief Description of the Drawings

[0052] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

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Embodiments for Carrying Out the Invention

[0053] FIG. 1 shows a macroscopic medical imaging calibration system 10, and in the embodiment shown in the drawings, a macroscopic dental imaging calibration system 10 is shown. Note that the same reference numerals are used for the macroscopic medical imaging calibration system and the macroscopic dental imaging calibration system.

[0054] The macroscopic dental imaging calibration system 10 includes a camera device 12.

[0055] The camera device 12 is a combination of an imaging device 14 having an image acquisition optical system 16 and an excitation device 18. In this embodiment, the excitation device has a plurality of excitation diodes 20 (see FIG. 2).

[0056] The camera device 12 shown in FIGS. 1 and 2 is an extraoral camera.

[0057] The macroscopic dental imaging calibration system 10 includes a masking device 22 realized as a masking box 24 in the embodiment shown in FIG. 1.

[0058] The masking device 22 has a container 26 that houses the calibration unit 28 and an opening 30 that receives a part of the camera device 12.

[0059] Furthermore, the masking device 22 includes a number of walls 32 that do not allow light to pass through. The walls 22 surround the container 26 on all sides except for the opening 30. Therefore, the masking device 22 can prevent ambient light from affecting the calibration of the camera device 12, particularly the imaging device 14 that uses the calibration unit 28.

[0060] In the embodiment of FIG. 1, one wall 32 shown on the upper side of the masking device 22 is hingedly connected to an adjacent wall 32 so that it can be selectively opened to place the calibration unit 28 inside the container 26 and to withdraw the calibration unit 28 from the container 26.

[0061] In FIG. 1, the upper wall is shown as if it were transparent so that the inside of the masking device 22 can be seen. The upper wall is in a closed state.

[0062] Also, the open state of the upper wall is shown by a dashed line.

[0063] FIG. 3 shows a variant of the dental imaging calibration system 10.

[0064] This variant differs from the variant shown in FIG. 1 only in that the masking device 22 is formed as a masking sleeve 34 made of a light-impermeable flexible material.

[0065] The masking sleeve 34 has a closed end 36 and an open end 38 disposed on the opposite side of the closed end 36.

[0066] In use, the calibration unit 28 is disposed adjacent to the closed end 36 inside the masking sleeve 34, and a part of the camera device 12 is received in the open end 38. Therefore, the masking sleeve 34 can also prevent ambient light from affecting the calibration of the camera device 12, particularly the imaging device 14 that uses the calibration unit 28.

[0067] FIG. 4 shows an alternative example of the camera device 12 formed as an intraoral camera.

[0068] The camera device 12 in FIG. 4 is also a combination of an imaging device 14 having an image acquisition optical system 16 and an excitation device 18. Here too, the excitation device 18 has a plurality of excitation diodes 20.

[0069] It is understood that the camera device 12 in FIG. 4 may be used in place of the camera device 12 shown in FIGS. 1 to 3. When using the camera device in FIG. 4, the end of the camera device 12 provided with the image acquisition optical system 16 and the excitation diodes 20 is arranged inside the shielding box 24 through the opening 30, or inserted from the open end 38 and arranged inside the shielding sleeve 34.

[0070] The macroscopic dental imaging calibration system 10 in all the modifications also includes a calibration unit 28 which is only schematically shown in FIGS. 1 and 3.

[0071] Hereinafter, different embodiments of the calibration unit 28 will be described with reference to FIGS. 5 to 17.

[0072] A first embodiment of the calibration unit 28 is shown in FIGS. 5 to 7.

[0073] In this embodiment, the calibration unit 28 includes a main body 40 having a shape generally as a circular disk.

[0074] The main body 40 has a front surface 42 which is the upper surface in the view of FIG. 5, and a rear surface 44 which is the lower surface in the view of FIG. 5.

[0075] Between the front surface 42 and the rear surface 44, a side surface 46 having a circular cross-section and a tube shape extends.

[0076] The front surface 42 is configured to be optically directed towards the imaging device 14, that is, the camera device 12 (see also FIGS. 1 and 3).

[0077] The calibration unit 28 includes a first sector 48.

[0078] In this embodiment, the first sector is formed as a layer of the main body 40.

[0079] This layer is ring-shaped and has an opening 50 at its center.

[0080] The first sector 48 extends parallel to the front surface 42 and parallel to the rear surface 44.

[0081] At the same time, the rear surface 44 of the main body 40 is formed by the lower surface of the first sector 48, that is, the first sector 48 is disposed at the lower end of the main body 40.

[0082] The thickness of the first sector 48 formed as an annular layer extends over approximately half of the thickness of the disk-shaped main body 40. Therefore, the first sector 48 is disposed at a distance from the front surface 42.

[0083] In this embodiment, the first sector 48 is made of a dental restoration material 52 in which particles 54 of a first type of fluorescent material are embedded. For better visibility, reference numerals are attached only to some of the particles 54 of the first type of fluorescent material.

[0084] The dental restoration material is a material that substitutes for dentin.

[0085] The first type of fluorescent material 54 is a green fluorescent material.

[0086] The calibration unit 28 also includes a second sector 56.

[0087] The second sector 56 has a cylindrical shape.

[0088] The diameter of the cylinder matches the diameter of the opening 50, and the cylinder forming the second sector 56 is disposed within the opening 50 such that the lower surface of the second sector 56 coincides with the rear surface 44.

[0089] Also, the upper end surface of the cylinder forming the second sector 56 coincides with the front surface 42.

[0090] Therefore, the second sector 56 extends between the rear surface 44 and the front surface 42. In other words, the height of the cylinder forming the second sector 56 matches the thickness of the main body 40.

[0091] In this embodiment, the second sector 56 is made of a dental restoration material 52 in which particles 58 of a second type of fluorescent material are embedded. For better visibility, reference numerals are attached only to some of the particles 58 of the second type of fluorescent material.

[0092] The second type of fluorescent material 58 is a red fluorescent material.

[0093] Therefore, the second type of fluorescent material 58 is different from the first type of fluorescent material 54.

[0094] Furthermore, the calibration unit 28 includes a fourth sector 60.

[0095] Note that the sectors are numbered as the first, second, and fourth only for the sake of ease of explanation. It does not mean the specific number of sectors.

[0096] The fourth sector 60 is also formed as a layer of the main body 40.

[0097] The layer is ring-shaped and has an opening 62 at the center.

[0098] The first sector 48 and the fourth sector 60 are arranged in a congruent state.

[0099] That is, the outer diameters of the first sector 48 and the fourth sector 60 are the same. Also, the diameters of the opening 50 and the opening 62 are the same.

[0100] The fourth sector 60 extends parallel to the front surface 42 and parallel to the rear surface 44.

[0101] At the same time, the front surface 42 of the main body 40 is formed by the upper surface of the fourth sector 60. The lower surface of the fourth sector 60 coincides with the upper surface of the first sector 48.

[0102] Therefore, the thickness of the fourth sector 60 formed as an annular layer also extends over approximately half of the thickness of the disk-shaped main body 40.

[0103] The second sector 56 penetrates the opening 62. In other words, the fourth sector 60 partially surrounds the second sector 56.

[0104] In this embodiment, the fourth sector is made of a light-transmissive material 64, particularly a transparent material.

[0105] Note that the first sector 48, the second sector 56, and the fourth sector 60 are separate from each other.

[0106] In the calibration unit 28 according to the first embodiment, the first sector 48 mimics a healthy tooth. The second sector 56 mimics a carious lesion, and the fourth sector 60 mimics enamel.

[0107] By using such a calibration unit 28, the imaging device 14 can be calibrated with high reliability.

[0108] A second embodiment of the calibration unit 28 is shown in FIGS. 8 to 10.

[0109] Hereinafter, only the differences from the first embodiment will be described. The same or corresponding elements are denoted by the same reference numerals.

[0110] The second embodiment is different from the first embodiment in that the upper end surface of the second sector 56 is arranged at a distance d from the front surface 42. Therefore, the height of the second sector 56 having a cylindrical shape is shorter than the thickness of the main body 40.

[0111] The space between the upper end face of the second sector 56 and the front face 42 then forms part of the fourth sector 60 and is filled with a translucent, more specifically a transparent material 64. In other words, the opening 62 is then a blind hole.

[0112] Therefore, although the second sector 56 is covered in part by the fourth sector 60, it is visible in FIGS. 8 and 9.

[0113] In the calibration unit 28 according to the second embodiment, the first sector 48 also mimics a healthy tooth and the fourth sector 60 mimics enamel.

[0114] The second sector 56 mimics a subsurface carious lesion. Such a lesion is covered by enamel.

[0115] Even when using the calibration unit 28 of the second embodiment, the imaging device 14 can be calibrated with high reliability.

[0116] A third embodiment of the calibration unit 28 is shown in FIGS. 11 to 13.

[0117] Here too, only the differences with respect to the first and second embodiments will be described. Identical or corresponding elements are given the same reference numerals.

[0118] Compared with the first and second embodiments, now the first sector 48 is disc-shaped, i.e., the first sector 48 does not have an opening 50.

[0119] The fourth sector 60 corresponds to the fourth sector 60 of the first embodiment.

[0120] However, instead of the second sector 56, a third sector 66 is provided.

[0121] The third sector 66 is cylindrical and is arranged in the opening 62 of the fourth sector 60.

[0122] The third sector 66 completely fills the opening 62.

[0123] The upper end face of the third sector 66 coincides with the front face 42. The lower end face of the third sector 66 coincides with the lower end face of the fourth sector 60.

[0124] In this embodiment, the third sector 66 is made of an opaque non-fluorescent material 68.

[0125] Note that the third sector 66 is separate from the first sector 48 and the fourth sector 60.

[0126] In the calibration unit 28 according to the third embodiment, the first sector 48 mimics a sound tooth. The third sector 66 mimics a white spot lesion, and the fourth sector 60 mimics enamel.

[0127] By using such a calibration unit 28, the imaging device 14 can be calibrated with high reliability.

[0128] A fourth embodiment of the calibration unit 28 is shown in FIGS. 14 to 17.

[0129] As before, only the differences from the previous embodiments will be described. The same or corresponding elements are denoted by the same reference numerals.

[0130] The calibration unit 28 according to the fourth embodiment includes a first sector 48 corresponding to the first sector of the third embodiment of the calibration unit, that is, the first sector 48 of the fourth embodiment of the calibration unit 28 is in the shape of a disk without an opening.

[0131] In addition, the calibration unit 28 according to the fourth embodiment includes a third sector 66 corresponding to the third sector 66 of the third embodiment. Therefore, the third sector 66 has a cylindrical shape and is disposed at the center within the calibration unit 28.

[0132] In addition, the calibration unit 28 according to the fourth embodiment is composed of a total of four second sectors 56.

[0133] The first pair P1 of the second sectors 56 is disposed on the first diameter D1 of the calibration unit 28. One of the second sectors 56 forming a part of the first pair P1 is disposed on the first side surface side of the third sector 66 between the third sector 66 and the side surface 46. The other second sector 56 forming a part of the first pair P1 is disposed on the opposite side surface side of the third sector 66 between the third sector 66 and the side surface 46.

[0134] The second sectors 56 of the first pair P1 each have a cylindrical shape.

[0135] The upper end surfaces of the second sectors 56 of the first pair P1 coincide with the front surface 42. The lower end surfaces of the second sectors 56 of the first pair P1 coincide with the upper end surfaces of the first sectors 48.

[0136] The second pair P2 of the second sectors 56 is disposed on the second diameter D2 of the calibration unit 28.

[0137] The second diameter D2 extends substantially orthogonally to the first diameter D1.

[0138] One of the second sectors 56 forming a part of the second pair P2 is disposed on the first side surface side of the third sector 66 between the third sector 66 and the side surface 46. The other second sector 56 forming a part of the second pair P2 is disposed on the opposite side surface side of the third sector 66 between the third sector 66 and the side surface 46.

[0139] The second sectors 56 of the second pair P2 each have a cylindrical shape.

[0140] The upper end surfaces of the second sectors 56 of the second pair P2 are arranged at a distance d from the front surface 42 (see the second embodiment of the calibration unit 28). The lower end surfaces of the second sectors 56 of the first pair coincide with the upper end surfaces of the first sectors 48.

[0141] The diameters of all the second sectors 56 are substantially the same.

[0142] When comparing the calibration unit 28 of the fourth embodiment with the calibration units of the first and second embodiments, the calibration unit 28 of the fourth embodiment is further configured to include three more second sectors 56. Therefore, the second to fourth second sectors 56 can also be called auxiliary sectors 70.

[0143] The calibration unit 28 of the fourth embodiment also includes a fourth sector 60. The fourth sector 60 is formed as a layer as in the previous embodiments.

[0144] In the fourth embodiment, the fourth sector 60 consists of five openings, and the central opening 62 accommodates the third sector 66 as in the third embodiment.

[0145] The remaining openings 72, 74, 76, 78 each accommodate one of the second sectors 56.

[0146] In this context, the openings 72, 74 each accommodate the second sector 56 of the first pair P1. These openings are formed as through holes.

[0147] The openings 76, 78 each receive the second sector 56 of the second pair P2. These openings are formed as blind holes.

[0148] In the calibration unit 28 according to the fourth embodiment, the first sector 48 mimics a sound tooth. The third sector 66 mimics a white spot lesion, and the fourth sector 60 mimics enamel.

[0149] The second sector 56 of the first pair P1 mimics a surface caries lesion, and the second sector 56 of the second pair P2 mimics a subsurface caries lesion.

[0150] When using such a calibration unit 28, the imaging device 14 can be calibrated with high reliability. With the auxiliary sector 70, the calibration is particularly uniform across the field of view of the imaging device 14.

[0151] The calibration unit 28 of all the above embodiments can be used to calibrate the camera device 12, more specifically the imaging device 14.

[0152] For this reason, the excitation device 18 is configured to excite the fluorescence of the first type of fluorescent material 54 and the second type of fluorescent material 58.

[0153] Furthermore, the imaging device 14 is configured to capture the excitation emission of the first type of fluorescent material 54 and the second type of fluorescent material 58.

[0154] When using the calibration unit 28 according to the first, second, and fourth embodiments to calibrate the camera device 12, the excitation device 18 is used to excite both the first type of fluorescent material 54 and the second type of fluorescent material 58.

[0155] In the first step, only the excitation emission of the first type of fluorescent material 54 may be captured using the imaging device 14.

[0156] In the second step, only the excitation emission of the second type of fluorescent material 58 may be captured using the imaging device 14.

[0157] To photograph only one of the excitation emissions of the fluorescent materials 54 and 58, a filter may be used.

[0158] The calibration performed using the calibration unit 28 may be at least one of pixel size calibration, color sensitivity calibration, and color intensity calibration.

Explanation of Signs

[0159] 10 Macroscopic medical imaging calibration system, macroscopic dental imaging calibration system 12 Camera device 14 Imaging device 16 Image acquisition optical system 18 Excitation device 20 Excitation diode 22 Masking device 24 Masking box 26 Container 28 Calibration unit 30 Aperture 32 Wall 34 Masking sleeve 36 Closed end of the masking sleeve 38 Open end of the masking sleeve 40 Body of the calibration unit 42 Front surface 44 Rear surface 46 Side surface 48 First sector 50 Aperture 52 Dental restoration material 54 First type of fluorescent material 56 Second sector 58 Second type of fluorescent material 60 Fourth sector 62 Aperture 64 Translucent material 66 Third sector 68 Opaque non-fluorescent material 70 Auxiliary sector 72 Aperture 74 Aperture 76 opening 78 opening d distance D1 first diameter D2 second diameter P1 first pair P2 second pair

Claims

1. A calibration unit (28) for calibrating a macroscopic dental imaging device (14), comprising a body (40) having a front surface (42) configured to be optically directed towards the macroscopic dental imaging device (14), A first type of fluorescent material (54) is disposed in a first sector (48) of the body (40), the first sector (48) being a volume portion of the body (40), and a. A second type of fluorescent material (58) is disposed in a second sector (56) of the body (40), the second sector (56) being a volume portion of the body (40), the first sector (48) and the second sector (56) being separate from each other, and the first type of fluorescent material (54) being different from the second type of fluorescent material (58), and / or b. An opaque non-fluorescent material (68) is disposed in a third sector (66) of the body (40), the third sector (66) being a volume portion of the body (40), the third sector (66) being separate from each of the first sector (48) and the second sector (56), the calibration unit.

2. The calibration unit (28) according to claim 1, wherein a light-transmissive material (64) is disposed in a fourth sector (60) of the body (40), the fourth sector (60) being a volume portion of the body (40), and the fourth sector (60) being separate from each of the first sector (48), the second sector (56), and the third sector (66), the calibration unit.

3. The calibration unit (28) according to claim 2, wherein at least one of the first sector (48), the second sector (56), and the third sector (66) is at least partially surrounded by the fourth sector (60), the calibration unit.

4. In the calibration unit (28) according to any one of claims 1 to 3, the main body (40) includes at least one auxiliary sector (70), the auxiliary sector (70) is a volume part of the main body (40), and the first type of the fluorescent material (54), the second type of the fluorescent material (58) or the opaque non-fluorescent material (68) is disposed in the auxiliary sector (70).

5. In the calibration unit (28) according to any one of claims 1 to 3, at least one of the first sector (48), the second sector (56), and the third sector (66) is formed as a layer of the main body (40), and the layer extends parallel to the front surface (42).

6. In the calibration unit (28) according to claim 5, the layer is disposed at a distance from the front surface (42).

7. In the calibration unit (28) according to any one of claims 1 to 3, at least one of the first sector (48), the second sector (56), and the third sector (66) is cylindrical, conical, polyhedral, or ellipsoidal.

8. In the calibration unit (28) according to claim 7, the front surface (42) coincides with at least one end surface of the first sector (48), the second sector (56), and the third sector (66).

9. In the calibration unit (28) according to claim 7, an end surface of at least one of the first sector (48), the second sector (56), and the third sector (66) facing the front surface (42) is disposed at a distance (d) from the front surface (42).

10. In the calibration unit (28) according to any one of claims 1 to 3, the calibration unit, wherein the first type of the fluorescent material is a green fluorescent material.

11. The calibration unit (28) according to any one of claims 1 to 3, the calibration unit, wherein the second type of the fluorescent material is a red fluorescent material.

12. In the calibration unit (28) according to any one of claims 1 to 3, the calibration unit, wherein at least one of the first sector (48), the second sector (56), and the third sector (66) comprises a dental restoration material (52).

13. A macroscopic dental imaging calibration system (10) comprising at least one imaging device (14), at least one calibration unit (28) according to any one of claims 1 to 3, and at least one excitation device (18), The at least one excitation device (18) is configured to excite fluorescence of the first type of the fluorescent material (54), The imaging device (14) is configured to capture the excitation emission of the first type of the fluorescent material (54), A macroscopic dental imaging calibration system.

14. In the macroscopic dental imaging calibration system (10) according to claim 13, the macroscopic dental imaging calibration system, wherein the imaging device (14) is one of an intraoral camera, an extraoral camera, and an intraoral scanner.

15. A method of using the calibration unit (28) according to any one of claims 1 to 3 for calibrating a macroscopic dental imaging device (14).

Images