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EP0250993B1
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Method and apparatus for the three-dimensional representation and determination of prepared teeth
Assignee: Individual
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Filing: 1987-06-12
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Granted: 1991-11-13
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Expires: 2007-06-12
Abstract
Abstract The method provides a means for a dentist to record the shape in situ of teeth prepared for repair. During a search mode, a high resolution grey scale image is presented on a monitor. The scan head is positioned over the prepared cavity, using this visual feedback. A trigger initiates actual 3D data acquisition, which is accomplished in a fraction of a second using an active triangulation principle. The result is stored in congruent memory banks in the form of a 3D profile and a pseudoplastic grey scale image representing the back-scattered contrast. The pseudoplastic contrast image is displayed instantaneously on the monitor. The point to point relationship between the pseudoplastic grey scale image and the 3D profile allows use of the grey scale display as a drawing plane for operator data verification and editing. The contour lines defining the desired restorative implant appear as an overlay to the grey scale image, while the actual positional values of points on the contour lines are stored in and retrieved from the 3D profile. The contrast-derived pseudoplastic image not only provides higher intelligibility for the operator; but data processing algorithms can also make use for each image point of both sets of data, that is the 3D profile and the contrast image.
Inventors
- 👤 Marco Dr. Brandestini
- 👤 Werner H. Dr.med.dent. Mörmann
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 22:12
CPC Classifications
A; A61; A61C; A61C9/00; A61C9/004; A61C9/0046; A61C9/0053; A61C9/006; G; G16; G16H; G16H20/00; G16H20/40
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
185 words
Method for a three-dimensional imaging and representation of teeth, respectively of worked surfaces of the same and of their immediate neighbourhood, with the aid of a camera, for producing three-dimensional data for the manufacture of an insert body, where a reference pattern is projected in order to obtain depth information, characterized in that in order to determine an adequate viewing angle of the camera a moving video monitoring image, in which the superimposed projected pattern is not shown, is first generated and displayed on a monitor, and that upon receipt of a triggering signal a sequence of images is taken for generating and storing a set of data which on the one hand contains image information that corresponds to the last search image and can be represented as a contrast image on the monitor in order to be used as a base for drawing additional details, and which on the other hand contains depth values which are localized in correspondence with the image, so that an additional drawing made on the contrasted image defines the three-dimensional insert when taken in conjunction with the depth values.
Claim 2
Dependent Claim
185 words
Method for a three-dimensional imaging and representation of teeth, respectively of worked surfaces of the same and of their immediate neighbourhood, with the aid of a camera, for producing three-dimensional data for the manufacture of an insert body, where a reference pattern is projected in order to obtain depth information, characterized in that in order to determine an adequate viewing angle of the camera a moving video monitoring image, in which the superimposed projected pattern is not shown, is first generated and displayed on a monitor, and that upon receipt of a triggering signal a sequence of images is taken for generating and storing a set of data which on the one hand contains image information that corresponds to the last search image and can be represented as a contrast image on the monitor in order to be used as a base for drawing additional details, and which on the other hand contains depth values which are localized in correspondence with the image, so that an additional drawing made on the contrasted image defines the three-dimensional insert when taken in conjunction with the depth values.
Claim 3
Dependent Claim
45 words
Method according to claim 1, characterized in that for the obtention of a still image the contrast values, ie the light values, corrected for an undesirable secondary illumination, are imaged for each pixel, in order to generate a pseudosolid three-dimensional representation of the worked surface.
Claim 4
Dependent Claim
52 words
Method according to one of the preceding claims, characterized by the insertion of markers, which are fixed with respect to the image frame and which correspond to the stored image information, so that the video search image, respectively the data to be registered, can be adjusted with respect to the inserted markers.
Claim 5
Dependent Claim
62 words
Method according to one of the preceding claims, characterized in that one uses the still image as the image plane for the computer-aided addition of contour lines for the insert, where the contours of the insert body which are entered are complemented by pairing image points of the still image with corresponding depth values, in order to obtain a three-dimensional contour design.
Claim 6
Dependent Claim
47 words
Method according to any of claims 2 to 4, characterized in that for a further processing the depth values are being weighted with the help of the corresponding contrast values, so that the statistical value of each depth value depends on the strength of the corresponding contrast.
Claim 7
Dependent Claim
136 words
Device for implementing the method of any of the preceding claims, with a memory and a calculating unit (51 - 55, 57 - 63) , which determines the three-dimensional information for manufacturing the insert body from the registered image signals, by using the movable reference pattern projected in superimpression, characterized in that in order to suppress the reference pattern for a pattern-free representation of the monitoring video image on the monitor (56) means (40 - 44) for eliminating the reference pattern from the ray path, respectively means (4, 5, 11) for a time-integration of the registered image, are provided, and in that the memory and the calculation unit are so constructed that the three-dimensional data for manufacturing the insert body always correspond to the last pattern-free monitoring video image which was represented last on the monitor.
Claim 8
Dependent Claim
68 words
Device according to claim 6, characterized in that the memory and calculating unit comprises a calculating element (52 - 55, 57, 58) which, when activated by a trigger signal, is able to generate, store and represent in form of a still image on the monitor screen (56) a contrasted image which is in one-to-one correspondence with the last video image and which is corrected for unwanted secondary illumination.
Claim 9
Dependent Claim
61 words
Device according to claim 7, characterized in that the calculating element (52 - 55, 57, 58) is such that the contrasted image can be generated from several pictures taken in succession and with a shifted reference pattern, in order to eliminate reflected light and other artefacts, the contrasted image being in one-to-one correspondence with a relief generated from the depth values.
Claim 10
Dependent Claim
51 words
Device according to one of claims 7 and 8, characterized in that the calculating unit has access to two memory planes (54, 55), where any memory location of each corresponds to one image pixel, the contrasted image being stored in one memory plane, and the corresponding depth values in the other.
Claim 11
Dependent Claim
33 words
Device according to claim 9, characterized in that it comprises means to manually input and to store markers which are fixed relative to the image frame, and thereby superimposed on the image planes.
Claim 12
Dependent Claim
154 words
Device according to claim 9 or 10, characterized in that it comprises optical means (2 - 5, 40 - 44) introduced in the ray path of the camera in order to generate the reference pattern of light and shadows on the worked surface, and an optical device ( 7 - 9, 11) for imaging the same on an image sensor (11), characterized in that an optical image can be detected through the image sensor (11), upon a triggering signal occurring for different positions of the pattern, that each optical image can be stored in a storage plane (54, 55), whereby a circuit (50 - 63) generates, from the stored light values and by way of a transformation, a pair of values for each image point, one value of which represents the distance (z) of the image point to a reference plane, and the other value of which represents the local amplitude of the contrast.
Claim 13
Dependent Claim
61 words
Device according to any of claims 6 to 11, characterized in that the reference pattern of light and shadows can be generated through a mask (4) movably mounted in the ray path, characterized in that in order to generate the monitoring video image the mask (4) is movable synchronously with the image-taking frequency, such that the pattern is suppressed by integration.
Claim 14
Dependent Claim
46 words
Device according to any of claims 6 to 11, characterized in that the reference pattern of light and shadows can be generated by a liquid crystal cell (40 - 44) which is commanded so that it lets light pass when the video image is being generated.
Claim 15
Dependent Claim
46 words
Device according to claim 11 or 13, where the reference pattern is generated by a liquid crystal cell, characterized in that the liquid crystal cell (40 - 44) comprises an electrode pattern able to shift the pattern of light and shadows by fractions of its period.
References Cited (Backward Citations)
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