METHOD AND REFERENCE MODEL FOR CHECKING A MEASURING SYSTEM

• US 20140365140A1
• Filed: 01/28/2013
• Published: 12/11/2014
• Est. Priority Date: 01/27/2012
• Status: Active Grant

• Current Assignee: Sirona Dental Systems GmbH (Sirona Dental Systems Incorporated)
• Original Assignee: Sirona Dental Systems GmbH (Sirona Dental Systems Incorporated)
• Inventors: Popilka, Bjrn, Wedler, Volker, Adamson, Anders, Thiel, Frank
• Granted Patent: US 9,462,993 B2
• Time in Patent Office: Days
• US Class Current: 702/19
• CPC Class Codes: A61B 2560/0233 Optical standards
• CPC Class Codes: A61B 5/1077 Measuring of profiles
• CPC Class Codes: A61B 5/1079 using optical or photographic means
• CPC Class Codes: A61B 6/582 Calibration
• CPC Class Codes: A61C 13/34 Making or working of models, e.g. preliminary castings, trial dentures; Dowel pins [4]
• CPC Class Codes: A61C 19/04 Measuring instruments specially adapted for dentistry A61C5/44 takes precedence; testing vitality of teeth A61B5/0534; radiation diagnosis specially adapted for dentistry A61B6/51
• CPC Class Codes: A61C 9/006 projecting one or more stripes or patterns on the teeth
• CPC Class Codes: A61C 9/0066 Depth determination through adaptive focusing
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G06T 19/20 Editing of 3D images, e.g. changing shapes or colours, aligning objects or positioning parts
• CPC Class Codes: G06T 2207/30036 Dental; Teeth
• CPC Class Codes: G06T 2207/30204 Marker
• CPC Class Codes: G06T 2219/2004 Aligning objects, relative positioning of parts
• CPC Class Codes: G06T 7/80 Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
• CPC Class Codes: G06T 7/85 Stereo camera calibration
• CPC Class Codes: G09B 23/283 for dentistry or oral hygiene G09B23/286 takes precedence

Abstract

The invention relates to a reference object (3) and a method for checking a measuring system (1), wherein a plurality of three-dimensional recordings (4, 8) of a reference object are recorded from different recording directions (5) by means of the measuring system (1). The reference object (3) has a closed shape, wherein each of the three-dimensional recordings (4) is registered with at least the preceding recording (4). In the case of a faulty calibration and/or in the case of a faulty registration, the individual recordings (4, 8) are deformed compared to the actual shape of the reference object (3), so that the deformation continues when assembling the individual three-dimensional recordings (4) to form an overall recording (54) and the generated overall recording (54) deviates in its dimensions from the dimensions of the reference object (3) as a result thereof. At least one object region (10) of the reference object (3) is measured twice, at the beginning of a circuit and at the end of the circuit, wherein a distance (55) is determined in the overall recording (54) between a first position of the object region (10) in a first recording at the beginning of the circuit and a second position of the object region (10) in a second recording at the end of the circuit.

Claims

1. A method to check a measuring system comprising:

recording multiple three-dimensional images of a closed shaped reference object from different image directions in a circuit along the reference object using the measuring system, wherein at least one object region of the reference object is measured twice, at the start of the circuit and at the end of the circuit;

registering each of the three-dimensional images at least with a previous one of the three-dimensional images so that the three-dimensional images are combined into an overall image, wherein a faulty calibration and/or a faulty registration causes the individual three-dimensional images to be deformed in comparison with an actual shape of the reference object and the deformation of the individual three-dimensional images causes a deviation in the dimensions of the overall image from the dimensions of the reference object;

determining a distance in the overall image between a first position of the object region in an image from the start of the circuit and a second position of the object region in an image from the end of the circuit; and

determining a measuring error of the measuring system, the measuring error including a calibration error and a registration error, using the distance, wherein before completion of the three-dimensional images, the registration error is determined by (i) cutting out virtual, individual sub-regions one after the other from a first original virtual 3-D model of the reference object, each sub-region partially overlapping with a previous sub-region and with a following sub-region, (ii) registering each sub-region with at least one previous sub-region so that a second virtual 3-D model of the reference object is generated after registration (iii) determining the registration error from a deviation between the first original 3-D model and the second 3-D model of the reference object, and (iv) determining the calibration error by subtracting the registration error from the total measuring error.

2. The method according to claim 1, wherein the reference object is ring-shaped and provides models of multiple teeth next to one another in a row.

3. The method according to claim 2, wherein a trajectory of the measuring system proceeds in a circle around the ring-shaped reference object during recording of the images from different image directions.

4. The method according to claim 1, wherein the reference object corresponds to a conventional articulator with a closed upper jaw and lower jaw.

5. The method according to claim 4, wherein a trajectory of the measuring system proceeds along the shape of the articulator during recording of the three-dimensional images from different image directions.

6. The method according to claim 1, wherein an image direction of a last image in a sequence of the three-dimensional images corresponds to an image direction of a first image in the sequence.

7. The method according to claim 1, wherein a first image region of a first image in a sequence of the three-dimensional images corresponds, at least partially, to an image region of a following image.

8. The method according to claim 1, wherein the dimensions of the sub-regions correspond to image regions of the individual three-dimensional images to be recorded.

9. The method according to claim 1, wherein each three-dimensional image partially overlaps with a first preceding three-dimensional image and with a second preceding three-dimensional image that precedes the first preceding three-dimensional image, and wherein the method further comprises registering each three-dimensional image with the first preceding three-dimensional image and with the second preceding three-dimensional image.

10. A reference model for checking a dental measuring system, the reference model comprising:

multiple models of teeth, wherein

the reference model is in the shape of a ring, and

the models of teeth are arranged next to one another in a row along the circumference of the reference model.

11. (canceled)