COLOUR REFERENCE FOR CALIBRATING A DENTAL COLOUR CAMERA

Abstract

The invention relates to a color reference for calibrating a dental color camera comprising a plurality of fields. A surface of the color reference comprises color fields for color calibration as well as white fields and/or gray fields for a white balance and/or a shading correction.

Claims

1. Color reference for calibrating a dental color camera comprising a plurality of fields having a first color field and a second color field, wherein a surface of the color reference includes color fields for color calibration and white fields and/or gray fields for white balance and/or shading correction, wherein the white fields and/or the gray fields are evenly distributed over the surface of the color reference.

2. Color reference according to claim 1, wherein the color fields include at least three different colors.

3. Color reference according to claim 1, wherein the plurality of fields have a rectangular shape, wherein the color fields and the white fields and/or the gray fields are alternately arranged relative to one another, in the form of a checkerboard.

4. Color reference according to claim 3, wherein the plurality of fields have a square shape.

5. Color reference according to claim 1, wherein the plurality of fields are immediately adjacent to one another.

6. Color reference according to claim 1, wherein the color reference further comprises a holder, wherein the holder is configured to be attached to a color camera in order to arrange the color reference at a defined distance and with a defined orientation relative to the color camera.

7. Method for calibrating a dental color camera using the color reference according to claim 1, wherein the method comprises the steps of: recording the color reference by a dental color camera, producing an optical image, determining a color value and/or at least one brightness value for at least one pixel of at least four of the recorded white fields and/or gray fields and the white balance and/or the shading correction, determining an actual color value for at least three recorded color fields by comparing with a stored target color value for each respective color field, determining white balance calibration values and/or shading calibration values for pixels of the optical image for carrying out the white balance and/or the shading correction and color calibration values for every color of the color fields, wherein the white balance and the shading correction are carried out across the entire surface of an image field of the dental color camera, wherein, based on the color values and/or the brightness values of the white fields and/or the gray fields, an interpolation algorithm is used to determine a white balance and a shading correction over the entire image field, which also includes regions of the color fields.

8. Method according to claim 7, wherein each of the plurality fields of the recorded optical image are segmented using a segmentation algorithm.

9. Method according to claim 7, wherein the color reference further comprises a holder, wherein the color reference is arranged at a defined distance and with a defined orientation relative to the color camera by means of the holder prior to recording the optical image in such a way that the depiction of the color reference in the optical image covers the entire image field.

10. Method according to claim 9, wherein the color reference is arranged perpendicular to a recording direction of the color camera by means of the holder.

11. Method according to any one of claim 7, wherein calibration data is obtained for the entire image field after the white balance, the shading correction and the color calibration are carried out.

12. Method according to claim 11, wherein the obtained calibration data is stored in a memory to be used to correct the optical images of the color camera.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The invention will be explained with reference to the drawings. The drawings show:

[0058] FIG. 1 a color reference in the form of a plate for calibrating a dental color camera,

[0059] FIG. 2 a color reference having square fields,

[0060] FIG. 3 a color reference having rectangular fields,

[0061] FIG. 4 a color reference having diamond-shaped fields.

DESIGN EXAMPLES

[0062] FIG. 1 shows a color reference 1 in the form of a plate for calibrating a dental color camera 2, comprising color fields 3 and white fields 4. In the depicted embodiment, the fields 3 and 4 are square-shaped and are arranged relative to one another in the manner of checkerboard. A holder 5 is disposed on the color reference 1 and can be attached to the color camera 2 in such a way that the color reference 1 can be arranged at a defined distance 6 and with a set orientation relative to the color camera 2. The color reference 1 is arranged in such a way that the fields 3 and 4 of the color reference 1 cover the entire image field 7 of the color camera 2, whereby the boundaries of the image field 7 are indicated by the dashed lines.

[0063] FIG. 2 shows a further embodiment of the color reference 1, wherein the color fields 3 and the white fields 4 are arranged in four lines and five rows in the manner of a checkerboard, wherein the fields 3 and 4 are square-shaped.

[0064] FIG. 3 shows a further embodiment of the color reference 1, wherein the color fields 3 and the white fields 4 are shaped like elongated rectangles and are arranged in three lines and eight rows in the manner of a checkerboard.

[0065] FIG. 4 shows a further embodiment of the color reference 1, wherein the color fields 3 are shown hatched and the white fields 4 are diamond-shaped and are arranged in the manner of a checkerboard.

REFERENCE SIGNS

[0066] 1 Color reference [0067] 2 Color camera [0068] 3 Color fields [0069] 4 White fields [0070] Holder [0071] 6 Distance [0072] 7 Image field