Imaging tray with medium disposed therein for ratiometric determination of object shape
The attenuation and other optical properties of a medium are exploited to measure a thickness of the medium between a sensor and a target surface. Disclosed herein are various mediums, arrangements of hardware, and processing techniques that can be used to capture these thickness measurements and obtain three-dimensional images of the target surface in a variety of imaging contexts. This includes general techniques for imaging interior/concave surfaces as well as exterior/convex surfaces, as well as specific adaptations of these techniques to imaging ear canals, human dentition, and so forth.
1. A device comprising:
an imaging tray having a bottom and a sidewall forming an interior surface including a fluorescent surface of known dimensions that fluoresces over a range of wavelengths including a first wavelength of light and a second wavelength of light;
a medium disposed within the interior surface, the medium capable of yielding to form an impression of an object inserted into the imaging tray, wherein the medium absorbs the first wavelength of light more than a second wavelength of light;
a light source for illuminating the medium;
a camera adapted to capture one or more images of the medium at the first wavelength and the second wavelength; and
a processor programmed to use the one or more images, in view of the known dimensions of the interior surface, to determine a shape of the object based upon a ratio of an intensity of the first wavelength and an intensity of the second wavelength in one or more directions.
2. The device of claim 1 wherein the imaging tray is shaped and sized for use as a dental bite tray.
3. The device of claim 1 wherein the medium is capable of curing to retain the impression when the object is removed from the imaging tray.
4. The device of claim 1 wherein the imaging tray includes a plurality of fiducials at known locations within the imaging tray.
5. The device of claim 4 wherein the plurality of fiducials provide visible landmarks to an imaging system.
6. The device of claim 1 wherein at least one of the sidewall and the bottom are transparent.
7. The device of claim 1 wherein the interior surface has a known, uniform color.
8. The device of claim 1 wherein the medium includes a single fluorescent dye.
9. The device of claim 1 wherein the medium includes a plurality of fluorescent dyes.
10. A method comprising:
disposing a medium within an imaging tray having an interior surface of known dimensions having a fluorescent substance disposed thereon that fluoresces over a range of wavelengths including a first wavelength of light and a second wavelength of light, the medium capable of yielding to form an impression of an object inserted into the imaging tray, and the medium absorbing the first wavelength of light more than the second wavelength of light;
inserting the object into the imaging tray;
illuminating the interior surface of the imaging tray;
capturing an image of the interior surface at the first wavelength and the second wavelength; and
processing the image to determine a thickness of the medium in a direction of the interior surface based on a ratio of an intensity of the first wavelength and the second wavelength.
11. The method of claim 10 further comprising:
obtaining a plurality of thickness measurements for a plurality of directions toward the interior surface; and
applying the plurality of thickness measurements, in view of the known dimensions of the interior surface, to determine a three-dimensional shape of the object.
12. The method of claim 10 further comprising:
providing a plurality of fiducials within the imaging tray;
capturing a reference image of the plurality of fiducials; and
using the reference image to determine a three-dimensional position and orientation of the imaging tray.
13. The method of claim 12 wherein the reference image is the image of the interior surface at the first wavelength and the second wavelength.
14. The method of claim 10 wherein inserting the object into the imaging tray includes inserting human dentition into a dental bite tray.