METHOD OF MULTISPECTRAL IMAGING AND AN APPARATUS THEREOF

• US 20100073504A1
• Filed: 01/29/2008
• Published: 03/25/2010
• Est. Priority Date: 01/29/2007
• Status: Active Grant

• Current Assignee: Jong-Il Park, Michael Grossberg, Moon Hyun Lee, Shree K. Nayar
• Original Assignee: Jong-Il Park, Michael Grossberg, Moon Hyun Lee, Shree K. Nayar
• Inventors: Lee, Moon Hyun, Nayar, Shree K., Grossberg, Michael, Park, Jong-Il
• Granted Patent: US 8,284,279 B2
• Time in Patent Office: Days
• US Class Current: 348/222.100
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means

Abstract

A multispectral imaging method and system is provided. A multispectral imaging method of the present invention includes determining an on-off combination of a plurality of light sources illuminating a scene; illuminating the scene with the light sources according to the on-off combination selected on the basis of a first control signal generated by a microcontroller; capturing an image of the scene by operating a camera on the basis of a second control signal synchronized with the first control signal; determining a plurality of spectral basis functions and weights of the spectral basis functions; and acquiring a continuous spectral reflectance by summing values obtained by multiplying the spectral basis functions and respective weights. The multispectral imaging method of the present invention is practical and efficient in that a continuous spectral reflectance image can be acquired with a minimized number of measurements required for obtaining spectral reflectance. Accordingly, the multispectral imaging method of the present invention can be applied to various fields, such as image reproduction and medical imaging, while overcoming performance limits of the conventional RGB imaging techniques.

Claims

1. A multispectral imaging method comprising:

determining an on-off combination of a plurality of light sources illuminating a scene;

illuminating the scene with the light sources according to the on-off combination selected on the basis of a first control signal generated by a microcontroller;

capturing an image of the scene by operating a camera on the basis of a second control signal synchronized with the first control signal;

determining a plurality of spectral basis functions and weights of the spectral basis functions; and

acquiring a continuous spectral reflectance by summing values obtained by multiplying the spectral basis functions and respective weights.

2. The multispectral imaging method of claim 1, wherein the weights are determined using known spectral response characteristics of a camera and spectra to the plurality of lights sources.

3. The multispectral imaging method of claim 1, wherein the spectral basis functions are derived from a corresponding model showing linear characteristics to a spectral reflectance of the scene.

4. The multispectral imaging method of claim 3, wherein the spectral basis functions are eigenvectors of a correlation matrix derived from a database of spectral reflectances of Munsell color chips.

5. The multispectral imaging method of claim 1, wherein the light sources constitute at least one light-emitting diode cluster.

6. The multispectral imaging method of claim 1, wherein the continuous spectral reflectance is calculated by an equation:

7. The multispectral imaging method of claim 1, wherein the on-off combination of the light sources to be illuminated to the scene is determined by a weight matrix minimizing offset of a spectral reflectance of a predetermined representative material to the spectral basis functions, camera channel, spectra of the light sources, and number of frames (N).

8. The multispectral imaging method of claim 7, wherein the light sources are characterized in that spectral response of each camera channel overlaps with at least one light source, the spectrum of the illumination is different for the frames, and a total power of illumination in a frame is comparable to that obtained when half the light sources are on.

9. A multispectral imaging system comprising:

a microcontroller which generates an on-off control signal indicating an on-off combination of light sources illuminating a scene and generates an operation control signal in synchronization with the on-off control signal;

a plurality of light sources that turn on according to the on-off combination indicated by the on-off control signal to illuminate the scene;

a camera which captures an image of the scene on the basis of the operation control signal; and

a multispectral image generator which determines a plurality of spectral basis functions and weights of the spectral basis functions, acquires a continuous spectral reflectance by summing values obtained by multiplying the spectral basis functions and respective weights.

10. The multispectral imaging system of claim 9, wherein the microcontroller comprises a light-emitting diode controller having a mast board and at least one slave board, the master board controlling the slave board by processing the user input, and the slave board controlling on/off of the light sources according to control signals generated by the master board.

11. The multispectral imaging system of claim 9, wherein the light sources constitutes at least one light-emitting diode cluster.

12. The multispectral imaging system of claim 9, wherein the camera comprises at least one RGB camera.

13. The multispectral imaging system of claim 9, wherein the spectral basis functions are derived from a corresponding model showing linear characteristics to a spectral reflectance of the scene.

14. The multispectral imaging system of claim 13, wherein the spectral basis functions are eigenvectors of a correlation matrix derived from a database of spectral reflectances of Munsell color chips.

15. The multispectral imaging system of claim 9, wherein the light sources are characterized in that spectral response of each camera channel overlaps with at least one light source, the spectrum of the illumination is different for the frames, and a total power of illumination in a frame is comparable to that obtained when half the light sources are on.