METHOD, SYSTEM AND COMPUTER PROGRAM FOR DETERMINING A REFLECTANCE DISTRIBUTION FUNCTION OF AN OBJECT

• US 20140354801A1
• Filed: 05/31/2013
• Published: 12/04/2014
• Est. Priority Date: 05/31/2013
• Status: Active Grant

• Current Assignee: Artmyn SA (Auction Holdings, Inc.)
• Original Assignee: Ecole polytechnique fãdãrale de lausanne epfl (Schweizerische Eidgenossenschaft)
• Inventors: Vetterli, Martin, Prandoni, Paolo, BABOULAZ, Loic A.
• Granted Patent: US 10,107,747 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

The invention refers to a method for analysing reflected light of an object. First a light angle distribution for a point of the object is determined. Then a plenoptic projector is controlled to illuminate the point of the object with the determined light angle distribution. Then the reflected light intensity of the point of the object is measured and the measured reflected light is analysed in dependence of the determined light angle distribution.

Claims

1. Method for analysing reflected light of an object, comprising the steps of:

determining a light angle distribution for a point of the object;

controlling a plenoptic projector to illuminate the point of the object with the determined light angle distribution;

measuring the reflected light intensity of the point of the object; and

analysing the reflected light in dependence of the determined light angle distribution.

2. Method according to claim 1, wherein the determined light angle distribution at the point of the object is a determined extended light angle distribution around one illumination direction.

3. Method according to claim 2, wherein the point of the object is illuminated sequentially from different illumination directions with the determined extended light angle distribution, and the reflectance distribution function at the point of the object at an observation direction is determined by the deconvolution of the measured reflected light distribution over the different illumination directions at the point of the object at the observation direction with the determined extended light angle distribution.

4. Method according to claim 1, wherein the plenoptic projector comprises a display, a microlense array and a main lense, wherein each pixel of the display is projected by a microlense of the microlense array and by the main lense with a light angle corresponding to the pixel to a point of the object corresponding to the pixel, and the light intensity of each pixel of a group of pixels of the display corresponding to said point of the object is controlled such that it corresponds to the light intensity of the light angle corresponding to said pixel of the light angle distribution.

5. Method according to claim 4, wherein the point is sequentially illuminated at different illumination directions by controlling the group of pixels corresponding to the point such that light is sequentially emitted by different subgroups of this group of pixels.

6. Method according to claim 1, wherein the group of pixels illuminating the point are determined on the basis of the relative three-dimensional position of the point to the plenoptic projector.

7. Method according to claim 1, wherein the plenoptic projector creates a light angle distribution at each point of at least an area of the object.

8. Method according to claim 7, wherein the plenoptic projector creates different light angle distributions at different points of the object.

9. Method according to claim 7, wherein the measured reflected light distribution of each point of the object is captured by a photographic camera, especially a plenoptic camera.

10. Method according to claim 1, wherein the reflected light intensity of the point of the object is measured by a plenoptic camera.

11. Method according to claim 10, wherein the reflected light at different observation directions are measured at the same time with the plenoptic camera, and the reflected light at the point of the object at the different observation angles is analysed in dependence of the determined light angle distribution.

12. Method according to claim 10, wherein the plenoptic projector creates a light angle distribution at each point of at least an area of the object, and the reflected light at different observation directions and at each point of the at least one area of the object are measured at the same time with the plenoptic camera, and the reflected light at each point of at least an area of the object at the different observation angles is analysed in dependence of the determined light angle distribution of each point of the at least one area.

13. System for analysing reflected light of an object, comprising:

a plenoptic projector comprising a display, a microlense array and a main lense arranged such that each pixel of the display is projected by a microlense of the microlense array and by the main lense with a light angle corresponding to the pixel to a point of the object corresponding to the pixel;

a light sensor for measuring the reflected light intensity of the point of the object;

a processor for controlling the light intensity of each pixel of a group of pixels of the display corresponding to a point of the object such that it corresponds to the light intensity of the light angle corresponding to said pixel of a determined light angle distribution and for analysing the reflected light in dependence of the determined light angle distribution.

14. System according to claim 13, wherein the determined light angle distribution at the point of the object is a determined extended light angle distribution around one illumination direction.

15. System according to claim 14, wherein the processor is configured such that the point of the object is illuminated sequentially from different illumination directions with the determined extended light angle distribution, and that a reflectance distribution function at the point of the object at an observation direction is determined by a deconvolution of the measured reflected light distribution over the different illumination directions at the point of the object at the observation direction with the determined extended light angle distribution.

16. System according to claim 13, wherein the processor is configured such that the point of the object is sequentially illuminated at different illumination directions by controlling the group of pixels corresponding to the point such that light is sequentially emitted by different subgroups of this group of pixels.

17. System according to claim 13, wherein the group of pixels illuminating the point are determined on the basis of the relative three-dimensional position of the point to the plenoptic projector.

18. System according to claim 13, wherein the processor is configured to control the plenoptic projector such that the plenoptic projector creates a light angle distribution at each point of at least an area of the object.

19. System according to claim 18, wherein the processor is configured to control the plenoptic projector such that the plenoptic projector creates different light angle distributions at different points of the object.

20. System according to claim 18, wherein the light sensor is a photographic camera, especially a plenoptic camera, configured to measure the reflected light distribution of each point of the area.

21. System according to claim 13, wherein the light sensor is a plenoptic camera configured such that the reflected light intensity of the point of the object is measured under different observation directions at the same time.

22. System according to claim 13, wherein the processor is configured to control the plenoptic projector such that the plenoptic projector creates a light angle distribution at each point of at least an area of the object, and to measure via the plenoptic camera the reflected light at different observation directions and at each point of the at least one area of the object at the same time, and to analyse the reflected light at each point of at least an area of the object at the different observation angles in dependence of the determined light angle distribution of each point of the at least one area.

23. Non-transitory computer program configured to perform the following steps when run on a processor:

determining a light angle distribution for a point of the object;

sending signals out to control a plenoptic projector to illuminate the point of the object with the determined light angle distribution;

receiving a measured reflected light intensity of the point of the object; and

analysing the reflected light in dependence of the determined light angle distribution.