Methods and Apparatus for Imaging of Occluded Objects

• US 20140347676A1
• Filed: 05/27/2014
• Published: 11/27/2014
• Est. Priority Date: 05/24/2013
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Velten, Andreas, Raskar, Ramesh
• Granted Patent: US 9,274,047 B2
• Time in Patent Office: Days
• US Class Current: 356/614
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01J 3/021 using plane or convex mirrors, parallel phase plates, or particular reflectors
• CPC Class Codes: G01J 3/027 Control of working procedures of a spectrometer; Failure detection; Bandwidth calculation
• CPC Class Codes: G01J 3/10 Arrangements of light sources specially adapted for spectrometry or colorimetry
• CPC Class Codes: G01J 3/42 Absorption spectrometry; Double beam spectrometry; Flicker spectrometry; Reflection spectrometry beam switching arrangements G01J3/08
• CPC Class Codes: G01N 2021/3129 Determining multicomponents by multiwavelength light
• CPC Class Codes: G01N 2021/6417 Spectrofluorimetric devices
• CPC Class Codes: G01N 21/255 Details, e.g. use of specially adapted sources, lighting or optical systems
• CPC Class Codes: G01N 21/27 using photo-electric detection G01N21/31 takes precedence; circuits for computing concentration logarithmic circuits G06G7/24; photometric circuits in general G01J
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 21/64 Fluorescence; Phosphorescence
• CPC Class Codes: G01N 21/6456 Spatial resolved fluorescence measurements; Imaging
• CPC Class Codes: G01N 2201/061 Sources

Abstract

An active imaging system, which includes a light source and light sensor, generates structured illumination. The light sensor captures transient light response data regarding reflections of light emitted by the light source. The transient light response data is wavelength-resolved. One or more processors process the transient light response data and data regarding the structured illumination to calculate a reflectance spectra map of an occluded surface. The processors also compute a 3D geometry of the occluded surface.

Claims

1. A method comprising, in combination:

(a) using an active imaging system to generate structured illumination, which active imaging system includes a light sensor and a light source;

(b) using the light sensor to capture transient light response data regarding reflections of light emitted by the light source; and

(c) using one or more processors to process the transient light response data and data regarding the structured illumination to calculate a reflectance spectra map of an occluded surface.

2. The method of claim 1, wherein the set of transient light response data is wavelength-resolved.

3. The method of claim 1, wherein the one or more processors calculate three-dimensional spatial coordinates of each respective point in a set of points on the occluded surface.

4. The method of claim 1, wherein the light source is wavelength-resolved and wavelength-tunable.

5. The method of claim 1, wherein the light source emits a series of pulses of light, such that:

(a) the light source emits a first wavelength during a first set of the pulses of light and not during other pulses in the series;

(b) the light source emits a second wavelength during a second set of the pulses of light and not during other pulses in the series; and

(c) the light source emits a third wavelength during a third set of the pulses of light and not during other pulses in the series; and

(d) the first, second and third sets of pulses of light do not overlap each other.

6. The method of claim 1, wherein the light sensor is wavelength-resolved and wavelength-tunable.

7. The method of claim 1, wherein:

(a) the light sensor is wavelength-resolved and wavelength-tunable; and

(b) the light source is wavelength-resolved and wavelength-tunable.

8. The method of claim 1, wherein the one or more processors classify the occluded object based at least in part on the reflectance spectra map.

9. The method of claim 8, wherein the occluded surface comprises mammalian tissue.

10. The method of claim 1, wherein the one or more processors identify fluorescence that occurs in the occluded surface.

11. The method of claim 1, wherein the one or more processors identify a specific type of fluorescent material in the occluded surface, based at least on sensor data indicative of a specific absorption spectrum and specific emission spectrum of the occluded material.

12. The method of claim 1, wherein the one or more processors compute a reflectance spectra map for a visible surface.

13. The method of claim 1, wherein the active imaging system computes or detects a synthetic temporal detection pattern.

14. The method of claim 1, wherein the active imaging system computes or detects a synthetic wavelength band detection pattern.

15. The method of claim 1, wherein the active imaging system computes or detects a synthetic spatial detection pattern.

16. The method of claim 1, wherein the one or more processors perform an algorithm, which algorithm includes, for each data sample I (i) determining a set of voxels for which the distance of a three-bounce light path equals the product of c and t, and (ii) incrementing a calculated intensity of each respective voxel in the set of voxels by an amount equal to the product of I and α

, where;

(a) each data sample I is a measured intensity at a single pixel of the light sensor for a particular illumination wavelength band, illumination position, detection position and time t,

(b) c is a constant equal to the speed of light in a vacuum times a number, which number is greater than or equal to 0.9 and less than or equal to 1.0; and

(c) α

is (i) a constant or (ii) a variable that is dependent on at least distance between the respective voxel and a detection position.

17. A method comprising, in combination:

(a) using an active imaging system to generate structured illumination, which active imaging system includes a light sensor and a light source;

(b) using the light sensor to capture transient light response data regarding reflections of light emitted by the light source; and

(c) using one or more processors to process the transient light response data and data regarding the structured illumination to calculate 3D spatial coordinates of each respective point, out of a set of points on an occluded surface.

18. The method of claim 17, wherein the one or more processors compute a synthetic temporal detection pattern.

19. An active imaging system comprising, in combination:

(a) a light source for emitting light and a light sensor for capturing transient light response data regarding reflections of the light, which transient light response data is wavelength-resolved; and

(b) one or more processors for processing the data to calculate a reflectance spectra map of an occluded surface.

20. The active imaging system of claim 19, wherein the active illumination system is configured to generate structured illumination.