3D IMAGING USING STRUCTURED LIGHT FOR ACCURATE VEHICLE OCCUPANCY DETECTION

• US 20130307932A1
• Filed: 05/21/2012
• Published: 11/21/2013
• Est. Priority Date: 05/21/2012
• Status: Active Grant

• Current Assignee: Conduent Business Services, LLC (Conduent, Inc.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: MESTHA, Lalit Keshav, ZHAO, Yonghui
• Granted Patent: US 9,007,438 B2
• Time in Patent Office: Days
• US Class Current: 348/46
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G06V 20/593 Recognising seat occupancy
• CPC Class Codes: G06V 20/64 Three-dimensional objects
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

What is disclosed is a method which combines structured illumination in the SWIR wavelength range with the detection capabilities of NIR to generate a 3D image of a scene for accurate vehicle occupancy determination. In one embodiment, structured light is projected through a customized optical element comprising a patterned grid. Wavelengths of the received structured pattern are shifted to a CCD detectable range. The shifted light comprises an image in a structured pattern. The wavelength-shifted light is detected using an infrared detector operating in the NIR. For each pixel in the detected patterned image, an amount of distortion caused by 3D surface variation at this pixel location is determined. The distortion is converted to a depth value. The process repeats for all pixels. A 3D image is constructed using each pixel'"'"'s depth value. The number of occupants in the vehicle is determined from the constructed 3D image.

Claims

1. A method for 3D imaging of an occupant in a motor vehicle for vehicle occupancy determination, the method comprising:

projecting an illumination light source onto a motor vehicle intended to be analyzed for vehicle occupancy determination, said illumination source comprising structured light in the Short Wave Infrared (SWIR), said structured light being projected through an optical element comprising a patterned grid, a reflection of said source light being sensed by an imaging sensor;

shifting said sensed reflected source light to a wavelength range of a CCD device, said wavelength-shifted light being an image in a structured pattern;

using an infrared detector operating in the near infrared range of 700-1000 nm to detect said wavelength-shifted light;

for each pixel in said structured patterned image;

analyzing said detected wavelength-shifted light to determine an amount of distortion caused by 3D surface variation at this pixel location; and

converting said distortion to a depth value for this pixel;

constructing a 3D image using each pixel'"'"'s respective depth value; and

determining a number of occupants in said vehicle by analyzing said 3D image.

2. The method of claim 1, wherein said Short Wave Infrared band is tuned to an available wavelength converter range of 1495 to 1550 nm.

3. The method of claim 1, wherein wavelengths of said pattern are converted to a CCD detectable range using a phosphor coated converter which shifts the received light to a Si-based CCD detectable wavelength range.

4. The method of claim 1, wherein, in order to enhance a contrast, an intensity curve of said illumination projector is altered with a gamma transformation

5. The method of claim 1, further comprising calibrating said light source to recover the linearity of illumination intensity.

6. The method of claim 1, further comprising calibrating said projected patterns comprising:

projecting at least one test pattern;

capturing said projected pattern by said imaging sensor;

determining a relationship between actual intensity of said projected patterns and pixel intensity values;

fitting said established relationship with a high order polynomial function;

calculating an inverse function; and

using said inverse function to rectify said pattern to be projected.

7. The method of claim 1, further comprising determining whether a traffic violation has occurred based upon said determined number of occupants.

8. The method of claim 7, further comprising alerting an authority in the instance wherein a traffic violation has occurred.

9. A system for 3D imaging of an occupant in a motor vehicle for vehicle occupancy determination, the system comprising:

an illumination light source comprising structured light in the Short Wave Infrared (SWIR), said structured light being projected through an optical element comprising a patterned grid, said illumination light source projecting structured light onto a motor vehicle intended to be analyzed for vehicle occupancy determination;

an imaging sensor for sensing a reflection of said light source;

an infrared detector operating in the near infrared range of 700-1000 nm; and

a processor in communication with a memory for executing machine readable instructions for performing;

shifting said sensed reflected source light to a wavelength range of a CCD device, said wavelength-shifted light being an image in a structured pattern;

using an infrared detector operating in the near infrared range of 700-1000 nm to detect said wavelength-shifted light;

for each pixel in said structured patterned image;

analyzing said detected wavelength-shifted light to determine an amount of distortion caused by 3D surface variation at this pixel location; and

converting said distortion to a depth value for this pixel;

constructing a 3D image using each pixel'"'"'s respective depth value; and

determining a number of occupants in said vehicle by analyzing said 3D image.

10. The system of claim 9, wherein said Short Wave Infrared band is tuned to an available wavelength converter range of 1495 to 1550 nm.

11. The system of claim 9, wherein wavelengths of said pattern are converted to a CCD detectable range using a phosphor coated converter which shifts the received light to a Si-based CCD detectable wavelength range.

12. The system of claim 9, wherein, in order to enhance a contrast, an intensity curve of said illumination projector is altered with a gamma transformation.

13. The system of claim 9, further comprising calibrating said light source to recover the linearity of illumination intensity.

14. The system of claim 9, further comprising calibrating said projected patterns comprising:

projecting at least one test pattern;

capturing said projected pattern by said imaging sensor;

determining a relationship between actual intensity of said projected patterns and pixel intensity values;

fitting said established relationship with a high order polynomial function;

calculating an inverse function; and

using said inverse function to rectify said pattern to be projected.

15. The system of claim 9, further comprising determining whether a traffic violation has occurred based upon said determined number of occupants.

16. The system of claim 15, further comprising alerting an authority in the instance wherein a traffic violation has occurred.

17. A computer implemented method for 3D imaging of an occupant in a motor vehicle for vehicle occupancy determination, the method comprising:

projecting an illumination light source onto a motor vehicle intended to be analyzed for vehicle occupancy determination, said illumination source comprising structured light in the Short Wave Infrared (SWIR), said structured light being projected through an optical element comprising a patterned grid, a reflection of said source light being sensed by an imaging sensor;

shifting said sensed reflected source light to a wavelength range of a CCD device using a phosphor coated converter which shifts the received light to a Si-based CCD detectable wavelength range, said wavelength-shifted light being an image in a structured pattern;

using an infrared detector operating in the near infrared range of 700-1000 nm to detect said wavelength-shifted light;

for each pixel in said structured patterned image;

analyzing said detected wavelength-shifted light to determine an amount of distortion caused by 3D surface variation at this pixel location; and

converting said distortion to a depth value for this pixel;

constructing a 3D image using each pixel'"'"'s respective depth value; and

determining a number of occupants in said vehicle by analyzing said 3D image.

18. The computer implemented method of claim 17, wherein, in order to enhance a contrast, an intensity curve of said illumination projector is altered with a gamma transformation.

19. The computer implemented method of claim 17, wherein said Short Wave Infrared band is tuned to an available wavelength converter range of 1495 to 1550 nm.

20. The computer implemented method of claim 17, further comprising calibrating said light source to recover the linearity of illumination intensity.

21. The computer implemented method of claim 17, further comprising calibrating said projected patterns comprising:

projecting at least one test pattern;

capturing said projected pattern by said imaging sensor;

determining a relationship between actual intensity of said projected patterns and pixel intensity values;

fitting said established relationship with a high order polynomial function;

calculating an inverse function; and

using said inverse function to rectify said pattern to be projected.

22. The computer implemented method of claim 17, further comprising determining whether a traffic violation has occurred based upon said determined number of occupants.

23. The computer implemented method of claim 17, further comprising alerting an authority in the instance wherein a traffic violation has occurred.