Detection of projected infrared patterns using difference of Gaussian and blob identification

A system comprising:

• one or more infrared projectors configured to project a dot pattern and a flood pattern;
• an infrared image sensor;
• and
• a processor configured to perform operations comprising:
• operating the one or more infrared projectors to project the dot pattern or the flood pattern onto an object;
• operating the infrared image sensor to capture an infrared image of the object;
• determining a difference of Gaussian image that represents features of the infrared image that have spatial frequencies within a spatial frequency range defined by a first Gaussian operator and a second Gaussian operator;
• identifying one or more blob regions within the difference of Gaussian image, wherein each blob region of the one or more blob regions comprises a region of connected pixels in the difference of Gaussian image;
• and
• based on identifying the one or more blob regions within the difference of Gaussian image, determining whether the infrared image represents the object illuminated by the dot pattern or the flood pattern projected onto the object by the one or more infrared projectors.

A non-transitory computer-readable storage medium having stored thereon instructions that, when executed by a computing device, cause the computing device to perform operations comprising:

• obtaining an infrared image of an object;
• determining a difference of Gaussian image that represents features of the infrared image that have spatial frequencies within a spatial frequency range defined by a first Gaussian operator and a second Gaussian operator;
• identifying one or more blob regions within the difference of Gaussian image, wherein each blob region of the one or more blob regions comprises a region of connected pixels in the difference of Gaussian image;
• and
• based on identifying the one or more blob regions within the difference of Gaussian image, determining whether the infrared image represents the object illuminated by a dot pattern or a flood pattern projected onto the object by one or more infrared projectors.