Spoof detection via 3d reconstruction

A method comprising:

• receiving, at one or more processing devices, a first sequence of images of a first subject captured by an image acquisition device over a time period in which relative locations of the image acquisition device with respect to the first subject varies;
• selecting, by the one or more processing devices, a first image and a second image from the first sequence of images, wherein the first image represents a first relative location of the image acquisition device with respect to the first subject, and the second image represents a second relative location, different from the first relative location, of the image acquisition device with respect to the first subject;
• generating, by the one or more processing devices and using the first image and the second image as a stereo pair, a first three-dimensional representation of the first subject using a photometric stereo process for estimating a three dimensional shape from two dimensional images;
• determining, based on the first three dimensional representation, that the first subject is an alternative representation of a live person;
• and
• responsive to determining that the first subject is an alternative representation of a live person, preventing access to a secure system.

An system comprising:

• an image acquisition device configured to capture a first sequence of images of a first subject over a time period in which relative locations of the image acquisition device with respect to the first subject varies;
• and
• an image analysis engine comprising one or more processing devices, wherein the image analysis engine is configured to:
• receive the first sequence of images,
• select a first image and a second image from the first sequence of images, wherein the first image represents a first relative location of the image acquisition device with respect to the first subject, and the second image represents a second relative location, different from the first relative location, of the image acquisition device with respect to the first subject,
• generate, using the first image and the second image as a stereo pair, a first three-dimensional representation of the first subject using a photometric stereo process for estimating a three dimensional shape from two dimensional images,
• determine, based on the first three dimensional representation, that the first subject is an alternative representation of a live person, and
• responsive to determining that the first subject is an alternative representation of a live person, prevent access to a secure system.

One or more non-transitory machine-readable storage devices having encoded thereon computer readable instructions for causing one or more processing devices to perform operations comprising:

• obtaining a first sequence of images of a first subject captured by an image acquisition device over a time period in which relative locations of the image acquisition device with respect to the first subject varies;
• selecting a first image and a second image from the first sequence of images, wherein the first image represents a first relative location of the image acquisition device with respect to the first subject, and the second image represents a second relative location, different from the first relative location, of the image acquisition device with respect to the first subject;
• generating, using the first image and the second image as a stereo pair, a first three-dimensional representation of the first subject using a photometric stereo process for estimating a three dimensional shape from two dimensional images;
• determining, based on the first three dimensional representation, that the first subject is an alternative representation of a live person;
• and
• responsive to determining that the first subject is an alternative representation of a live person, preventing access to a secure system.