Passive three-dimensional object authentication based on image sizing

Patent metadata

Field	Value
Publication number	US-11830284-B2
Application number	US-202117352375-A
Country	US
Kind code	B2
Filing date	Jun 21, 2021
Priority date	Jun 21, 2021
Publication date	Nov 28, 2023
Grant date	Nov 28, 2023

Abstract

Techniques are described for passive three-dimensional (3D) object authentication based on image sizing, such as for biometric facial recognition. For example, during a registration routine, an imaging system captures images of a registering user's face at multiple distances. The images can be processed to extract registration dimensions, including individual deterministic structural dimensions, dimensional relationships that are static over changes in imaging distance, and dimensional relationships that changes predictably over changes in imaging distance. During an authentication routine, the imaging system again captures authentication images of an authenticating user's face (purportedly the previously registered user) at some authentication imaging distance and processes the images to extract authentication dimensions. Expected and actual dimensional quantities are computed from the authentication and registration dimensions and are compared to determine whether the authenticating user's face appears to be authorized as previously registered and/or is a spoof.

First claim

What is claimed is:

1. A method for authentication of an authentication object based on passive imaging, the method comprising:
capturing a set of images of the authentication object using an imaging system located an authentication imaging distance away from a first deterministic structure of a plurality of deterministic structures of the authentication object that are visible in the set of images;
processing the set of images to measure at least a first authentication dimension of the first deterministic structure and a second authentication dimension of a second deterministic structure of the plurality of deterministic structures;
obtaining registration dimensions from a registration database acquired by measuring at least the first deterministic structure and the second deterministic structure during a prior registration process; computing the authentication imaging distance based on a relationship between the first authentication dimension and the registration dimensions, and computing an expected imaging distance for the second deterministic structure based on a relationship between the authentication imaging distance and the registration dimensions;
computing an authentication normalization factor as a ratio between the first and second authentication dimensions, and computing an expected normalization factor for the second deterministic structure at the expected imaging distance based on the registration dimensions and the authentication imaging distance; and
authenticating the authentication object based on comparing the authentication normalization factor with the expected normalization factor; wherein the authentication imaging distance is computed as a function of a focal characteristic of the imaging system and a ratio between a first registration dimension and the first authentication dimension, the first registration dimension acquired by measuring the first deterministic structure during the prior registration process.

2. The method of claim 1 , further comprising:
outputting a user-perceivable authentication result to indicate whether the authenticating results in granting or denying authentication.

3. The method of claim 1 , wherein the obtaining registration dimensions comprises obtaining, from the registration database, a first registration dimension acquired by measuring the first deterministic structure during the prior registration process, a second registration dimension acquired by measuring the second deterministic structure during the prior registration process, and a registration imaging distance delta between the first and second deterministic structures computed during the registration process.

4. The method of claim 3 , wherein the second registration dimension, the first authentication dimension, and the second authentication dimension are measured according to a unit dimension defined during the prior registration process based on the first registration dimension.

5. The method of claim 1 , wherein the expected imaging distance is computed for the second deterministic structure by adding the authentication imaging distance to a registration imaging distance delta, the registration imaging distance delta being a difference between the respective imaging distances from the imaging system to each of the first and second deterministic structures during the prior registration process.

6. The method of claim 1 , wherein the expected normalization factor for the second deterministic structure is computed as a function of a second registration dimension and a ratio between the authentication imaging distance and the expected imaging distance, the second registration dimension acquired by measuring the second deterministic structure during the prior registration process.

7. The method of claim 1 , wherein the capturing comprises capturing at least one of the set of images with the imaging system zoomed in on the authentication object to form the at least one of the set of images with increased depth resolution.

8. The method of claim 1 , wherein:
the plurality of deterministic structures comprises the first deterministic structure, and a plurality of other deterministic structures that includes the second deterministic structure;
the processing the set of images comprises processing the set of images to measure the first authentication dimension for the first deterministic structure and a respective other authentication dimension for each of the plurality of other deterministic structures;
the obtaining registration dimensions comprises obtaining registration dimensions acquired by measuring the first deterministic structure and the plurality of other deterministic structures during the prior registration process;
the computing the expected imaging distance comprises computing a respective expected imaging distance for each of the plurality of other deterministic structures;
the computing the authentication normalization factor comprises computing a respective authentication normalization factor for each of the plurality of other deterministic structures;
the computing the expected normalization factor comprises computing a respective expected normalization factor for each of the plurality of other deterministic structures at the respective expected imaging distance; and
the authenticating the authentication object is based on comparing a plurality of the respective authentication normalization factors with a corresponding plurality of the respective expected normalization factors.

9. The method of claim 8 , wherein:
at least a first of the plurality of other deterministic structures of the authentication object is a macro-structure; and
at least a second of the plurality of other deterministic structures of the authentication object is a micro-structure.

10. The method of claim 1 , wherein the authenticating the authentication object comprises both biometric verification and spoof detection based on at least a portion of the plurality of deterministic structures of the authentication object.

11. A system for authentication of an authentication object based on passive imaging, the system comprising:
a registration database having, stored thereon, a plurality of registration dimensions acquired by measuring a plurality of deterministic structures of an authentication object during a prior registration process;
an imaging subsystem to capture a set of images of the authentication object while the authentication object is an authentication imaging distance away from a first deterministic structure of the plurality of deterministic structures; and
a control and processing module having one or more processors and a memory having, stored thereon, a set of instructions which, when executed, cause the one or more processors to perform steps comprising:
processing the set of images to measure at least a first authentication dimension of the first deterministic structure and a second authentication dimension of a second deterministic structure of the plurality of deterministic structures;
computing the authentication imaging distance based on a relationship between the first authentication dimension and the registration dimensions; computing an expected imaging distance for the second deterministic structure based on a relationship between the authentication imaging distance and the registration dimensions;
computing an authentication normalization factor as a ratio between the first and second authentication dimensions;
computing an expected normalization factor for the second deterministic structure at the expected imaging distance based on the registration dimensions and the authentication imaging distance; and

authenticating the authentication object based

Assignees

• Shenzhen Goodix Tech Co Ltd

Inventors

• He Yi
• Pi Bo

Classifications

• G06V40/166 Primary

  using acquisition arrangements · CPC title

• G06F21/32 Primary

  using biometric data, e.g. fingerprints, iris scans or voiceprints · CPC title

• G06V20/64

  Three-dimensional [3D] objects · CPC title

• G06V40/165

  using facial parts and geometric relationships · CPC title

• G06V40/172

  Classification, e.g. identification · CPC title