Embedding data on objects using surface modulation
Methods and apparatus are disclosed for embedding static information (such as serial numbers, etc.) on objects by modifying their exterior shape slightly, dubbed surface modulation. Data is embedded when the object is created and can then be read using readers with the appropriate resolution. According to one example of the disclosed technology, a method of embedding data expressed as a binary sequence onto an object surface includes establishing a coordinate system over an object surface, computing a transform of the coordinate system to a frequency domain, mapping the binary sequence to an integer value, replacing the highest frequency coefficient of the transform with the integer value, computing an inverse of the transform, producing a vector expressed in the coordinate system, and fabricating at least a portion of the object surface according to the vector.
1. A method of embedding data expressed as a binary sequence onto an object surface, the method comprising:
establishing a coordinate system over an object surface;
computing a discrete transform of the coordinate system to a frequency domain;
mapping the binary sequence to an integer value;
replacing one or more frequency coefficients of the discrete transform with the integer value;
computing an inverse of the transform, producing a vector expressed in the coordinate system; and
fabricating at least a portion of the object surface according to the vector.
2. The method of claim 1 , wherein the coordinate system is a one-dimensional or a two-dimensional coordinate system.
3. The method of claim 1 , wherein the one or more frequency coefficients is the highest frequency coefficient of the transform.
4. The method of claim 1 , wherein the discrete transform is a discrete cosine transform or discrete wavelet transform.
5. The method of claim 1 , wherein the discrete transform is a discrete sine transform, a discrete Hartley transform, a Chirplet transform, a Hankel transform, a Chebyshev transform, or a Hadamard transform.
6. The method of claim 1 , wherein the fabricating comprises using a 3-D printer, a laser etcher, or an array of transducers connected to a mold.
7. The method of claim 1 , wherein the vector is a one-dimensional or a two-dimensional vector.
8. An article of manufacture that is manufactured by performing the method of claim 1 , wherein the article is a vehicle component, integrated circuit, integrated circuit package, a firearm, or another manufactured object.
9. A method of decoding data stored on an object having an object surface, the method comprising:
scanning a surface of the object to determine a vector of surface measurements;
computing a discrete transform of the vector, producing a series of coefficients;
scaling one or more frequency coefficients of the series of coefficients to produce an integer value; and
mapping the integer value to a binary sequence.
10. The method of claim 9 , further comprising comparing the binary sequence to a database to identify the object.
11. The method of claim 9 , wherein the one or more frequency coefficients is the highest frequency coefficient of the series of coefficients.
12. The method of claim 9 , further comprising, prior to the scanning, manufacturing the object surface according to the vector.
13. The method of claim 9 , wherein the discrete transform is a discrete cosine transform or a discrete wavelet transform.
14. The method of claim 9 , wherein the scanning is performed using a laser or terahertz scanner.
15. The method of claim 9 , further comprising searching for the binary sequence in a database and based on the searching, identifying the object.
16. The method of claim 9 , further comprising:
prior to the scanning:
establishing a coordinate system over the surface of the object;
computing a discrete transform of the coordinate system to a frequency domain;
mapping the binary sequence to an integer value;
replacing one or more frequency coefficients of the discrete transform with the integer value;
computing an inverse of the discrete transform, producing an encoding vector expressed in the coordinate system; and
fabricating at least a portion of the object surface according to the encoding vector.
17. The method of claim 9 , wherein the surface of the object is not fabricated according to a vector.
18. The method of claim 17 , wherein the surface of the object has height variations that can be used to generate a unique binary sequence for use as a signature identifying the object.
19. One or more computer-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform the method of claim 9 .
20. An apparatus, comprising:
a processor;
memory;
a scanning device coupled to the processor, the scanning device operable to generate a vector of data by measuring the surface of an object; and
one or more computer-readable storage media storing computer-readable instructions that when executed by a computer, cause the computer to perform the method of claim 9 .
21. An article of manufacture, comprising:
an object having a surface, the object surface being encoded with by varying the height and/or depth of the object surface according to a method, the method comprising:
establishing a coordinate system over an object surface;
computing a discrete transform of the coordinate system to a frequency domain;
mapping a binary sequence to one or more encoding values;
replacing one or more frequency coefficients of the discrete transform with the encoding values;
computing an inverse of the discrete transform, producing a vector expressed in the coordinate system; and
fabricating at least a portion of the object surface according to the vector.
22. The article of manufacture of claim 21 , wherein the fabricating the object surface uses a laser, a transducer in communication with the object surface, or a 3-D printer.
23. The article of manufacture of claim 21 , wherein the method further comprises:
selecting a number of coefficient values N to use for the transform based on an amount of distortion induced in the transform relative to the wavelength of a reader to be used to read data embedded in the object surface according to the vector.
24. The article of manufacture of claim 21 , wherein the method further comprises:
selecting spacing of discrete points within the coordinate system based at least in part on one or more of the following: a database of x-y coordinates, information density, noise immunity, damage, or wear, in an anticipated environment in which the object will be subjected.