Systems and methods for locating a retroreflective object in a digital image
Systems and methods are disclosed for locating a retroreflective object in a digital image and/or identifying a feature of the retroreflective object in the digital image. In certain environmental conditions, e.g. on a sunny day, or when the retroreflective material is damaged or soiled, it may be more challenging to locate the retroreflective object in the digital image and/or to identify a feature of the object in the digital image. The systems and methods disclosed herein may be particularly suited for object location and/or feature identification in situations in which there is a strong source of ambient light (e.g. on a sunny day) and/or when the retroreflective material on the object is damaged or soiled.
1. A system comprising:
a first image acquisition device to acquire at least a first image with light emitted from an illuminator;
a second image acquisition device to acquire at least a second image without or with less of the light emitted from the illuminator;
a memory to store at least the first image and the second image;
a processor to:
generate a compound image from the first image from the first image acquisition device and the second image from the second image acquisition device;
align content of the first image and the second image to at least account for different physical locations of the first image acquisition device and the second image acquisition device prior to generating the compound image; and
locate an object in the compound image.
2. The system of claim 1 , wherein the object has a retroreflective material.
3. The system of claim 1 , wherein the processor is to align the content of the first image and the second image by obtaining at least one displacement vector representing displacement of the content between the first image and the second image, and applying the at least one displacement vector to pixels of either the first image or the second image.
4. The system of claim 3 , wherein the at least one displacement vector represents static displacement of the content between the first image and the second image.
5. The system of claim 3 , wherein the at least one displacement vector represents static and dynamic displacement of the content between the first image and the second image, and wherein obtaining the at least one displacement vector comprises computing the at least one displacement vector.
6. The system of claim 3 , wherein the at least one displacement vector is a plurality of displacement vectors, each one of the plurality of displacement vectors corresponds to a respective section in the first and second image.
7. The system of claim 1 , wherein the processor is to align content of the first image and the second image based on static displacement of the content between the first image and the second image.
8. The system of claim 7 , wherein the processor is to align content of the first image and the second image based on the static displacement and dynamic displacement of the content between the first image and the second image.
9. The system of claim 1 , further comprising the illuminator, and wherein the processor is to control the first image acquisition device to acquire the first image and control the illuminator to emit the light in order to synchronize light emission by the illuminator with acquisition of the first image.
10. The system of claim 1 , wherein the processor is to generate the compound image from the first image and the second image by subtracting the second image from the first image.
11. The system of claim 1 , wherein the processor is further to identify a feature of the object in the compound image.
12. The system of claim 11 , wherein the object is a license plate, and the feature is a vehicle registration identifier on the license plate.
13. The system of claim 1 , wherein the object is a license plate.
14. The system of claim 1 , wherein the first image acquisition device is a first infrared camera, the second image acquisition device is a second infrared camera, the first image is a first monochrome image, and the second image is a second monochrome image.
15. A method comprising:
activating an illuminator to emit light, and acquiring a first image from a first image acquisition device with light emitted from the illuminator;
acquiring a second image from a second image acquisition device without or with less of the light emitted from the illuminator;
generating a compound image from the first image from the first image acquisition device and the second image from the second image acquisition device;
aligning content of the first image and the second image to at least account for different physical locations of the first image acquisition device and the second image acquisition device prior to generating the compound image; and
locating an object in the compound image.
16. The method of claim 15 , wherein the object has a retroreflective material.
17. The method of claim 15 , wherein the aligning comprises obtaining at least one displacement vector representing displacement of the content between the first image and the second image, and applying the at least one displacement vector to pixels of either the first image or the second image.
18. The method of claim 17 , wherein the at least one displacement vector represents static displacement of the content between the first image and the second image.
19. The method of claim 17 , wherein the at least one displacement vector represents static and dynamic displacement of the content between the first image and the second image, and wherein obtaining the at least one displacement vector comprises computing the at least one displacement vector.
20. The method of claim 17 , wherein the at least one displacement vector is a plurality of displacement vectors, each one of the plurality of displacement vectors corresponds to a respective section in the first and second image.
21. The method of claim 15 , wherein aligning the content of the first image and the second image comprises aligning the content of the first image and the second image based on static displacement of the content between the first image and the second image.
22. The method of claim 21 , wherein aligning the content of the first image and the second image comprises aligning the content of the first image and the second image based on the static displacement and dynamic displacement of the content between the first image and the second image.
23. The method of claim 15 , comprising controlling the first image acquisition device to acquire the first image and controlling the illuminator to emit the light in order to synchronize light emission by the illuminator with acquisition of the first image.
24. The method of claim 15 , wherein generating the compound image comprises subtracting the second image from the first image.
25. A non-transitory processor-readable medium having stored thereon instructions that, when executed by one or more processors, cause the one or more processors to perform operations comprising:
receiving, from a first image acquisition device, a first image that was acquired by the first image acquisition device with light emitted from an illuminator;
receiving, from a second image acquisition device, a second image that was acquired by the second image acquisition device without or with less of the light emitted from the illuminator;
generating a compound image from the first image from the first image acquisition device and the second image from the second image acquisition device;
aligning content of the first image and the second image to at least account for different physical locations of the first image acquisition device and the second image acquisition device prior to generating the compound image; and
locating an object in the compound image.
26. The non-transitory processor-readable medium of claim 25 , wherein the object has a retroreflective material.
27. The non-transitory processor-readable medium of claim 25 , wherein the instructions, when executed, cause the one or more processors to perform the aligning of the content of the first image and the second image by performing operations including: obtaining at least one displacement vector representing displacement of the content between the first image and the second image, and applying the at least one displacement vector to pixels of either the first image or the second image.
28. The non-transitory processor-readable medium of claim 27 , wherein the at least one displacement vector represents static displacement of the content between the first image and the second image.
29. The non-transitory processor-readable medium of claim 27 , wherein the at least one displacement vector represents static and dynamic displacement of the content between the first image and the second image, and wherein the obtaining the at least one displacement vector comprises computing the at least one displacement vector.