Detect, reflect, validate

1. A method for detecting a visual marker comprising:

capturing a first image containing the visual marker at a first time T 1 under a first lighting condition;

performing a first image-based detection for the visual marker based on the first image, using a first detector, to produce a first set of results;

capturing a second image containing the visual marker at a second time T 2 under a second lighting condition different from the first lighting condition; and

based on the first set of results, performing a second image-based detection for the visual marker based on the second image, using a second detector different from the first detector, to produce a second set of results,

wherein the visual marker comprises a first material having a first reflective property in response to the first lighting condition and a second material having a second reflective property in response to the second lighting condition.

2. The method of claim 1 , wherein the second material overlays the first material.

3. The method of claim 1 , further comprising a step of activating one or more light sources while capturing one of the first and second images.

4. The method of claim 3 , wherein the one or more light sources comprise an infrared (IR) light source.

5. The method of claim 1 , wherein the first lighting condition and the second lighting condition correspond to two different intensities of light.

6. The method of claim 1 wherein the first lighting condition and the second lighting condition correspond to two different ranges of spectrum of light.

7. The method of claim 1 , wherein one of the first and second materials is an IR-reflective material.

8. The method of claim 1 , wherein one of the first and second materials is a retroreflective material.

9. The method of claim 1 , wherein performing the second image-based detection using the second image, based on the first set of results, comprises:

determining a restricted region of interest within the second image, based on the first set of results; and

performing the second image-based detection for the visual marker within the restricted region of interest within the second image.

10. The method of claim 1 , wherein performing the second image-based detection using the second image, based on the first set of results, comprises:

determining whether to perform the second image-based detection for the visual marker using the second image, based on the first set of results.

11. The method of claim 10 ,

wherein the determination of whether to perform the second image-based detection is made based on a detected size of the visual marker within the first image; and

wherein the second image-based detection is performed if the detected size of the visual marker within the first image is less than predetermined size.

12. The method of claim 1 , wherein performing the second image-based detection for the visual marker comprises:

performing the second image-based detection based on a measure of contrast between a first area of the visual marker associated with the first material having the first reflective property and a second area of the visual marker associated with the second material having the second reflective property within the second image.

13. The method of claim 1 , wherein the first image-based detection or second image-based detection is performed using a trained machine learning (ML) model.

14. The method of claim 1 , wherein the first image-based detection or second image-based detection is performed using a non-ML technique.

15. The method of claim 1 , wherein and the first image is captured using a sensor, and the second image is captured using the sensor.

16. The method of claim 1 , wherein the first image is captured using a first sensor, and the second image is captured using a second sensor.

17. The method of claim 1 , further comprising:

prior to performing the first image-based detection for the visual marker using the first image, detecting a reference object; and

wherein the first image-based detection for the visual marker within the first image is performed based on a known estimated position of the visual marker relative to the reference object.

18. An apparatus for detecting a visual marker comprising:

one or more sensors for capturing a first image containing the visual marker at a first time T 1 under a first lighting condition and capturing a second image containing the visual marker at a second time T 2 under a second lighting condition different from the first lighting condition;

a first detector for performing a first image-based detection for the visual marker based on the first image, to produce a first set of results; and

a second detector for performing, based on the first set of results, a second image-based detection for the visual marker based on the second image, to produce a second set of results, wherein the second detector is different from the first detector;

wherein the visual marker comprises a first material having a first reflective property in response to the first lighting condition and a second material having a second reflective property in response to the second lighting condition.

19. The apparatus of claim 18 , wherein the second material overlays the first material.

20. The apparatus of claim 18 , wherein one of the first and second materials is an IR-reflective material.

21. The apparatus of claim 18 , wherein the second detector is configured to perform the second image-based detection using the second image, based on the first set of results, by:

determining a restricted region of interest within the second image, based on the first set of results; and

performing the second image-based detection for the visual marker within the restricted region of interest within the second image.

22. The apparatus of claim 18 , wherein the second detector is configured to perform the second image-based detection using the second image, based on the first set of results, by:

determining whether to perform the second image-based detection for the visual marker using the second image, based on the first set of results.

23. The apparatus of claim 22 ,

wherein the determination of whether to perform the second image-based detection is made based on a detected size of the visual marker within the first image; and

wherein the second detector is configured to perform the second image-based detection if the detected size of the visual marker within the first image is less than predetermined size.

24. Computer readable medium having stored therein code for causing a processor to perform operations for detecting a visual marker comprising:

code for causing a first image containing the visual marker to be captured at a first time T 1 under a first lighting condition;

code for causing a first image-based detection for the visual marker based on the first image to be performed, using a first detector, to produce a first set of results;

code for causing a second image containing the visual marker to be captured at a second time T 2 under a second lighting condition different from the first lighting condition; and

code for causing a second image-based detection for the visual marker based on the first set of results to be performed, based on the second image, using a second detector different from the first detector, to produce a second set of results,

wherein the visual marker comprises a first material having a first reflective property in response to the first lighting condition and a second material having a second reflective property in response to the second lighting condition.

25. The computer readable medium of claim 24 , wherein the second material overlays the first material.

26. The computer readable medium of claim 24 , wherein one of the first and second materials is an IR-reflective material.

27. The computer readable medium of claim 24 , wherein the code for performing the second image-based detection using the second image, based on the first set of results, comprises:

code for determining a restricted region of interest within the second image, based on the first set of results; and

code for performing the second image-based detection for the visual marker within the restricted region of interest within the second image.

28. The computer readable medium of claim 24 , wherein the code for performing the second image-based detection using the second image, based on the first set of results, comprises:

code for determining whether to perform the second image-based detection for the visual marker using the second image, based on the first set of results.

29. The computer readable medium of claim 28 ,

wherein the determination of whether to perform the second image-based detection is made based on a detected size of the visual marker within the first image; and

wherein the second image-based detection is performed if the detected size of the visual marker within the first image is less than predetermined size.

30. A system for detecting a visual marker comprising:

means for capturing a first image containing the visual marker at a first time T 1 under a first lighting condition;

means for performing a first image-based detection for the visual marker based on the first image, using a first detector, to produce a first set of results;

means for capturing a second image containing the visual marker at a second time T 2 under a second lighting condition different from the first lighting condition; and

means for, based on the first set of results, performing a second image-based detection for the visual marker based on the second image, using a second detector different from the first detector, to produce a second set of results,

wherein the visual marker comprises a first material having a first reflective property in response to the first lighting condition and a second material having a second reflective property in response to the second lighting condition.