Method of Reducing Visibility of Pulsed Illumination While Acquiring High Quality Imagery

• US 20120187838A1
• Filed: 01/26/2011
• Published: 07/26/2012
• Est. Priority Date: 06/26/2008
• Status: Active Grant

• Current Assignee: Global Rainmakers, Inc.
• Original Assignee: Global Rainmakers, Inc.
• Inventors: Hanna, Keith J.
• Granted Patent: US 9,965,672 B2
• Time in Patent Office: Days
• US Class Current: 315/76
• CPC Class Codes: G06V 10/141 Control of illumination
• CPC Class Codes: G06V 10/143 Sensing or illuminating at different wavelengths
• CPC Class Codes: G06V 40/166 using acquisition arrangements
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

A method of providing active illumination during biometry that utilizes pulsed lighting synchronized to frame acquisition. Two distinct illumination modalities are provided: the first maximizes the quality of images captured by the imaging system, and the second minimizes the overall illumination perceived by the user in combination with the first. The two modalities are provided substantially simultaneously. The first modality always includes a set of pulses synchronized with frame acquisition. The second modality may be either a second set of pulses not synchronized with frame acquisition or constant background illumination. The two modalities may be generated by two separate sources of illumination or by the same single illumination source. Adding the second modality to the first reduces user discomfort and the chances of an epileptic response as compared to using the first modality alone. The two modalities may have different wavelengths, pulse durations, or intensities.

Claims

1. A method of providing active illumination during biometry that utilizes pulsed lighting synchronized to imaging system frame acquisition, comprising the steps of:

a) providing a first illumination modality that maximizes the quality of images captured by the imaging system; and

b) providing a second illumination modality, substantially simultaneously as the first illumination modality, that, in combination with the first illumination modality, minimizes the overall illumination perceived by the user.

2. A method of providing active illumination during biometry according to claim 1, further comprising the step of providing a single illumination source, wherein:

said step a) further comprises the step of providing a first set of periodic illumination pulses synchronized with imaging system frame acquisition; and

said step b) further comprises the step of providing a second set of periodic illumination pulses not synchronized with imaging system frame acquisition.

3. A method of providing active illumination during biometry according to claim 2, wherein a frequency of a combination of the first and second sets of illumination pulses is greater than a response frequency for photosensitive epilepsy.

4. A method of providing active illumination during biometry according to claim 2, wherein a pulse rate of a combination of the first and second sets of illumination pulses falls substantially within the range of 2-10 times the pulse rate of the first set of pulses alone.

5. A method of providing active illumination during biometry according to claim 2, wherein the intensity of the second set of pulses is equal to or greater than the intensity of the first set.

6. A method of providing active illumination during biometry according to claim 1, further comprising the step of setting a frame acquisition rate of the imaging system to a maximum value.

7. A method of providing active illumination during biometry according to claim 1, wherein:

step a) provides the first illumination modality as a first set of periodic illumination pulses, and

step b) provides the second illumination modality as constant background illumination.

8. A method of providing active illumination during biometry according to claim 7, wherein the background illumination of the second modality is in the range of from at least 0.02 times, up to but not equal to, the average illumination of the pulses of the first illumination modality.

9. A method of providing active illumination during biometry according to claim 7, wherein step a) and step b) are both provided by the same single illumination source.

10. A method of providing active illumination during biometry according to claim 7, wherein step a) is performed by a first illumination source and step b) is performed by a second illumination source.

11. A method of providing active illumination during biometry according to claim 10, wherein a first wavelength of the light from the first illumination source is different from a second wavelength of the light of the second illumination source.

12. A method of providing active illumination during biometry according to claim 11, wherein the first wavelength is substantially in the range of 700-900 nm and the second wavelength is substantially in the range of 400-700 nm.

13. A method of providing active illumination during biometry according to claim 10, wherein the intensity of the light from the second illumination source is substantially 0.1-10 times the intensity of the light from the first illumination source.

14. A method of providing active illumination during biometry according to claim 1, wherein:

step a) further comprises the step of providing a first illumination source to generate a first set of periodic illumination pulses; and

step b) further comprises the step of providing a second illumination source to generate a second set of periodic illumination pulses having a substantially inverse waveform of the first set of pulses.

15. A method of providing active illumination during biometry according to claim 14, wherein a first wavelength of the light from the first illumination source is different from a second wavelength of the light of the second illumination source.

16. A method of providing active illumination during biometry according to claim 15, wherein the first wavelength is substantially in the range of 700-900 nm and the second wavelength is substantially in the range of 400-700 nm.

17. A method of providing active illumination during biometry according to claim 15, wherein the maximum distance between the first and second illumination sources is D=0.0006 R.

18. A method of providing active illumination during biometry according to claim 15, wherein the maximum distance between the first and second illumination sources is D=0.006 R.

19. A method of providing active illumination during biometry according to claim 1, wherein:

said step a) further comprises the step of providing a first set of periodic illumination pulses of a first duration and having a first intensity synchronized with imaging system frame acquisition;

said step b) further comprises the step of providing a second set of periodic illumination pulses not synchronized with imaging system frame acquisition, said second set of pulses having a second duration shorter than the first duration and a second intensity equal to or greater than the first intensity.

20. A method of providing active illumination during biometry according to claim 19, wherein the second pulses are 0.001 to 1 times the duration and 1 to 100 times the intensity of the first pulses.

21. A method according to claim 1, further comprising the steps of:

sensing the actual output of at least one of the first and second illumination modalities; and

adjusting the output of at least one of the first and second illumination modalities in response to the output sensed in the sensing step.

22. A method according to claim 21, further comprising the step of using the sensed output to minimize the difference in illumination between the first and second modalities of illumination.

23. A method of providing active illumination during the acquisition of high quality images of a person that utilizes pulsed lighting synchronized to imaging system frame acquisition, comprising the steps of:

a) providing a first illumination modality that maximizes the quality of images captured by the imaging system; and

b) providing a second illumination modality, substantially simultaneously as the first illumination modality, that, in combination with the first illumination modality, minimizes the overall illumination perceived by the user.