Controlling an exposure time for digital cameras
View Patent ↗Various methods, apparatuses, and systems in which a digital photography device includes a global shutter to control exposure time, a sensor array, and a flash illumination are described. The global shutter is in the optical path of light going to the sensor. The flash illumination generates a pulsed illumination. The shutter speed of the global shutter during a pre-flash illumination substantially matches the shutter speed during the flash illumination during the taking of a picture using the flash illumination based on the global shutter receiving a trigger signal from a controller.
1. A digital photography device, comprising:
a global shutter to control exposure time;
a sensor array, wherein the global shutter is in an optical path of light going to the sensor array; and
a flash to generate a pulsed illumination, wherein the shutter speed of the global shutter during a pre-flash illumination is timed to substantially match the shutter speed during the flash illumination when a picture is taken using the flash illumination based on the global shutter receiving a trigger signal from a controller.
2. The digital photography device of claim 1 , wherein the controller to control an amount of light being exposed to the sensor array by triggering the global shutter during an ambient light condition.
3. The digital photography device of claim 2 , wherein the controller to use a ratio of the illumination level between before and during the pre-flash illumination to determine a proper power level to be applied to the flash during the picture.
4. The digital photography device of claim 1 , wherein the shutter speed during the pre-flash illumination substantially matches the shutter speed during the flash illumination by being within two times the shutter speed during the flash illumination.
5. The digital photography device of claim 1 , wherein the shutter speed before and during the pre-flash illumination substantially matches the shutter speed during the flash illumination by being within a factor of two times the shutter speed during the flash illumination.
6. The digital photography device of claim 1 , wherein the controller to adjust the power of the flash illumination to set an exposure time of the picture within a predefined range of illumination, so that the sensor array is within its optimum operating range based on an illumination level measured at least in part during the pre-flash illumination.
7. The digital photography device of claim 1 , wherein the controller to measure an illumination level both during an ambient condition and during the flash illumination from the sensor array.
8. The digital photography device of claim 1 , wherein the controller to trigger the global shutter to measure an ambient illumination level in the sensor array before the pre-flash illumination and then to store the ambient illumination data.
9. The digital photography device of claim 8 , wherein the controller to trigger the global shutter during the pre-flash illumination to measure a pre-flash illumination level in the sensor array and then to store the pre-flash illumination data.
10. The digital photography device of claim 9 , wherein the controller to trigger the global shutter during the flash illumination to measure a flash illumination level in the sensor array to control the sensor array's exposure to the photographic effects of ambient light and then to store the flash illumination data.
11. The digital photography device of claim 1 , wherein the global shutter to screen light from a perimeter area of the sensor array that is less than half a total area of the sensor array before and during the pre-flash illumination.
12. The digital photography device of claim 1 , wherein the sensor array is a complementary metal-oxide semiconductor sensor to implement a rolling shutter timing mechanism.
13. The digital photography device of claim 1 , wherein the global shutter is a mechanical shutter.
14. The digital photography device of claim 1 , wherein the digital photography device is one of a digital camera, a one-time use digital camera, or a cellular phone operable to take digital pictures.
15. The digital photography device of claim 14 , wherein the one-time use digital camera cooperates with an external processing unit; and the external processing unit receives the sensor array's data and then performs image processing operations on the data to convert the data to a formatted graphics file of a captured digital image.
16. A method, comprising:
tracking an amount of light being exposed to a sensor array in a digital photography device at a first time period, a second time period, and a third time period; and
transitioning a global shutter between an open state and a closed state just before and after the second and the third time period with the shutter speed during the second time period substantially matching the shutter speed during the third time period.
17. The method of claim 16 , further comprising:
determining if a flash illumination is required to set an exposure level of a picture to be within an optimum operating range of the sensor array based on the amount of light being exposed to the sensor array during the first time period.
18. The method of claim 16 , further comprising:
firing a pre-flash illumination if the flash illumination is determined to be required.
19. The method of claim 16 , further comprising:
determining an amount of additional illumination needed to set an exposure level of a picture to be within the optimum range based on the amount of light being exposed to the sensor array during the first and second time periods.
20. The method of claim 16 , further comprising:
firing a flash illumination with a power level based on the determination of additional illumination needed to set the exposure level within the optimum range.
21. The method of claim 16 , further comprising:
processing an amount of light exposed to pixels of the sensor array with a unit external to the digital photography device to generate a file representing a digital image.
22. The method of claim 16 , wherein the transitioning of a global shutter just before and after each time period has substantially the same shutter speed for the first, second, and third time periods.
23. An apparatus, comprising:
means for tracking an amount of light being exposed to a sensor array in a digital photography device at a first time period, a second time period, and a third time period; and
means for transitioning a global shutter between an open state and a closed state just before and after the second and the third time period with the shutter speed during the second time period substantially matching the shutter speed during the third time period.
24. The apparatus of claim 23 , further comprising:
means for determining if flash illumination is required to set the exposure level within an optimum operating range of the sensory array based on the amount of light being exposed to the sensor array during the first time period.
25. The apparatus of claim 23 , further comprising:
means for firing a pre-flash illumination if flash illumination is required.
26. The apparatus of claim 23 , further comprising:
means for determining the amount of additional illumination needed to set the exposure level within the optimum range based on the amount of light being exposed to the sensor array during the first and second time periods.
27. The apparatus of claim 23 , further comprising:
means for firing a flash illumination with a power level based on the determination of additional illumination needed to set the exposure level within the optimum range.
28. The apparatus of claim 23 , further comprising:
means for processing an amount of light exposed to pixels of the sensor array to generate a file representing a digital image.
29. The apparatus of claim 23 , wherein the transitioning of a global shutter just before and after each time period has substantially the same shutter speed for the first, second, and third time periods.