Method of obtaining a digital image
Devices, systems and methods are described. A method includes driving a first light source to generate a visible light pulse having a first intensity for a first duration to illuminate a scene. An image sensor is used to record a visible-spectrum image of the scene illuminated by the first light pulse. A second light source is driven to generate a second light pulse having a second intensity that exceeds the first intensity by at least 100% for a second duration that is at most 10% of the first duration to illuminate the scene during the first duration. An image sensor is used to record a monochrome image of the scene illuminated by the second light pulse. Image processing is performed on a visible-spectrum image and the monochrome image to obtain the digital image of the scene.
1. A method of obtaining a digital image of a scene, the method comprising:
driving a first light source using a first drive current having a first current density of about 1.0 A/mm2 to generate a visible light pulse having a first intensity for a first duration to illuminate the scene, the first duration being at least a sensor integration time;
using an image sensor to record a visible-spectrum image of the scene illuminated by the first light pulse;
driving a second light source using a second drive current having a second current density of more than about 1.5 A/mm2 to generate a second light pulse having a second intensity that exceeds the first intensity by at least about 100% for a second duration that is at most about 10% of the first duration to illuminate the scene during the first duration, the second duration being at most about 5.0 ms;
using an image sensor to record a monochrome image of the scene illuminated by the second light pulse, the image sensor used to record the monochrome image being the same or different than the image sensor used to record the visible-spectrum image; and
performing image processing on the visible-spectrum image and the monochrome image to obtain the digital image of the scene.
2. The method according to claim 1 , wherein the image processing is performed on a sequence of visible-spectrum images and monochrome images recorded with respective light pulses.
3. The method according to claim 1 , wherein the image processing comprises identifying a common image region corresponding to an imaged subject present in the visible-spectrum image and the monochrome image.
4. The method according to claim 1 , further comprising identifying a motion blur image region in the visible-spectrum image.
5. The method according to claim 4 , further comprising correcting color values in at least the motion blur image region.
6. A system comprising:
a visible-spectrum light source configured to emit visible-spectrum light in a visible spectrum;
a second light source that is configured to emit at least one type of light selected from the visible-spectrum light in the visible-spectrum and infrared-spectrum light in an infrared-spectrum;
a driver configured to provide a first drive current having a first current density of about 1.0 A/mm2 to a first light source to generate a first light pulse having a first light intensity over a first duration and to provide a second drive current having a second current density of more than about 1.5 A/mm2 to the second light source to generate a second light pulse having a second light intensity that exceeds the first light intensity by at least about 100% over a second duration that is at most about 10% of the first duration, the first light pulse being a visible-spectrum light pulse, the first duration being at least a sensor integration time, the second duration being at most about 5.0 MS;
at least one image sensor having pixels that are sensitive to at least the visible-spectrum light; and
an image processing unit configured to combine information from a visible-spectrum image and a monochrome image to obtain a digital image of a scene.
7. The system according to claim 6 , wherein the second light source comprises one or more light-emitting diodes configured to emit the infrared-spectrum light.
8. The system according to claim 6 , wherein the second light source comprises one or more vertical cavity surface-emitting laser diodes.
9. The system according to claim 6 , wherein the at least one image sensor comprises a single image sensor that comprises pixels that are sensitive to the visible-spectrum and pixels that are sensitive to the infrared-spectrum.
10. The system according to claim 9 , wherein the single image sensor further comprises a filter that is at least partially transmissive to the infrared-spectrum.
11. The system according to claim 6 , wherein the at least one image sensor comprises two image sensors, each comprising only pixels that are sensitive to the visible-spectrum.
12. The system according to claim 6 , wherein the at least one image sensor comprises two image sensors, and a first one of the two image sensors comprises pixels that are sensitive to the visible-spectrum, and a second one of the two image sensors comprises pixels that are sensitive to the infrared-spectrum.
13. The system according to claim 12 , wherein the first one of the two image sensors comprises a filter that is transmissive only in the visible-spectrum, and the second one of the two image sensors comprises a filter that is transmissive only in the infrared-spectrum.
14. The system according to claim 6 , wherein the sensor integration time is approximately 50 ms.
15. The system according to claim 6 , wherein the second duration is at most about 1.0 ms.
16. A wireless device comprising:
a camera flash comprising:
a visible-spectrum light source configured to emit visible-spectrum light in a visible spectrum,
a second light source that is configured to emit at least one type of light selected from the visible-spectrum light in the visible-spectrum and infrared-spectrum light in an infrared-spectrum, and
a driver configured to provide a first drive current having a first current density of about 1.0 A/mm2 to a first light source to generate a first light pulse having a first light intensity over a first duration and to provide a second drive current having a second current density of more than about 1.5 A/mm2 to the second light source to generate a second light pulse having a second light intensity that exceeds the first light intensity by at least about 100% over a second duration that is at most about 10% of the first duration, the first light pulse being a visible-spectrum light pulse, the first duration being at least a sensor integration time, the second duration being at most about 5.0 ms;
a camera comprising at least one image sensor having pixels that are sensitive to at least the visible-spectrum light; and
an image processing unit configured to combine information from a visible-spectrum image and a monochrome image to obtain a digital image of a scene.
17. The device of claim 16 , wherein the device is a smartphone.
18. The device of claim 16 , wherein at least one of the first light source and the second light source comprises one or more light-emitting diodes.
19. The device of claim 16 , wherein:
the pixels comprise visible-spectrum pixels that are sensitive to the visible-spectrum light and infrared sensitive pixels that are sensitive to the infrared-spectrum,
the infrared sensitive pixels are about 25% of a total number of pixels in the at least one image sensor, and
the infrared sensitive pixels are distributed between the visible-spectrum pixels.