Methods for capturing and reading out images from an image sensor
View Patent ↗Multiple images are captured where the exposure times for some of the images overlap and the images are spatially overlapped. Charge packets are transferred from one or more portions of pixels after particular integration periods, thereby enabling the portion or portions of pixels to begin another integration period while one or more other portions of pixels continue to integrate charge. Charge packets may be binned during readout of the images from the image sensor. Comparison of two or more images having different lengths of overlapping or non-overlapping exposure periods provides motion information. The multiple images can then be aligned to compensate for motion between the images and assembled into a combined image with an improved signal to noise ratio and reduced motion blur.
1. A method for capturing images with an image sensor that includes a plurality of pixels each having an photosensitive area, vertical charge coupled devices (CCDs) each comprising a plurality of charge storage elements positioned adjacent to a respective column of pixels, and a transfer mechanism for transferring charge packets from each photosensitive area to a respective charge storage element, the method comprising:
beginning light integration for all of the pixels, wherein the photosensitive areas accumulate charge packets;
transferring charge packets from a first portion of pixels to respective charge storage elements in the vertical CCDs at a first time, wherein the charge packets from the first portion of pixels have a first integration period;
transferring charge packets from a second portion of pixels to respective charge storage elements in the vertical CCDs at a second time that is different from the first time, wherein the charge packets from the second portion of pixels have a second integration period that is different from the first integration period;
ending light integration for all of the pixels;
reading out the charge packets from the vertical CCDs;
transferring charge packets from the first and second portions of pixels to respective charge storage elements in the vertical CCDs, wherein the charge packets from the first portion of pixels have a third integration period and the charge packets from the second portion of pixels have a fourth integration period that is different from the third integration period; and
reading out the charge packets from the vertical CCDs.
2. The method of claim 1 , further comprising resetting all of the photosensitive areas in the image sensor.
3. The method of claim 1 , wherein the sum of the first and third integration periods substantially equals the sum of the second and fourth integration periods.
4. The method of claim 1 , wherein beginning light integration for all of the pixels comprises opening a mechanical shutter.
5. The method of claim 4 , wherein ending light integration for all of the pixels comprises closing the mechanical shutter.
6. The method of claim 1 , wherein transferring charge packets from the first portion of pixels to respective charge storage elements in the vertical CCDs at the first time comprises transferring charge packets from odd numbered lines of pixels to respective charge storage elements in the vertical CCDs at the first time, wherein the charge packets from the odd numbered lines of pixels have the first integration period.
7. The method of claim 6 , wherein transferring charge packets from the second portion of pixels to respective charge storage elements in the vertical CCDs at the second time that is different from the first time comprises transferring charge packets from even numbered lines of pixels to respective charge storage elements in the vertical CCDs at the second time that is different from the first time, wherein the charge packets from the even numbered lines of pixels have the second integration period that is different from the first integration period.
8. The method of claim 1 , wherein the first portion of pixels comprises single non-adjacent lines of pixels and the second portion of pixels comprises single non-adjacent lines of pixels.
9. The method of claim 1 , wherein the first portion of pixels comprises multiple adjacent lines of pixels and the second portion of pixels comprises multiple adjacent lines of pixels.
10. The method of claim 9 , wherein the first and second portions of pixels alternate with respect to each other.
11. The method of claim 1 , wherein the charge storage elements to which the charge packets from the first portion of pixels are transferred are different from the charge storage elements to which the charge packets from the second portion of pixels are transferred.
12. The method of claim 1 , wherein each charge storage element in the VCCDs is associated with only a single pixel.
13. The method of claim 1 , wherein beginning light integration for all of the pixels comprises performing an electronic shutter operation.
14. The method of claim 1 , wherein each pixel comprises a color filter element associated therewith.
15. The method of claim 1 , wherein the charge packets having the first and second integration periods are read out of the vertical CCDs after the third and fourth integration periods.
16. The method of claim 1 , wherein the first integration period is different from at least one of the third or fourth integration periods.
17. The method of claim 1 , wherein the second integration period is different from at least one of the third or fourth integration periods.