Systems and methods for efficiently capturing high-quality scans of multi-page documents with hand-held devices

1. A method of capturing a sequence of images of a multi-page printed document, performed by a handheld device with one or more processors, memory, and a digital image sensor, the method comprising:

monitoring a time sequence of preview images of a first printed page of the multi-page printed document, the preview images generated by the digital image sensor;

without user indication of when to capture an image, capturing a still image of the first printed page when a first quality metric of the preview images exceeds a first quality threshold;

repeating the monitoring and capturing of additional pages of the multi-page printed document until receiving indication from the user that capturing images is complete; and

in response to receiving indication from the user that capturing images is complete:

concatenating the captured still images into a single digital document; and

storing the single digital document.

2. The method of claim 1 , wherein capturing an image of a respective printed page further comprises notifying the user to turn the page after capturing the still image.

3. The method of claim 1 , wherein capturing an image of a respective printed page further comprises after capturing the still image:

evaluating at least a portion of the captured still image at full resolution according to a second quality metric;

when the second quality metric is below a second quality threshold, notifying the user that capture of the respective page will be repeated, and repeating the monitoring of preview images of the respective printed page.

4. The method of claim 1 , wherein capturing an image of a respective printed page further comprises after capturing the still image:

evaluating at least a portion of the captured still image at full resolution according to a second quality metric;

when the second quality metric is below a second quality threshold, repeating the monitoring of preview images of the respective printed page; and

when the second quality metric is at or above the second quality threshold, notifying the user the still image has been captured.

5. The method of claim 1 , further comprising:

evaluating each of the respective captured still images, and assigning a respective second quality score to each respective captured still image;

sorting the captured still images according to their assigned second quality scores; and

prompting the user to review the captured still images in the sorted order, and repeating the monitoring and capturing operations for images selected by the user, thereby replacing selected captured still images with higher quality captured images.

6. The method of claim 5 , wherein the evaluating, sorting, and prompting are in response to receiving the indication from the user that capturing images is complete.

7. The method of claim 1 , further comprising:

evaluating each of the respective captured still images, and assigning a respective second quality score to each respective captured still image;

identifying a set of captured still images whose corresponding second quality scores are below a second quality threshold; and

repeating the monitoring and capturing operations for each of the captured still images in the identified set, thereby replacing the captured still images in the identified set with higher quality captured images.

8. The method of claim 7 , wherein the evaluating, identifying, and repeating the monitoring and capturing operations for each of the captured still images in the identified set are in response to receiving the indication from the user that capturing images is complete.

9. The method of claim 1 , wherein the indication from the user comprises a button press on a user interface of the handheld device.

10. The method of claim 1 , wherein the indication from the user comprises a voice command from the user.

11. The method of claim 1 , further comprising:

determining that two or more captured still images correspond to a single printed page of the multi-page printed document;

selecting one of the captured still images corresponding to the single printed page; and

discarding all of the captured still images corresponding to the single printed page except the selected one.

12. The method of claim 11 , wherein the determining, selecting, and discarding are in response to receiving the indication from the user that capturing images is complete.

13. The method of claim 1 , further comprising:

receiving indication from the user that the multi-page printed document is a two-sided document; and

capturing still images of the multi-page printed document in an order not corresponding to the order of the pages in the multi-page printed document;

wherein concatenating the captured still images into a single digital document further comprises ordering the captured still images corresponding to the order of the pages in the multi-page printed document.

14. The method of claim 1 , wherein concatenating the captured still images into a single digital document further comprises ordering the captured still images based on the order in which the still images were captured.

15. The method of claim 1 , wherein monitoring preview images further comprises:

identifying four document edge lines in a first preview image;

determining whether there are any turning points for the first preview image inside a rectangle formed by the four document edge lines; and

when there are one or more turning points inside the rectangle, notifying the user of an image protrusion.

16. A system for capturing a sequence of images of a multi-page printed document, comprising:

one or more processors;

memory; and

one or more programs stored in the memory, the one or more programs comprising instructions for:

monitoring a time sequence of preview images of a first printed page of the multi-page printed document, the preview images generated by the digital image sensor;

capturing a still image of the first printed page when a first quality metric of the preview images exceeds a first quality threshold, executed without user indication of when to capture the still image;

repeating the monitoring and capturing of additional pages of the multi-page printed document until receiving indication from the user that capturing images is complete; and

responding to receiving indication from the user that capturing images is complete, including instructions for:

concatenating the captured still images into a single digital document; and

storing the single digital document.

17. A computer readable storage medium storing one or more programs configured for execution by a computer, the one or more programs comprising instructions for:

monitoring a time sequence of preview images of a first printed page of the multi-page printed document, the preview images generated by the digital image sensor;

capturing a still image of the first printed page when a first quality metric of the preview images exceeds a first quality threshold, executed without user indication of when to capture the still image;

repeating the monitoring and capturing of additional pages of the multi-page printed document until receiving indication from the user that capturing images is complete; and

responding to receiving indication from the user that capturing images is complete, including instructions for:

concatenating the captured still images into a single digital document; and

storing the single digital document.