Automatically capturing focused images obtained through unguided manual focus adjustment
In an image capture period, light from a scene is received through an optical system free of automatic focusing components. A sequence of focal values is produced from image data produced during the image capture period. One or more target focus criteria are determined from one or more of the focal values produced during a calibration portion of the image capture period. An image of the scene is automatically captured in response to a determination that one or more of the focal values produced after the calibration portion of the image capture period satisfies the target focus criteria.
1 . An image capture method, comprising:
receiving light from a scene through an optical system free of automatic focusing components in an image capture period during which a focus of the optical system is adjusted manually in relation to the scene;
generating image data from the light received during the image capture period;
producing a sequence of focal values from the image data during the image capture period;
determining one or more target focus criteria from one or more of the focal values produced during a calibration portion of the image capture period; and
automatically capturing an image of the scene in response to a determination that one or more of the focal values produced after the calibration portion of the image capture period satisfies the one or more target focus criteria.
2 . The method of claim 1 , wherein the optical system has a fixed focal length, and further comprising manually adjusting the focus of the optical system by physically moving the optical system toward and away from the scene during the image capture period.
3 . The method of claim 1 , wherein the producing comprises generating contrast focal values measuring contrast in the image data.
4 . The method of claim 3 , wherein the determining comprises identifying a target one of the contrast focal values generated during the calibration portion of the image capture period.
5 . The method of claim 4 , wherein the capturing comprises automatically capturing the image of the scene in response to a determination that one of the contrast focal values generated after the calibration portion of the image capture period is at least as high as the identified target focal value.
6 . The method of claim 4 , wherein the identified target contrast focal value corresponds to a maximal one of the focal contrast values generated during the calibration portion of the image capture period.
7 . The method of claim 1 , wherein the determining comprises identifying the calibration portion of the image capture period based on user input defining the boundaries of the calibration portion.
8 . The method of claim 1 , wherein the determining comprises identifying the calibration portion of the image capture period by identifying when successive ones of the focal values produced before a transition time predominantly vary in accordance with respective gradients of a first polarity and successive ones of the focal values produced after the transition time predominantly vary in accordance with respective gradients of a second polarity opposite the first polarity.
9 . The method of claim 1 , wherein the capturing comprises comparing the focal values produced after the calibration portion of the image capture period with the one or more target focus criteria.
10 . The method of claim 1 , wherein the capturing comprises automatically capturing the image of the scene independently of any user input command.
11 . An image capture system, comprising:
an optical system free of automatic focusing components and operable to receive light from a scene;
an image sensor operable to generate image data in response to light received from the optical system; and
a processing system operable to
produce a sequence of focal values from the image data generated by the image sensor during an image capture period,
determine one or more target focus criteria from one or more of the focal values produced during a calibration portion of the image capture period, and
cause an image of the scene to be captured in response to a determination that one or more of the focal values produced after the calibration portion of the image capture period satisfies the one or more target focus criteria.
12 . The system of claim 11 , wherein the optical system has a fixed focal length.
13 . The system of claim 11 , wherein the processing system is operable to generate contrast focal values measuring contrast in the image data.
14 . The system of claim 13 , wherein the processing system is operable to identify a target one of the contrast focal values generated during the calibration portion of the image capture period.
15 . The system of claim 14 , wherein the processing system is operable to cause the image of the scene to be captured in response to a determination that one of the contrast focal values generated after the calibration portion of the image capture period is at least as high as the identified target focal value.
16 . The system of claim 14 , wherein the identified target contrast focal value corresponds to a maximal one of the focal contrast values generated during the calibration portion of the image capture period.
17 . The system of claim 11 , wherein the processing system is operable to identify the calibration portion of the image capture period based on user input defining the boundaries of the calibration portion.
18 . The system of claim 11 , wherein the processing system is operable to identify the calibration portion of the image capture period by identifying when successive ones of the focal values produced before a transition time predominantly vary in accordance with respective gradients of a first polarity and successive ones of the focal values produced after the transition time predominantly vary in accordance with respective gradients of a second polarity opposite the first polarity.
19 . The system of claim 11 , wherein the processing system is operable to compare the focal values produced after the calibration portion of the image capture period with the one or more target focus criteria.
20 . The system of claim 11 , wherein the processing system is operable to cause the image of the scene to be automatically captured independently of any user input command.