RANGE MEASUREMENT USING A CODED APERTURE
A method of using an image capture device to identify range information includes providing an image capture device having an image sensor, coded aperture, and lens; storing in memory a set of blur parameters derived from range calibration data; and capturing an image having a plurality of objects. The method further includes providing a set of deblurred images using the capture image and each of the blur parameters from the stored set by, initializing a candidate deblurred image; determining a plurality of differential images representing differences between neighboring pixels in the candidate deblurred image; determining a combined differential image by combining the differential images; updating the candidate deblurred image responsive to the captured image, the blur parameters, the candidate deblurred image and the combined differential image; and repeating these steps until a convergence criterion is satisfied. Finally, the set of deblurred images are used to determine the range information.
1 . A method of using an image capture device to identify range information for objects in a scene, comprising:
a) providing an image capture device having an image sensor, a coded aperture, and a lens;
b) storing in a memory a set of blur parameters derived from range calibration data;
c) capturing an image of the scene having a plurality of objects;
d) providing a set of deblurred images using the capture image and each of the blur parameters from the stored set by,
i) initializing a candidate deblurred image;
ii) determining a plurality of differential images representing differences between neighboring pixels in the candidate deblurred image;
iii) determining a combined differential image by combining the differential images;
iv) updating the candidate deblurred image responsive to the captured image, the blur parameters, the candidate deblurred image and the combined differential image; and
v) repeating steps i)-iv) until a convergence criterion is satisfied; and
e) using the set of deblurred images to determine the range information for the objects in the scene.
2 . The method of claim 1 , wherein step c) includes capturing a sequence of digital images.
3 . The method of claim 2 , wherein step e) includes determining range information for each image in the sequence.
4 . The method of claim 2 , wherein step e) includes determining range information for a subset of images in the sequence.
5 . The method of claim 3 , wherein the range information is used to identify stationary and moving objects in the scene.
6 . The method of claim 5 , wherein the range information is used by the image capture device to track moving objects.
7 . The method of claim 2 , wherein the step of initializing a candidate deblurred image includes:
a) determining a difference image between the current and previous image in the image sequence; and
b) initializing a candidate deblurred image responsive to the difference image.
8 . The method of claim 7 , wherein step e) includes determining range information for the objects in the scene, responsive to the difference image.
9 . The method of claim 1 , wherein step d) includes using a subset of blur parameters from the stored set.
10 . The method of claim 1 , wherein step b) includes using a set of blur parameters derived from calibration data at a set of range values, such that there is a set of blur parameters associated with each corresponding range value.
11 . The method of claim 1 , wherein step b) includes using a set of blur parameters derived from calibration data at a set of range values, such that there is not a set of blur parameters for at least one range value.
12 . The method of claim 1 , wherein step b) includes using blur parameters computed from images captured with the coded aperture and a point light source at a series of range values.
13 . The method of claim 1 , wherein step e) includes combining deblurred images resulting from blur parameters corresponding to range values within a selected interval.
14 . The method of claim 13 , further including combining the deblurred images according to a spatial-frequency dependent weighting criterion.
15 . A digital camera system comprising:
a) an image sensor for capturing one or more images of a scene;
b) a lens for imaging the scene onto the image sensor;
c) a coded aperture;
d) a processor-accessible memory for storing a set of blur parameters derived from range calibration data; and
e) a data processing system for providing a set of deblurred images using captured images and each of the blur parameters from the stored set by,
i) initializing a candidate deblurred image;
ii) determining a plurality of differential images representing differences between neighboring pixels in the candidate deblurred image;
iii) determining a combined differential image by combining the differential images;
iv) updating the candidate deblurred image responsive to the captured image, the blur parameters, the candidate deblurred image and the combined differential image;
v) repeating steps i)-iv) until a convergence criterion is satisfied; and
vi) using the set of deblurred images to determine the range information for the objects in the scene.