Range measurement using multiple coded apertures
A method of using an image capture device to identify range information for objects in a scene includes providing an image capture device having an image sensor, at least two coded apertures, and a lens; storing in a memory a set of blur parameters derived from range calibration data for each coded aperture; capturing images of the scene having a plurality of objects using each of the coded apertures; providing a set of deblurred images using the captured images from each coded aperture and each of the blur parameters from the stored set; and using the set of deblurred images to determine the range information for the objects in the scene.
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, at least two coded apertures having different spatial frequency responses, and a lens;
b) storing in a memory a set of blur parameters derived from range calibration data for each coded aperture;
c) capturing images of the scene having a plurality of objects using each of the coded apertures;
d) providing a set of deblurred images using the captured images from each coded aperture and each of the blur parameters from the stored set; 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 d) includes for each deblurred image
i) initializing a candidate deblurred image;
ii) determining a plurality of differential images representing differences between neighboring pixels in the candidate deblurred including a range of at least 1 or more pixels in size and including vertical, horizontal and diagonal directions;
iii) determining a combined differential image by combining the differential images;
iv) updating the candidate deblurred image responsive to the captured image, the blur kernel, the candidate deblurred image and the combined differential image; and
v) repeating steps i)-iv) until a convergence criterion is satisfied.
3. The method of claim 1 , wherein step c) includes capturing first and second image sequences, corresponding to the first and second coded apertures, respectively.
4. The method of claim 3 , wherein step e) includes determining range information for each image in the sequence.
5. The method of claim 4 , wherein step e) includes determining range information for a subset of images in the sequence.
6. The method of claim 4 , wherein the range information is used to identify stationary and moving objects in the scene.
7. The method of claim 6 , wherein the range information is used by the image capture device to track moving objects.
8. The method of claim 3 , 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.
9. The method of claim 8 , wherein step e) includes determining range information for the objects in the scene, responsive to the difference image.
10. The method of claim 1 , wherein step d) includes using a subset of blur parameters from the stored set.
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 a set of blur parameters for each coded aperture at each corresponding range value.
12. The method of claim 1 , wherein step b) includes storing a subset of blur parameters derived from calibration data at a set of range values, responsive to information provided by the image capture device.
13. The method of claim 1 , wherein step e) includes combining the deblurred images according to a spatial-frequency dependent weighting criterion.
14. The method of claim 1 , wherein step e) includes combining deblurred images resulting from blur parameters corresponding to each coded aperture within selected range intervals.
15. The method of claim 14 , further including combining the deblurred images according to a spatial-frequency dependent weighting criterion.
16. 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) at least two coded apertures having different spatial frequency responses;
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 kernel, 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.
17. 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, at least two coded apertures having different spatial frequency responses, and a lens;
b) storing in a memory a set of blur parameters derived from range calibration data for each coded aperture, 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 for each coded aperture at each corresponding range value, wherein the sets of blur parameters corresponding to each coded aperture are associated with overlapping range intervals;
c) capturing images of the scene having a plurality of objects using each of the coded apertures;
d) providing a set of deblurred images using the captured images from each coded aperture and each of the blur parameters from the stored set; and
e) using the set of deblurred images to determine the range information for the objects in the scene.
18. 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, at least two coded apertures having different spatial frequency responses, and a lens;
b) storing in a memory a set of blur parameters derived from range calibration data for each coded aperture, 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 for each coded aperture at each corresponding range value wherein the sets of blur parameters corresponding to each coded aperture are associated with non-overlapping range intervals;
c) capturing images of the scene having a plurality of objects using each of the coded apertures;
d) providing a set of deblurred images using the captured images from each coded aperture and each of the blur parameters from the stored set; and
e) using the set of deblurred images to determine the range information for the objects in the scene.