Methods and systems for image registration
View Patent ↗Aspects of the present invention are related to methods and systems for image processing, in particular, to methods and systems for computationally efficient and robust image alignment. Initially, larger image features may be used to approximate an alignment measurement. Results of the initial measurement may be used to narrow the search range used in conjunction with higher-resolution images in subsequent alignment measurements. The narrowed search range may insure that if the alignment measurement using the fine-detail images fails, then the measured results may have the accuracy as indicated by the prior, reduced-image-based measurement.
1. A method for aligning a test image and a reference image, said method comprising:
a) determining a first reduction factor associated with a first direction;
b) determining a second reduction factor associated with a second direction;
c) scaling the reference image according to the first reduction factor and the second reduction factor;
d) scaling the test image according to the first reduction factor and the second reduction factor;
e) determining a first alignment measurement between the test image and the reference image using the scaled test image and the scaled reference image;
f) adjusting the test image according to the first alignment measurement; and
g) determining a second alignment measurement between the test image and the reference image using the adjusted test image and the reference image;
wherein:
a) the first reduction factor is based on a first search range in the first direction; and
b) the second reduction factor is based on a second search range in the second direction;
and wherein:
a) the first reduction factor is calculated according to
⌊
(
3
2
FirstSearchRange
)
2
5
⌋
,
where FirstSearchRange denotes the first search range; and
b) the second reduction factor is calculated according to
⌊
(
3
2
SecondSearchRange
)
2
5
⌋
,
where SecondSearchRange denotes the second search range.
2. The method as described in claim 1 , wherein:
a) the first direction is a direction selected from the group consisting of vertical and horizontal; and
b) the second direction is the other, non-selected direction from the group consisting of vertical and horizontal.
3. The method as described in claim 1 further comprising adjusting the test image according to the second alignment measurement.
4. The method as described in claim 1 further comprising:
a) for the test image and the reference image, receiving a crude alignment measurement; and
b) wherein:
i) the scaling the test image further comprises adjusting the test image according to the crude alignment measurement; and
ii) the adjusting the test image according to the first alignment measurement further comprises adjusting the test image according to the crude alignment measurement.
5. The method as described in claim 1 , wherein the test image comprises a crudely aligned version of an image associated with the test image.
6. A method for aligning a test image and a reference image, said method comprising:
a) determining a first reduction factor associated with a first direction;
b) scaling, in the first direction, the reference image according to the first reduction factor;
c) scaling, in the first direction, the test image according to the first reduction factor;
d) determining a first-direction first alignment measurement, in the first direction, between the test image and the reference image using the first-direction scaled test image and the first-direction scaled reference image;
e) adjusting the test image according to the first-direction first alignment measurement; and
f) determining a first-direction second alignment measurement, in the first direction, between the test image and the reference image using the test image adjusted according to the first-direction first alignment measurement and the reference image;
further comprising:
a) determining a second reduction factor associated with a second direction;
b) scaling, in the second direction, the reference image according to the second reduction factor;
c) scaling, in the second direction, the test image according to the second reduction factor;
d) determining a second-direction first alignment measurement, in the second direction, between the test image and the reference image using the second-direction scaled test image and the second-direction scaled reference image;
e) adjusting the test image according to the second-direction first alignment measurement; and
f) determining a second-direction second alignment measurement, in the second direction, between the test image and the reference using the test image adjusted according to the second-direction first alignment measurement and the reference image;
wherein:
a) the first reduction factor is based on a first search range in the first direction; and
b) the second reduction factor is based on a second search range in the second direction,
and wherein:
a) the first reduction factor is calculated according to
⌊
(
3
2
FirstSearchRange
)
2
5
⌋
,
where FirstSearchRange denotes the first search range; and
b) the second reduction factor is calculated according to
⌊
(
3
2
SecondSearchRange
)
2
5
⌋
,
where SecondSearchRange denotes the second search range.
7. The method as described in claim 6 further comprising:
a) for the test image and the reference image, receiving a crude alignment measurement; and
b) wherein:
i) the scaling, in the first direction, the test image further comprises adjusting the test image according to the crude alignment measurement; and
ii) the adjusting the test image according to the first-direction first alignment further comprises adjusting the test image according to the crude alignment measurement.
8. The method as described in claim 6 , wherein the test image comprises a crudely aligned version of an image associated with the test image.
9. A method for aligning a test image and a reference image, said method comprising:
a) determining a first reduction factor associated with a first direction;
b) determining a second reduction factor associated with a second direction;
c) scaling the reference image according to the first reduction factor and the second reduction factor, thereby producing a first scaled reference image;
d) scaling the test image according to the first reduction factor and the second reduction factor, thereby producing a first scaled test image;
e) determining first alignment measurement between the test image and the reference image using the first scaled reference image and the first scaled test image;
f) adjusting the test image according to the first alignment measurement;
g) determining a third reduction factor associated with the first direction;
h) determining a fourth reduction factor associated with the second direction;
i) scaling the reference image according to the third reduction factor and the fourth reduction factor, thereby producing a second scaled reference image;
j) scaling the first-alignment-measurement adjusted test image according to the third reduction factor and the fourth reduction factor, thereby producing a scaled, first-adjusted test image;
k) determining a second alignment measurement between the test image and the reference image using the second scaled reference image and the scaled, first-adjusted test image;
l) adjusting the first-alignment-measure adjusted test image according to the second alignment measurement; and
m) determining a third alignment measurement between the test image and the reference image using the reference image and the second-alignment-measurement adjusted first- alignment-measurement adjusted test image.