Noncircular aperture imaging system
Various technologies pertaining to an imaging system with a noncircular aperture are described herein. An imaging objective with a noncircular aperture and an anamorphic lens is used to capture a plurality of image frames of a scene. Each image frame is captured at a different rotational orientation of the imaging objective with respect to the scene. Each image frame has a non-uniform spatial resolution. A composite image of the scene is generated based upon the image frames. The composite image comprises a first region that has a spatial resolution that is approximately the same as a spatial resolution of an image generated using a circular objective with a diameter equal to the largest dimension of the noncircular aperture, and a second region with a lower spatial resolution.
1. An imaging system, comprising:
an imaging objective comprising:
a first optical element having a noncircular aperture;
an anamorphic optical system configured to receive light from the first optical element, wherein the anamorphic optical system increases a field of view of the imaging objective; and
an image processor that generates a composite image of a scene based upon light received by the imaging objective at a plurality of different times, wherein the imaging objective has a different rotational orientation with respect to the scene at each of the different times, wherein the composite image comprises a first region and a second region, the second region having a higher spatial resolution than the first region.
2. The imaging system of claim 1 , wherein the image processor generates a plurality of image frames of the scene, wherein each image frame in the plurality of image frames is based upon the light received by the objective at a respective time in the different times, the composite image generated based upon the plurality of image frames.
3. The imaging system of claim 2 , wherein each image frame in the plurality of image frames has a first spatial resolution in a first direction and a second spatial resolution in a second direction, the second spatial resolution greater than the first spatial resolution.
4. The imaging system of claim 3 , wherein the spatial resolution of the second region of the composite image is greater than the first spatial resolution.
5. The imaging system of claim 4 , wherein the spatial resolution of the second region of the composite image is approximately equal to the second spatial resolution.
6. The imaging system of claim 2 , wherein the composite image is generated based upon the plurality of image frames using super-resolution reconstruction.
7. The imaging system of claim 2 , wherein the plurality of image frames comprises between 10 and 200 image frames.
8. The imaging system of claim 1 , wherein the anamorphic optical system comprises a Bravais system.
9. The imaging system of claim 8 , wherein the Bravais system comprises:
a negative lens that receives light from the first optical element; and
a positive lens that receives light from the negative lens.
10. The imaging system of claim 1 , the anamorphic optical system configured to increase the field of view of the objective in a direction of a smallest dimension of the noncircular aperture.
11. The imaging system of claim 1 , wherein the aperture has a length and a width that is orthogonal to the length, wherein the length is between 2 and 25 times greater than the width.
12. A method, comprising:
generating a plurality of image frames of a scene based upon light received by way of an imaging objective at a plurality of different times, the imaging objective having a noncircular aperture, the imaging objective comprising an anamorphic optical system, the anamorphic optical system configured to increase a field of view of the imaging objective in a first direction, wherein each image frame in the plurality of image frames has a first spatial resolution in the first direction and a second spatial resolution in a second direction, the second spatial resolution greater than the first spatial resolution; and
generating a composite image based upon the plurality of image frames, wherein the composite image comprises a first region and a second region, wherein a spatial resolution of the second region is higher than a spatial resolution of the first region.
13. The method of claim 12 , wherein the imaging objective has a different rotational orientation with respect to the scene at each of the different times.
14. The method of claim 12 , wherein the spatial resolution of the second region is approximately equal to the second spatial resolution.
15. The method of claim 12 , wherein generating the composite image based upon the plurality of image frames comprises generating the composite image based upon the plurality of image frames using a super-resolution algorithm.
16. The method of claim 15 , wherein the first region of the composite image has the first spatial resolution and the second region of the composite image has the second spatial resolution.
17. The method of claim 12 , wherein generating the composite image based upon the plurality of image frames comprises:
computing a plurality of Fourier transforms, each Fourier transform in the plurality of Fourier transforms corresponding to a respective image frame;
constructing a composite Fourier transform based upon the Fourier transforms; and
generating an inverse transform of the composite Fourier transform, wherein the inverse transform comprises the composite image.
18. The method of claim 17 , wherein constructing the composite Fourier transform based upon the Fourier transforms comprises:
identifying frequency components of the Fourier transforms that correspond to a high-resolution direction of at least one image frame in the plurality of image frames; and
computing a sum of the identified frequency components, wherein the sum of the identified frequency components comprises the composite Fourier transform.
19. The method of claim 17 , wherein generating the composite image based upon the plurality of image frames further comprises weighting each of the Fourier transforms in the plurality of Fourier transforms based upon a point-spread function of the aperture, wherein constructing the composite Fourier transform is based upon the weighted Fourier transforms.
20. An imaging system, comprising:
an imaging objective comprising:
a first optical element with a noncircular aperture, the noncircular aperture having a minor axis and a major axis; and
an anamorphic lens configured to receive light from the first optical element, wherein the anamorphic lens extends a field of view of the imaging objective in a direction of the minor axis; and
an image processor configured to perform the following acts:
generating a plurality of image frames of a scene based upon light received by way of the imaging objective, each image frame in the plurality of image frames corresponding to a different respective rotational orientation of the imaging objective, wherein each image frame in the plurality of image frames has a highest resolution in a direction of the major axis of the noncircular aperture; and
generating a composite image of the scene based upon the plurality of image frames, wherein the composite image of the scene comprises a first region that has a substantially uniform spatial resolution that is approximately equal to the highest resolution of the plurality of image frames and a second region that has a lower spatial resolution than the first region.