Optics for an extended depth of field
View Patent ↗An optical imaging assembly having cylindrical symmetry, comprising a plurality of lenses having surfaces with curvatures and spacings between the surfaces, such that an optical image formed by the plurality of lenses has a defocus aberration coefficient greater than 0.1 at a focal plane of the assembly.
1. A method for forming an optical imaging assembly, comprising:
providing an aperture for the optical imaging assembly configured to collect a portion of optical radiation from an object;
providing an optical assembly configured to collect at least a subset of the portion of optical radiation, and comprising a set of at least three lenses, the optical assembly having substantially cylindrical symmetry with respect to a common optical axis;
arranging the set of at least three lenses to facilitate forming an optical image from a subset of the collected portion of optical radiation at a focal plane of the optical imaging assembly, the optical image comprising:
a modulation transfer function for spatial frequencies greater than 50 cycles per millimeter having at least one value smaller than or equal to about 0.35.
2. The method of claim 1 , wherein arranging the set of at least three lenses to facilitate forming the optical image, further comprises the optical image having a point spread function at least about 14 μm on the focal plane.
3. The method of claim 1 , further comprising providing an infra-red filter and positioning the infra-red filter between the set of at least three lenses and the focal plane.
4. The method of claim 1 , further comprising providing an image sensor substantially co-planar with the focal plane.
5. The method of claim 1 , further comprising arranging the set of at least three lenses to facilitate forming the optical image with a defocus aberration coefficient greater than about 0.1.
6. The method of claim 5 , further comprising providing a deconvolution engine for correcting at least a portion of image distortion of the optical image generated by the set of at least three lenses.
7. The method of claim 6 , further comprising providing a virtual phase plate in conjunction with the set of at least three lenses, the virtual phase plate having characteristics to generate the defocus aberration coefficient, the characteristics being substantially negatives of corresponding characteristics of the deconvolution engine for correcting at least the portion of the image distortion.
8. The method of claim 6 , further comprising arranging the set of at least three lenses to facilitate forming the optical image so that the modulation transfer function has a range of values for all objects from a far field to at least twenty centimeters from the optical assembly, the range of values between about 0.25 and about 0.40.
9. The method of claim 8 , wherein providing the deconvolution engine further comprises configuring the deconvolution engine to improve the image distortion for all objects from the far field to at least twenty centimeters from the optical assembly.
10. A method for forming an optical imaging assembly, including:
providing a plurality of lenses having cylindrical symmetry and surfaces with curvatures and spacings between the surfaces; and
arranging the lenses so that an optical image formed by the plurality of lenses has a defocus aberration coefficient greater than 0.1 at a focal plane of the assembly.
11. The method of claim 10 , further comprising arranging the lenses so that the optical image has a defocus aberration coefficient greater than about 0.6 and less than or equal to about 0.9 at the focal plane.
12. The method of claim 10 , further comprising arranging the lenses so that the optical image has a fifth order spherical aberration between about −0.2 and about −0.3.
13. The method of claim 10 , further comprising arranging the lenses so that the optical image has a seventh order spherical aberration that is about −0.5.
14. The method of claim 10 , further comprising arranging the lenses so that the optical image has a ninth order spherical aberration that is about zero.
15. The method of claim 10 , further comprising arranging the lenses so that the optical image subtends a field of view up to about thirty three degrees to an optical axis of the optical imaging assembly.
16. The method of claim 10 , further comprising arranging the lenses so that the optical image is a focused image of an object at a distance equal to or greater than about ten centimeters from the optical imaging assembly.
17. The method of claim 10 , further comprising arranging the lenses so that a modulation transfer function of the optical image is less than or equal to 0.35 for spatial frequencies greater than 50 cycles per millimeter.
18. The method of claim 10 , further comprising arranging the lenses so that the optical image has an extent of a point spread function equal to or greater than about fourteen micrometers at the focal plane.