Extended depth of field using a multi-focal length lens with a controlled range of spherical aberration and a centrally obscured aperture

An extended depth of field imaging system comprising:

• a multifocal imaging subsystem designed as a combination of an ideal imaging component and a spherical aberration component that balances in and out of focus effects through a range of object distances;
• an intermediate image detecting device for detecting images formed by the imaging subsystem exhibiting balanced in and out of focus effects through the range of object distances;
• and
• a computer processing device for calculating a recovered image having an extended depth of field based on a correction of the balanced in and out of focus effects through the range of object distances.

A method of designing a multifocal imaging subsystem as a part of an integrated computational imaging subsystem comprising steps of:

• designing a first overall component of the multifocal imaging subsystem as an ideal imaging component for imaging an object at a given object distance;
• designing a second overall component of the multifocal imaging subsystem as a spherical aberrator for balancing in and out of focus effects through a range of object distances;
• combining the first and second components of the multifocal imaging subsystem to produce an intermediate image that is purposefully blurred and the second component of the multifocal imaging subsystem contributes an aspherical aberration that is the dominant feature of the purposeful blur;
• and
• arranging for supplying information concerning the intermediate image and the purposeful blur to a digital processing system for producing a recovered image having an extended depth of field.

An integrated computational imaging system for producing images having an extended depth of field comprising:

• a multifocal imaging subsystem for producing an intermediate image of an object combining an ideal overall imaging component and a prescribed overall aberration component for purposefully blurring the intermediate image;
• a central obscuration of the multifocal imaging subsystem that renders point spread functions of object points produced with the purposeful blurring more uniform over a range of object distances;
• and
• a digital processing subsystem for deblurring the intermediate image produced by the multifocal imaging subsystem and for calculating a recovered image having an extended depth of field.

An integrated computational imaging system for producing images having an extended depth of field comprising:

• a multifocal imaging subsystem for producing an intermediate image that is purposefully blurred in such a way that renders point spread functions of object points more uniform over a range of object distances than corresponding point spread functions produced without the purposeful blur;
• an average of the point spread functions having a central peak;
• a central obscuration of the multifocal imaging subsystem providing for narrowing the central peak of the average point spread function among the object points;
• and
• a digital processing subsystem for deblurring the intermediate image produced by the multifocal imaging subsystem and for calculating a recovered image based on the average point spread function over a range of focal depths.

A method of designing a multifocal lens system for extended depth of field imaging comprising the steps of

• modifying an ideal lens design by incorporating into the lens design an amount of third order spherical aberration;
• testing performance of the modified lens design for imaging over a range of focal depths;
• and
• adjusting the amount of the third order spherical aberration for producing point spread functions that vary less over the extended depth of field.

A method of designing an integrated computational imaging system for producing images having an extended depth of field comprising steps of:

• formulating an imaging system having an aberration component dominated by a third order spherical aberration for producing a blurred intermediate image;
• and
• determining an amount of the third order spherical aberration that reduces variations among impulse responses over the extended depth of field;
• calculating an impulse response that departs from an arithmetic average of the impulse responses over the extended depth of field to unevenly weight the impulse responses over the extended depth of field;
• and
• incorporating the calculated impulse response in a digital processing algorithm for deblurring the intermediate image produced by the multifocal imaging subsystem and for calculating a recovered image having an extended depth of field.

A method of recovering an image based on an intermediate image, comprising steps of:

• accessing an intermediate image;
• and
• performing an iterative digital deconvolution of the intermediate image using a maximum entropy algorithm including the sub-steps of:
• estimating a new image containing a combination of directional images;
• and
• altering the directional images using a metric parameter to speed convergence toward a recovered image while avoiding points of stagnation.

An iterative digital deconvolution method for image processing comprising steps of:

• calculating a succession of estimated images of an object based on a starting image and combination of directional images;
• inputting a metric parameter that modifies the directional images;
• evaluating the estimated images modified according to the metric parameter against a criterion of entropy maximization and a statistical noise parameter to choose a closer estimate of the object;
• and
• outputting an enhanced image of the object over the starting image.