Light-field imaging based on tilt-aberration
A method, imaging system and computer program product for obtaining a transverse phase gradient of a wave field from at least a first and a second wavefield intensity map includes the steps of; capturing at a first incoherent tilt aberration the first wave field intensity map of a target at a first degree of incoherent tilt aberration, using a filter positioned between a source of electromagnetic radiation and an electromagnetic radiation detector capturing said first wave field intensity map; capturing at a second and different incoherent tilt aberration said second wave field intensity map of said target at a second degree of incoherent tilt aberration, using a filter positioned between a source of electromagnetic radiation and an electromagnetic radiation detector capturing the second wave field intensity map; determining the transverse phase gradient on the basis of at least a difference of logarithms of wavefield intensity maps divided by the magnitude of the difference between the first incoherent tilt aberration and the second incoherent tilt aberration.
1 . A method for obtaining a transverse phase gradient of a wave field from at least a first wavefield intensity map and a second wave field intensity map, said method comprising the steps of:
capturing at a first incoherent tilt aberration said first wave field intensity map of a target, using a first filter having an attenuation profile with a continuous derivative positioned between a source of electromagnetic radiation and an electromagnetic radiation detector capturing said first wave field intensity map,
capturing at a second incoherent tilt aberration said second wave field intensity map of said target, using a second filter having an attenuation profile with a continuous derivative positioned between a source of electromagnetic radiation and an electromagnetic radiation detector capturing said second wave field intensity map, wherein said second incoherent tilt aberration is different from said first incoherent tilt aberration,
determining said transverse phase gradient on the basis of at least a difference of logarithms of wavefield intensity maps divided by the magnitude of the difference between said first incoherent tilt aberration and said second incoherent tilt aberration,
wherein said difference of logarithms of wavefield intensity maps is a difference between a logarithm of an intensity of said first wave field intensity map and a logarithm of an intensity of said second wave field intensity map.
2 . The method according to claim 1 , wherein said difference between said first incoherent tilt aberration and said second incoherent tilt aberration is achieved by geometrically changing one or more of said source of electromagnetic radiation, said target, and said first filter and/or said second filter.
3 . The method according to claim 2 , wherein said geometrically changing comprises changing one or more of angle of irradiation of said target, transverse displacement of said first filter and/or said second filter, and transverse displacement of said target.
4 . The method according to claim 1 , wherein said source of electromagnetic radiation used in capturing said first wavefield intensity map is a first source of electromagnetic radiation, wherein said source of electromagnetic radiation used in capturing said second wavefield intensity map is a second source of electromagnetic radiation, and wherein said second source of electromagnetic radiation is displaced with respect to said first source of electromagnetic radiation.
5 . The method according to claim 1 , wherein said first filter and/or said second filter is a gaussian filter.
6 . The method according to claim 1 , wherein said first filter and/or said second filter is positioned in between said target and said electromagnetic radiation detector.
7 . The method according to claim 1 , wherein said first filter and said second filter are the same filter.
8 . The method according to claim 1 , wherein said first filter and said second filter are different filters.
9 . The method according to claim 1 , wherein said step of retrieving said phase gradient involves using the following term
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wherein I 1 (x 1 , y 1 ) is an intensity of said first wave field intensity map at a position (x 1 , y 1 ),
wherein I 2 (x 1 , y 1 ) is an intensity of said second wave field intensity map at a position (x 1 , y 1 ),
and wherein |τ 12 | is said magnitude of said difference between said first tilt and said second tilt.
10 . The method according to claim 9 , wherein said intensity I 1 and said intensity I 2 are representative of intensities of a corresponding pixel in said first wave field intensity map and said second wave field intensity maps.
11 . The method according to claim 1 , wherein said electromagnetic radiation detector comprises a camera.
12 . The method according to claim 1 , wherein said electromagnetic radiation detector used for capturing said first wave field intensity map and said electromagnetic radiation detector used for capturing said second wave field intensity map are the same electromagnetic radiation detector.
13 . The method according to claim 1 , wherein said attenuation profile of said first and second filter has a variable continuous derivative.
14 . The method according to claim 1 , wherein said attenuation profile of said first and second filter has a constant continuous derivative.
15 . The method according to claim 1 , wherein the method is executed by a computer processor of an imaging system.
16 . Use of the method according to claim 1 for contrast enhancement and/or digital refocusing.
17 . An imaging system comprising:
a source of electromagnetic radiation;
an electromagnetic radiation detector;
a first and a second filters;
a computer processor; and
a memory containing computer-implemented instructions that when carried out by said computer processor executes the steps;
capturing at a first incoherent tilt aberration a first wave field intensity map of a target, using said first filter having an attenuation profile with a continuous derivative positioned between said source of electromagnetic radiation and said electromagnetic radiation detector capturing said first wave field intensity map,
capturing at a second incoherent tilt aberration a second wave field intensity map of said target, using said second filter having an attenuation profile with a continuous derivative positioned between a source of electromagnetic radiation and an electromagnetic radiation detector capturing said second wave field intensity map, wherein said second incoherent tilt aberration is different from said first incoherent tilt aberration,
determining said transverse phase gradient on the basis of at least a difference of logarithms of wavefield intensity maps divided by the magnitude of the difference between said first incoherent tilt aberration and said second incoherent tilt aberration,
wherein said difference of logarithms of wavefield intensity maps is a difference between a logarithm of an intensity of said first wave field intensity map and a logarithm of an intensity of said second wave field intensity map
wherein said imaging system is configured to be adjustable between a first degree of tilt and a second degree of tilt.
18 . Use of the imaging system according to claim 17 for contrast enhancement and/or digital refocusing.
19 . The imaging system according to claim 17 , wherein said first and second filters have an attenuation profile having a variable continuous derivative.
20 . The imaging system according to claim 17 , wherein said first and second filters have an attenuation profile having a constant continuous derivative.