Lensless imaging system including phase mask
Provided is an imaging system including a phase mask including a phase modulation meta surface coded with an image reconstruction phase function configured to reconstruct an image, the image reconstruction phase function being obtained by adding a first phase function corresponding to a lens phase to a second phase function which is a random function, and an image sensor configured to convert light, transmitted through the phase mask from an object, into an electrical signal.
1 . An imaging system comprising:
a phase mask comprising a phase modulation meta surface coded with an image reconstruction phase function configured to reconstruct an image, the image reconstruction phase function being obtained by adding a first phase function corresponding to a lens phase to a second phase function which is a random function; and
an image sensor configured to convert light, transmitted through the phase mask from an object, into an electrical signal,
wherein the second phase function is a function having spatially correlated randomness having a coherence length as a parameter.
2 . The imaging system of claim 1 , further comprising an image reconstruction processor configured to execute a reconstruction algorithm corresponding to the image reconstruction phase function and process a signal from the image sensor.
3 . The imaging system of claim 1 , wherein an imaging lens is not provided between the object and the image sensor.
4 . The imaging system of claim 1 , wherein a point spread function by the phase modulation meta surface includes a speckle pattern formed within a certain range from a center portion of the phase modulation meta surface.
5 . The imaging system of claim 4 , wherein the coherence length of the second phase function is set such that a diameter of the certain range is less than or equal to 30% of a lens effective diameter represented by the first phase function.
6 . The imaging system of claim 1 , wherein the second phase function is a phase function corresponding to trainable coefficients.
7 . The imaging system of claim 1 , wherein the first phase function is a phase function corresponding to a convex lens.
8 . The imaging system of claim 1 , wherein the first phase function is a phase function corresponding to a micro lens array.
9 . The imaging system of claim 1 , wherein a distance between the phase mask and the image sensor is less than a focal length of a lens having the first phase function.
10 . The imaging system of claim 1 , wherein a distance between the phase mask and the image sensor is less than or equal to a half of a focal length of a lens having the first phase function.
11 . The imaging system of claim 1 , wherein the phase modulation meta surface comprises a plurality of nano-structures, and
wherein a shape of the plurality of nano-structures and a size of the plurality of nano-structures are determined based on the image reconstruction phase function.
12 . The imaging system of claim 11 , wherein the phase mask further comprises a substrate,
wherein the plurality of nano-structures are on the substrate.
13 . The imaging system of claim 12 , wherein the substrate includes a material transparent to long-wave infrared (LWIR).
14 . The imaging system of claim 11 , further comprising a cover layer comprising:
a first surface facing the image sensor; and
a second surface opposite to the first surface,
wherein the plurality of nano-structures are on the first surface.
15 . The imaging system of claim 14 , further comprising a filter layer on the second surface.
16 . The imaging system of claim 15 , wherein the filter layer is configured to transmit long-wave infrared (LWIR) and block light of other wavelength bands.
17 . The imaging system of claim 15 , wherein the filter layer is configured to transmit light of a certain wavelength band, and
wherein the cover layer includes a material transparent to the light of the certain wavelength band.
18 . An electronic device comprising:
an imaging system comprising:
a phase mask comprising a phase modulation meta surface coded with an image reconstruction phase function configured to reconstruct an image, the image reconstruction phase function being obtained by adding a first phase function corresponding to a lens phase to a second phase function which is a random function; and
an image sensor configured to convert light, transmitted through the phase mask from an object, into an electrical signal,
wherein the second phase function is a function having spatially correlated randomness having a coherence length as a parameter.
19 . The electronic device of claim 18 , wherein the phase modulation meta surface comprises a plurality of nano-structures, and
wherein a shape of the plurality of nano-structures and a size of the plurality of nano-structures are determined based on the image reconstruction phase function.