Coded aperture imaging system and method
An optical system includes a spatial encoding arrangement for generating spatially encoded light with an initial spatial distribution; a coded aperture defining a mask pattern based on the initial spatial distribution of the spatially encoded light; and—an image sensor. The spatial encoding arrangement—directs the spatially encoded light onto the object, and the object reflects at least a portion of the spatially encoded light to form reflected light. The reflected light is directed through the coded aperture to form spatially decoded light. The spatially decoded light is directed onto the image sensor to form an image thereon, and the image sensor detects the image. The spatial encoding arrangement includes optical emitters spatially arranged, defining the initial spatial pattern of the spatially encoded light. The mask pattern is the inverse of the initial spatial pattern of the spatially encoded light defined by the spatial arrangement of the optical emitters.
1. An optical system for imaging an object, the optical system comprising:
a spatial encoding arrangement for generating spatially encoded light with an initial spatial distribution;
a coded aperture defining a mask pattern which is based on the initial spatial distribution of the spatially encoded light; and
an image sensor,
wherein the optical system is configured such that, in use, the spatial encoding arrangement directs the spatially encoded light onto the object so that the object reflects at least a portion of the spatially encoded light to form reflected light, the reflected light is directed through the coded aperture to form spatially decoded light, the spatially decoded light is directed onto the image sensor so as to form an image thereon, and the image sensor detects the image, and
wherein the spatial encoding arrangement comprises a plurality of optical emitters, wherein the plurality of optical emitters are spatially arranged so as to define the initial spatial pattern of the spatially encoded light, and wherein the mask pattern defined by the coded aperture is the inverse of the initial spatial pattern of the spatially encoded light defined by the spatial arrangement of the plurality of optical emitters.
2. The optical system as claimed in claim 1 , wherein the image detected by the image sensor comprises at least one of:
an image of the object;
a sharp or focused image of the object;
a blurred image of the object;
a scaled image of the object; or a product of a scaled image of the object with a function which is independent of the mask pattern defined by the coded aperture.
3. The optical system as claimed in claim 1 , wherein the mask pattern comprises a binary mask pattern and/or wherein the coded aperture comprises a plurality of opaque regions and a plurality of transparent regions or apertures which together define the mask pattern.
4. The optical system as claimed in claim 1 , wherein the coded aperture is diffractive and/or wherein the coded aperture comprises a phase mask.
5. The optical system as claimed in claim 1 , wherein the mask pattern is configured such that an auto-correlation of the mask pattern is equal to, or resembles, a Kronecker delta function δ which includes a central peak or lobe, but which includes no secondary peaks or side-lobes, or which includes a central peak or lobe and one or more secondary peaks or side-lobes which have an amplitude which is less than 1/10 an amplitude of the central peak or lobe, which is less than 1/100 an amplitude of the central peak or lobe, or which is less than 1/1000 an amplitude of the central peak or lobe.
6. The optical system as claimed in claim 1 , wherein the mask pattern is a Uniformly Redundant Array (URA) mask pattern or a Modified Uniformly Redundant Array (MURA) mask pattern.
7. The optical system as claimed in claim 1 , wherein the coded aperture is reconfigurable, and wherein the coded aperture is formed from, or comprises, an LCD array.
8. The optical system as claimed in claim 1 , wherein at least one of:
the optical system is configured to reject or block ambient light reflected from the object;
the optical system comprises an optical filter in front of the image sensor for rejecting or blocking ambient light reflected from the object;
the image sensor is configured to detect infrared light;
the image sensor is configured to have a lower sensitivity to visible light and a higher sensitivity to infrared light; or
the spatially encoded light and the spatially decoded light both comprise, or are formed from, infrared light, the image sensor is configured to detect infrared light, and the optical system comprises an optical filter in front of the image sensor for rejecting or blocking visible light and for transmitting infrared light.
9. The optical system as claimed in claim 1 , wherein at least one of:
each optical emitter comprises a Lambertian optical emitter or a non-Lambertian optical emitter;
each optical emitter comprises an LED; or
each optical emitter is configured to emit infrared light.
10. The optical system as claimed in claim 1 , wherein each optical emitter of the plurality of optical emitters is operable independently of the one or more other optical emitters of the plurality of optical emitters.
11. The optical system as claimed in claim 1 , wherein the one or more optical emitters and the image sensor are co-planar, for example and wherein the one or more optical emitters and the image sensor are mounted or formed on the same substrate.
12. The optical system as claimed in claim 1 , wherein each optical emitter of the plurality of optical emitters absorbs or blocks the reflected light so that each optical emitter of the plurality of optical emitters defines a corresponding opaque or blocking region of the coded aperture and, optionally, aperture, and wherein each optical emitter of the plurality of optical emitters is mounted, or formed, on a substrate which is transparent to the light emitted by the plurality of optical emitters.
13. The optical system as claimed in claim 1 , wherein the spatial encoding arrangement comprises a plurality of lens elements, wherein each lens element is aligned in front of a corresponding optical emitter so as to at least partially focus or collimate light emitted by the corresponding optical emitter.
14. An electronic device comprising the optical system as claimed in any preceding claim , for example claim 1 , wherein the electronic device comprises a mobile electronic device, wherein the mobile electronic device comprises a user interface accessible by way of a display or a touchscreen, wherein the one or more optical emitters and the image sensor are located behind the user interface and the object is located in front of the user interface.
15. An optical system for imaging an object, the optical system comprising:
a spatial encoding arrangement for generating spatially encoded light with an initial spatial distribution;
a coded aperture defining a mask pattern which is based on the initial spatial distribution of the spatially encoded light; and
an image sensor,
wherein the optical system is configured such that, in use, the spatial encoding arrangement directs the spatially encoded light onto the object so that the object reflects at least a portion of the spatially encoded light to form reflected light, the reflected light is directed through the coded aperture to form spatially decoded light, the spatially decoded light is directed onto the image sensor so as to form an image thereon, and the image sensor detects the image,
wherein the spatial encoding arrangement comprises the coded aperture, and wherein the optical system is configured such that, in use, the one or more optical emitters emit light which passes through the coded aperture to form the spatially encoded light such that the initial spatial pattern of the spatially encoded light is defined by the mask pattern of the coded aperture.
16. A method for imaging an object, the method comprising:
directing spatially encoded light with an initial spatial distribution onto an object so that the object reflects at least a portion of the spatially encoded light to form reflected light;
directing the reflected light through a coded aperture to form spatially decoded light, wherein the coded aperture defines a mask pattern which is based on the initial spatial distribution of the spatially encoded light; and
directing the spatially decoded light onto an image sensor, wherein the spatially decoded light forms an image on the image sensor and the image sensor detects the image, and
wherein the initial spatial pattern of the spatially encoded light is defined by a spatial arrangement of a plurality of optical emitters, and wherein the mask pattern defined by the coded aperture is the inverse of the initial spatial pattern of the spatially encoded light defined by the spatial arrangement of the plurality of optical emitters.