Depth of field in an imaging system

Abstract

A method is described of capturing an image. The method comprising the steps of: exposing an image sensor to radiation from a first part of the electromagnetic spectrum using a first aperture and to radiation from a second part of the spectrum using a second aperture having a different size than the first aperture; and, forming an image on the basis of first image data generated by the radiation from the first part of the spectrum and second image data generated by radiation from the second part of the spectrum.

1 . A method of capturing an image, the method comprising the steps of:
 exposing an image sensor to radiation from a first part of the electromagnetic spectrum using at least a first aperture and to radiation from a second part of the spectrum using at least a second aperture having a different size than the first aperture;   forming an image on the basis of first image data generated by the radiation from the first part of the spectrum and second image data generated by radiation from the second part of the spectrum.   
     
     
         2 . The method according to  claim 1 , wherein the image sensor is simultaneously exposed by radiation from the first and second aperture. 
     
     
         3 . The method according to  claim 1 , the method further comprising the steps of:
 subjecting the first image data to a high pass filter;   adding the filtered high frequency components of the first image data to the second image data.   
     
     
         4 . The method according to  claim 1 , wherein the first aperture is adapted to control exposure of radiation from a first part of the spectrum, preferably a part in the infra-red spectrum, and wherein the second aperture is adapted to control exposure to radiation from a second part of the spectrum, preferably a part in the visible spectrum. 
     
     
         5 . The method according to  claim 1 , wherein the first aperture is formed by an opening in a substrate or by partly covering the substrate with a filter reflecting radiation in a first part of the spectrum and transmitting radiation in a second part of the spectrum. 
     
     
         6 . The method according to  claim 1 , wherein the second aperture is formed by partly covering a substrate with a filter reflecting radiation in a first part of the spectrum, preferably the infra-red part, and transmitting radiation in a second part of the spectrum, preferably visible part. 
     
     
         7 . The method according to  claim 1 , wherein the image sensor comprises pixel array coupled to a filter array, each filter in the filter array being adapted to pass radiation of a part of the spectrum. 
     
     
         8 . The method according to  claim 7 , wherein the filter array comprising one or more color filters configured to pass radiation in a color band and/or one or more infra-red filters configured reflect visible radiation and to transmit infra-red radiation. 
     
     
         9 . The method according to  claim 8 , wherein the method further comprising the steps of:
 determining first image data from pixels responsive to radiation in one or more infra-red bands;   determining second image data from the pixels responsive to radiation in one or more color bands;   subjecting the first image data to a high frequency filter;   blending the filtered high frequency components of the first image data to the second image data, preferably the color components of the second image data.   
     
     
         10 . An aperture system for controlling the exposure of an image sensor to radiation, the system comprising:
 at least a first aperture for controlling exposure of the image sensor to radiation from a first part of the spectrum, and;   a least a second aperture for controlling exposure to radiation from a second part of the spectrum, the first and second apertures being different in size.   
     
     
         11 . The aperture system according to  claim 10 , wherein the aperture system comprises a transparent substrate, the substrate comprising an opening defining the first aperture, the substrate comprising a filter, preferably a thin film filter, defining a second aperture. 
     
     
         12 . The aperture system according to  claim 10 , wherein the aperture system comprises a transparent substrate, a first part of the substrate being covered by a first thin film filter defining the first aperture and a second part of the substrate being covered with a second thin film filter defining a second aperture. 
     
     
         13 . The aperture system according to  claim 12 , wherein the first filter is located in the center of the substrate and wherein the second filter is formed around the first filter, preferably around the first filter in a concentric ring. 
     
     
         14 . An image sensor comprising:
 a pixel array wherein each pixel comprises at least one photosensitive element;   a filter array coupled to the pixel array, the filter array comprises blocks of pixel filters, wherein each block comprises one or more color filters, each color filter adapted to pass radiation in color band and one or more infra-red pass filters adapted to reflect radiation in the visible spectrum and to pass radiation in an infra-red band.   
     
     
         15 . The imaging system, comprising:
 an image sensor;   a lens system for focusing radiation onto the image sensor; and,   an aperture system according to  claim 10 .   
     
     
         16 . The image system according to  claim 15 , wherein the imaging system is configured to simultaneously expose the image sensor with radiation from the first and second aperture of the aperture system.