Imaging device with an improved autofocusing performance
The invention describes an imaging device ( 1 ) comprising an image sensor ( 2 ), an imaging lens ( 3 ), an infrared light source ( 5 ) to illuminate a scene (SC), and an infrared autofocus system ( 6 ) for providing an autofocus function, wherein the image sensor ( 2 ) comprises an array ( 21 ) of sensor pixels each arranged as dual pixel ( 22 ) comprising two separate pixel sensors ( 22 a , 22 b ) per dual pixel ( 22 ) to record the image data (D 1 ) as a sum signal from both pixel sensors ( 22 a , 22 b ) and providing infrared data (D 2 ) as individual signals from each of the two pixel sensors ( 22 a , 22 b ) for phase contrast (PC) autofocusing, wherein an infrared filter ( 7 ) arranged between an aperture ( 4 ) of the imaging device ( 1 ) and an imaging sensor ( 2 ) and is adapted to locally transmit only a portion of the infrared light (IR) to the imaging sensor ( 2 ) by comprising at least one first area ( 71 ) arranged as infrared blocking area and at least one second area ( 72 ) arranged as infrared bandpass area. The invention further relates to a method ( 100 ) to automatically focusing this device ( 1 ).
1. An imaging device, comprising:
a light source configured to illuminate a scene with infrared light;
an imaging lens configured to form an image of the scene using infrared light reflected from the scene and visible light that is reflected from the scene or emitted by the scene;
a filter configured to partially attenuate the infrared light reflected from the scene, the filter including a first area that is substantially transparent to infrared light and substantially transparent to visible light, the filter including a second area that is substantially opaque to infrared light and substantially transparent to visible light, the imaging lens defining a central axis that extends through the second area of the filter, the first area being annular and extending around the central axis;
a detector positioned to detect the image, the detector including a plurality of detector pixels, the plurality of detector pixels including at least two pixels that are summed together to produce data representing a single area within the image; and
an autofocus mechanism configured to adjust a spacing between the imaging lens and the detector such that the image is formed in a plane of the detector, the autofocus mechanism configured to adjust the spacing in response to an autofocus signal generated by the detector.
2. The imaging device of claim 1 , wherein the detector includes detector pixels that are grouped into pairs, each pair of detector pixels configured to produce signals that are summed together to produce data representing a single area within the image.
3. The imaging device of claim 1 , wherein the second area is centered with respect to the central axis.
4. The imaging device of claim 1 , wherein the autofocus signal is generated via phase contrast at the detector.
5. The imaging device of claim 1 , wherein the filter is positioned between the imaging lens and the detector.
6. The imaging device of claim 1 , wherein the filter is positioned between the imaging lens and the scene.
7. The imaging device of claim 1 , wherein the detector pixels are sensitive to both the infrared light and the visible light.
8. A method for operating an image device, the method comprising:
illuminating a scene with infrared light;
forming an image of the scene using infrared light reflected from the scene and visible light that is reflected from the scene or emitted by the scene;
partially attenuating the infrared light reflected from the scene with a filter, the filter including a first area that is substantially transparent to infrared light and substantially transparent to visible light, the filter including a second area that is substantially opaque to infrared light and substantially transparent to visible light, the image being formed with an imaging lens that defines a central axis that extends through the second area of the filter, the first area being annular and extending around the central axis;
detecting the image with a detector, the detector including a plurality of detector pixels, the plurality of detector pixels including at least two pixels that are summed together to produce data representing a single pixel of the image; and
adjusting, with an autofocus mechanism, a spacing between the imaging lens and the detector such that the image is formed in a plane of the detector, the autofocus mechanism adjusting the spacing in response to an autofocus signal generated by the detector, the autofocus signal being generated using data from each pixel individually in each pair of detector pixels.
9. The method of claim 8 , wherein the detector includes detector pixels that are grouped into pairs, each pair of detector pixels configured to produce signals that are summed together to produce data representing a single pixel of the image.
10. The method of claim 8 , wherein the second area is centered with respect to the central axis.
11. The method of claim 8 , wherein the autofocus signal is generated via phase contrast at the detector.
12. An imaging device, comprising:
a light source configured to illuminate a scene with infrared light;
an imaging lens configured to form an image of the scene using infrared light reflected from the scene and visible light that is reflected from the scene or emitted by the scene;
a filter configured to partially attenuate the infrared light reflected from the scene, the filter including a first area that is substantially transparent to infrared light and substantially transparent to visible light, the first area includes a plurality of subareas that do not adjoin one another, the filter further including a second area that is substantially opaque to infrared light and substantially transparent to visible light, each subarea being surrounded by the second area;
a detector positioned to detect the image, the detector including detector pixels that are grouped into pairs, each pair of detector pixels configured to produce signals that are summed together to produce data representing a single pixel of the image; and
an autofocus mechanism configured to adjust a spacing between the imaging lens and the detector such that the image is formed in a plane of the detector, the autofocus mechanism configured to adjust the spacing in response to an autofocus signal generated via phase contrast at the detector, the autofocus signal being generated using data from each pixel individually in each pair of detector pixels.
13. The imaging device of claim 12 , wherein the imaging lens defines a central axis that extends through the second area of the filter, the subareas being equidistant from the central axis.