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US 9,001,261 B2Granted
Optical focus of an image acquisition system
AssigneesAirbus Defence and Space GmbH, Centre National D'éTudes Spatiales C N E S
InventorPierre-Luc Georgy
Life of this patent
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Abstract
A method for characterizing an optical focusing defect of an image capture instrument is based on contrast values. Said contrast values are calculated for two images of a same scene portion, captured in respective overlapping length segments of two image sensors. To this end, the sensors are mounted in an image capture instrument so that the overlapping length segments between the sensors are situated at different heights along a focusing direction perpendicular to said sensors.
Claims25
A method for characterizing an optical focusing defect of an image capture instrument, wherein the instrument comprises:
- an image formation optical system configured for forming an image of a scene in at least one focal plane;
- at least two image sensors, each of which comprises a set of pixel detection elements arranged at intersections of at least one line and columns of a sensor matrix, both sensors being placed parallel to said at least one focal plane and oriented so that directions of respective lines of the sensors are identical or optically conjugated by a focal plane duplication system, and wherein the at least two image sensors are offset relative to one another parallel to the directions of the lines with a partial overlap of said sensors along the directions of the lines, so that each sensor has a length segment overlapping the other sensor and a complementary segment that does not overlap the other sensor;
- a control unit configured for controlling an image capture operation coordinated between the at least two image sensors;
- and
- an optical focusing system suitable for shifting said at least one focal plane of the image formation optical system with respect to the sensors in a direction perpendicular to each sensor;
- wherein the method comprises the following steps:
- capturing two images of a same portion of the scene respectively with both of the at least two image sensors in the respective overlapping length segments of said sensors;
- calculating two values of a contrast separately for the two images of the same scene portion;
- and
- deriving a direction of the optical focusing defect along the direction perpendicular to each sensor, based on a comparison of the contrast values calculated respectively for the two images of the scene portion;
- wherein:
- the at least two image sensors are mounted within the instrument with respective average heights that are different in the respective overlapping length segments, said heights being measured along the direction perpendicular to each sensor with respect to a shared reference plane or reference planes respectively associated with each sensor and conjugated with one another by the focal plane duplication system;
- and
- the two images are captured for one and the same adjustment of the focusing system, so that said at least one focal plane of the image formation optical system is situated for said images at different respective defocusing distances of the at least two image sensors.
11 more elements
An image capture instrument comprising:
- an image formation optical system configured for forming an image of a scene in at least one focal plane;
- at least two image sensors, each of which comprises a set of pixel detection elements pixels arranged at intersections of at least one line and columns of a sensor matrix, both sensors being placed parallel to said at least one focal plane and oriented so that respective line directions of said sensors are identical or optically conjugated by a focal plane duplication system, wherein the at least two image sensors are offset to one another parallel to the directions of the lines with a partial overlap of said sensors along the directions of the lines, so that each sensor has a length segment overlapping the other sensor and a complementary segment that does not overlap the other sensor;
- a control unit configured for controlling an image capture operation coordinated between the at least two image sensors;
- an optical focusing system configured for shifting said at least one focal plane of the image formation optics with respect to the sensors along a direction perpendicular to each sensor;
- and
- an optical focus controller configured for controlling execution of the following steps:
- in cooperation with the control unit, capturing two images of the same portion of a scene respectively with both of the at least two image sensors in the different respective overlapping length segments of said sensors;
- calculating two values of a contrast separately for the two images of the same scene portion;
- and
- deriving a direction of the optical focusing defect along the direction perpendicular to each sensor, based on a comparison of the contrast values obtained respectively for the two images of the scene portion;
- wherein:
- the at least two image sensors are mounted within the instrument with respective average heights that are different in the respective overlapping length segments, said heights being measured along the direction perpendicular to each sensor with respect to a shared reference plane or reference planes respectively associated with each sensor and conjugated with one another by the focal plane duplication system;
- and
- the focus controller is configured for controlling the capture of the two images for a same adjustment of the focusing system, so that said at least one focal plane of the image formation optical system is situated for said images at respective defocusing distances of the at least two image sensors.
11 more elements
A method of assembling an image capture instrument, comprising the following steps:
- providing an image formation optical system configured for forming an image of a scene in at least one focal plane;
- placing at least two image sensors parallel to said at least one focal plane (PF), each sensor comprising a set of pixel detection elements arranged at intersections of at least one line and columns of a matrix of said sensor, wherein both sensors are oriented so that respective line directions of said sensors are identical or optically conjugated by a focal plane duplication system, and wherein the at least two image sensors are offset to one another parallel to the directions of the lines with a partial overlap of said sensors along the directions of the lines, so that each sensor has a length segment overlapping the other sensor and a complementary segment that does not overlap the other sensor;
- adjusting the respective average heights of the at least two image sensors within the instrument so that said average heights are different between the at least two image sensors in the respective length segments that overlap, wherein said heights are measured along the direction perpendicular to each sensor with respect to a shared reference plane (PRef) or reference planes respectively associated with each sensor and conjugated with one another by the focal plane duplication system;
- supplying a control unit configured for controlling an image capture operation coordinated between the at least two image sensors;
- supplying an optical focusing system configured for shifting said at least one focal plane of the image formation optics with respect to the sensors in a direction perpendicular to each sensor;
- and
- supplying an optical focus controller;
- wherein the optical focus controller is configured for characterizing an optical focusing defect direction of the image capture instrument.
5 more elements
A method for characterizing an optical focusing defect of one image capture instrument among two image capture instruments, wherein each instrument comprises, separately from the other instrument:
- an image formation optical system configured for forming an image of a scene in a focal plane;
- an image sensor placed parallel to a focal plane and comprising an assembly of pixel detection elements arranged at the intersections of at least one line and columns of a sensor matrix;
- and
- an optical focusing system configured for moving the focal plane of the image formation optical system with respect to the sensor along a direction perpendicular to the sensor;
- wherein the two instruments are arranged in parallel so that the entrance optical fields respectively conjugated with the two sensors by the respective image formation optical systems, exhibit a partial overlap in the scene, and wherein the two instruments are oriented around respective optical axes so that lines of pixel detection elements of the two sensors are parallel to a shared direction in the scene, respective length segments of the two sensors, each of which is conjugated with the overlap of the entrance optical fields, being denoted as overlapping length segments of the sensors;
- wherein a control unit is configured for controlling an image capture operation coordinated between the two instruments;
- and
- wherein the method comprises the following steps:
- capturing two images of a same portion of a scene respectively with both of two instruments in the respective overlapping length segments of the sensors;
- calculating two values of a contrast separately for the two images of the same scene portion;
- and
- deriving a direction of the focusing defect along the direction perpendicular to each sensor based on a comparison of the contrast values calculated respectively for the two images of the scene portion;
- wherein:
- the two images are captured for respective adjustments that are different for the two focusing systems so that the respective focal planes of the two image formation optical systems are situated, for said images, at different respective defocusing distances of the two sensors.
11 more elements
Dependencies are inferred from the claim text.