Method, lens assembly and camera for reducing stray light

Patent metadata

Field	Value
Publication number	US-9438814-B2
Application number	US-201414260860-A
Country	US
Kind code	B2
Filing date	Apr 24, 2014
Priority date	Apr 25, 2013
Publication date	Sep 6, 2016
Grant date	Sep 6, 2016

Abstract

The present invention relates to a method ( 300 ) for reducing stray light in an output image of a scene, said method comprising; providing ( 301 ) a camera ( 100 ) comprising a lens assembly ( 102, 202 ), providing ( 302 ) an aperture unit ( 103, 203 ) having an aperture gate ( 204 a , 204 b ) in an aperture plane being orthogonal to an optical axis (OA) of said lens assembly ( 102, 202 ), said aperture gate ( 204 a , 204 b ) being adjustable in said aperture plane, acquiring ( 303 ), by means of said camera ( 100 ), a plurality of images of said scene, wherein each image of said plurality of images is acquired using an unique aperture gate setting, wherein each of said unique aperture gate settings correspond to a unique combination of a position and a shape of said aperture gate ( 204 a , 204 b ) in said aperture plane, analyzing ( 305 ) said plurality of images for generating data pertaining to a difference in stray light content with respect to said plurality of images, and producing ( 306 ) said output image based on said data pertaining to said difference in stray light content.

First claim

The invention claimed is:

1. A method for identifying stray light in a plurality of images of a scene using a camera comprising an image sensor, and a lens assembly comprising a lens for focusing light onto the image sensor, an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a position, a shape and/or a size being adjustable in said aperture plane by using said aperture unit, said method comprising:
acquiring, by using said camera, the plurality of images of said scene, wherein each image of said plurality of images is acquired using an unique aperture gate setting within said plurality of images, wherein said unique aperture gate setting corresponds to a unique combination of the position, the shape and/or the size of said aperture gate in said aperture plane,
dividing each of said plurality of images into corresponding pixel groups,
calculating a mean pixel level or a contrast value pixels comprised in said corresponding pixel groups of each of said plurality of images, and
comparing calculated mean pixel levels or contrast values for identifying stray light in said plurality of images.

2. A method for producing an producing an output image of a scene based on an identification of stray light in a plurality of images of the scene
using a camera comprising an image sensor, and a lens assembly comprising a lens for focusing light onto the image sensor, an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a position, a shape and/or a size being adjustable in said aperture plane by using said aperture unit, said method comprising:
acquiring, by using said camera, a plurality of images of said scene, wherein each image of said plurality of images is acquired using an unique aperture gate setting within said plurality of images, wherein said unique aperture gate setting corresponds to a unique combination of the position, the shape and/or the size of said aperture gate in said aperture plane,
dividing each of said plurality of images into corresponding pixel groups,
calculating a mean pixel level or a contrast value for pixels comprised in said corresponding pixel groups of each of said plurality of images, and
comparing calculated mean pixel levels or contrast values for identifying stray light in said plurality of images,
generating, as a result of said comparing, data pertaining to a difference in stray light content within corresponding pixel groups, and
producing said output image based on said data pertaining to the difference in the stray light content.

3. The method according to claim 2 , wherein said producing further comprises:
selecting one of a plurality of unique aperture gate settings based on said data pertaining to the difference in the stray light content,
using said selected unique aperture gate setting to acquire an additional image, and
using said additional image as said output image.

4. The method according to claim 2 , wherein said producing further comprises:
for each corresponding pixel group, selecting among the plurality of images, one of a plurality of unique aperture gate settings, by determining, based on said data pertaining to the difference in the stray light content, for which of said acquired images said mean pixel level is lowest or for which of said acquired images said contrast value is highest,
creating a merged aperture gate setting based on said selected aperture gate setting, by combining at least two of said selected aperture gate setting used in said acquiring,
using said merged aperture gate setting to acquire an additional image, and
using said additional image as said output image.

5. The method according to claim 2 , wherein said producing further comprises:
selecting one of said plurality of images based on said data pertaining to the difference in the stray light content, and
using said selected image as said output image.

6. A camera comprising:
an image sensor, and
a lens assembly comprising:
a lens for focusing light onto the image sensor,
an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a position, a shape and/or a size being adjustable in said aperture plane by using said aperture unit, and
a processing unit arranged to:
acquire, by using camera, a plurality of images scene, wherein, each image of said plurality of images is acquired using an unique aperture gate setting within said plurality of images, wherein said unique aperture gate setting corresponds to a unique combination of the position, the shape and/or the size of said aperture gate in said aperture plane,
divide each of said ality of images into corresponding pixelgroups,
calculate a mean pixe evel or a contrast value for pixels comprised in said corresponding pixel groups of each of said plurality of images, and
compare calculated mean pixel levels or contrast values for identifying stray light in said plurality of images.

7. A camera comprising:
an image sensor, and
a lens assembly comprising:
a lens for focusing light onto the image sensor,
an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a positi , a shape and/or a size being adjustable in said aperture plane by using said aperture unit, and
a processing unit arranged to:
acquire, by using said camera, a plurality of images of a scene, wherein each image of said plurality of images is acquired using an unique aperture gate setting within said plurality of images, wherein said unique aperture gate setting corresponds to a unique combination of the position, the shape and/or the size of said aperture gate in said aperture plane,
divide each of said plurality of images into corresponding pixel groups,
calculate a mean pixel level or a contrast value for pixels comprised in said corresponding pixel groups of each of said plurality of images, and
compare calculated mean pixel levels or contrast values for identifying stray light in said plurality of images,
generate, as a result of said comparing, data pertaining to a difference in stray light content within corresponding pixel groups, and
produce an output image based on said data pertaining to the difference in the stray light content.

8. A system comprising:
a camera comprising:
an image sensor, and
a lens assembly comprising:
a lens for focusing light onto the image sensor,
an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a position, a shape andior a size being adjustable in said aperture plane by using said aperture unit, and
a processing unit arranged to:
acquire, by using said camera a plurality of images of a scene, wherein each image of said plurality of images is acquired using an unique aperture gate setting within said plurality of images wherein said unique aperture gate setting corresponds to a unique combination of the position, the shape and/or the size of said aperture gate in said aperture plane,
divide each of said plurality of images into corresponding pixel groups,
calculate a mean pixel level or a contrast value for pixels comprised in said corresponding pixel groups of each of said plurality of images, and
compare calculated mean pixel levels contrast values for identifying stray light in said plurality of images.

9. A system comprising:
a camera comprising:
an image sensor, and
a lens assembly comprising:
a lens for focusing light onto the image sensor,
an aperture unit having an aperture gate arranged in an aperture plane, said aperture gate having a position, a shape andior a size being adjustable in said aperture plane by using said aperture unit, and

a processing unit arranged

Assignees

• Axis Ab

Inventors

• Hjelmstrom Jonas
• Johannesson Anders

Classifications

• H04N23/75 Primary

  by influencing optical camera components · CPC title

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• H04N23/55

  Optical parts specially adapted for electronic image sensors; Mounting thereof · CPC title

• H04N23/741 Primary

  by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors · CPC title

• H04N23/71

  Circuitry for evaluating the brightness variation · CPC title