Image processing systems and methods
An image capture system comprises a camera configured to capture an image of a whiteboard, or similar, viewed from an acute angle. A linear polarizer has a surface substantially perpendicular to a plane of the board and an axis of polarization substantially perpendicular to the plane of the board or within 30° of the perpendicular to the plane of the board. The camera is configured to capture the image of the board through the polarizer. A normal to the polarizer is directed in a different direction to a direction defined by an optic axis of the camera.
1. An image capture system comprising:
a camera configured to capture an image of a board viewed from an acute angle, the camera having an optic axis that extends in a different direction than a direction that is perpendicular to a plane of the board; and
a linear polariser extending from the board in the direction perpendicular to the plane of the board, wherein:
the linear polarizer further comprises an axis of polarisation substantially perpendicular to, or within 30° of, the plane of the board,
the linear polarizer has a polarizer surface disposed between the camera and the plane of the board, and
the camera is configured to capture the image of the board through the polarizer surface.
2. An image capture system as claimed in claim 1 , wherein the camera has a rectilinear lens.
3. An image capture system as claimed in claim 2 , wherein the optic axis is directed towards the board at an angle of less than 15° to a normal to a surface of the board.
4. An image capture system as claimed in claim 3 , wherein the optic axis of the camera is directed towards the board at an angle of between 12° and 0.5° to a normal to a surface of the board.
5. An image capture system as claimed in claim 1 , wherein the polariser surface is curved about an axis perpendicular to the plane of the board.
6. An image capture system as claimed in claim 5 , wherein the linear polariser is curved to define part of a curved surface of a cylinder having an axis normal to the plane of the board.
7. An image capture system as claimed in claim 5 , wherein the linear polariser is located at a greater distance from the camera than a location defined by an intersection of the optic axis of the camera with the plane of the board.
8. An image capture system as claimed in claim 1 , wherein the camera is located laterally adjacent an upper or lower edge of the board and is displaced vertically away from the plane of the board.
9. An image capture system as claimed in claim 8 wherein the optical axis of the camera is directed to miss or just intersect the upper or lower edge of the board.
10. An image capture system as claimed in claim 8 , wherein the camera is mounted approximately at a mid-point of the upper or lower edge.
11. An image capture system as claimed in claim 1 , wherein the acute angle is less than 30°.
12. An image capture system as claimed in claim 1 , configured to:
input, from the camera, camera data for a succession of image frames, wherein the image frames comprise successive images of the board from the camera;
process data from the image frames to remove parts of the image frames corresponding to parts of a user or user pen writing or drawing on the board and to generate processed data;
wherein the system is further configured to process the processed data by filtering to distinguish between a motion of parts of the user or user pen in the image frames and writing/drawing image information in the image frames which appears or changes during the writing or drawing but which is thereafter substantially unchanging; and
output writing/drawing data from the processed data, wherein the writing/drawing data defines captured writing or drawing on the board.
13. An image capture system as claimed in claim 12 , wherein the system is further configured to process the processed data by subdividing the image frames into blocks for blockwise processing, the blockwise processing comprising determining when image content of a block has changed by less than a threshold over a user filter time interval; and in response identifying that the block does not include the parts of the user or user pen.
14. An image capture system as claimed in claim 13 , wherein the determining comprises:
comparing corresponding blocks in frames at different times to determine a measure of a difference between pixel values of the corresponding blocks; comparing the measure against the threshold;
determining a time period for which the measure is less than the threshold; and
identifying that the block does not include user/pen parts when the measure is less than the threshold for greater than the user filter time interval.
15. A system, comprising:
a camera to be directed to capture an image from a board, the camera having an optic axis that extends in a different direction than a direction that is perpendicular to a plane of the board; and
signal processing apparatus, coupled to the camera and configured to:
input camera data for a succession of image frames, wherein the camera data is from a camera directed towards the board and the image frames comprise successive images of the board from the camera;
filter filtered data from the image frames to remove parts of the image frames corresponding to parts of a user or user pen writing or drawing on the board; and
output writing/drawing data from the filtered data, wherein the writing/drawing data defines captured writing or drawing on the board; and
a linear polariser extending from the board in the direction perpendicular to the plane of the board, wherein:
the linear polarizer further comprises an axis of polarisation substantially perpendicular to, or within 30° of, the plane of the board,
the linear polarizer has a polarizer surface disposed between the camera and the plane of the board, and
the camera is configured to capture the image of the board through the polarizer surface.
16. A system as claimed in claim 15 , wherein the linear polariser is curved about the direction perpendicular to the plane of the board.
17. An image capture system, the system comprising:
a camera with a rectilinear lens configured to capture an image of a board viewed from an acute angle;
wherein the camera is located laterally adjacent an upper or lower edge of the board and is displaced vertically away from a plane of the board,
wherein the camera has an optic axis that is directed towards the board at an angle of less than 15° to a normal to a surface of the board, and
a linear polariser extending from the board in a direction perpendicular to a plane of the board, wherein:
the linear polarizer further comprises an axis of polarisation substantially perpendicular to, or within 30° of, the plane of the board,
the linear polarizer has a polarizer surface disposed between the camera and the plane of the board, and
the camera is configured to capture the image of the board through the polarizer surface.
18. An image capture system as claimed in claim 17 , wherein the optic axis of the camera is directed towards the board at an angle of between 12° and 0.5° to a normal to the surface of the board.