Leow Wee Kheng CS4243 Computer Vision and Pattern Recognition

Camera Models and Imaging

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Camera Models and Imaging

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Through our eyes… 

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Through our eyes we see the world.

Camera Models and Imaging

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cornea focus light lens retina captures image transmit image

optic nerves iris pupil control amount of light entering the eye

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Camera Models and Imaging

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Through their eyes… 

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Camera is computer’s eye.

Camera Models and Imaging

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

Camera is structurally the same the eye. sensor | retina

lens lens | cornea CS4243

Camera Models and Imaging

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lens

aperture | pupil

lens | cornea CS4243

Camera Models and Imaging

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aperture plates | iris

aperture | pupil

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Camera Models and Imaging

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Imaging 

Images are 2D projections of real world scene.



Images capture two kinds of information:  Geometric:

positions, points, lines, curves, etc.  Photometric: intensity, colour. 

Complex 3D-2D relationships.



Camera models approximate relationships.

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Camera Models and Imaging

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Camera Models 

Pinhole camera model

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Orthographic projection

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Scaled orthographic projection

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Paraperspective projection

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Perspective projection

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Camera Models and Imaging

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Pinhole Camera Model image plane

2D image

pinhole

virtual image plane

3D object

focal length

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Camera Models and Imaging

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

Math representation world frame / camera frame

camera centre CS4243

image frame

image centre Camera Models and Imaging

projection line

optical axis 11



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By default, use right-handed coordinate system.

Camera Models and Imaging

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

3D point P = (X, Y, Z)T projects to 2D image point p = (x, y)T .



By symmetry,

i.e.,

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Simplest form of perspective projection.

Camera Models and Imaging

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Orthographic Projection

 3D

scene is at infinite distance from camera.  All projection lines are parallel to optical axis.  So,

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Camera Models and Imaging

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Scaled Orthographic Projection

depth