Segmentation with Invisible Keying Signal

Chroma keying is the process of segmenting objects from images and video using color cues. A blue (or green) screen placed behind an object during recording is used in special effects and in virtual studios. A different background later replaces the blue color. A new method for automatic keying using invisible signal is presented. The advantages of the new approach over conventional chroma keying include: (i) unlimited color range for foreground objects. (ii) No foreground contamination by background color. (iii) Better performance in non-uniform illumination. (iv) Features for generating refraction and reflection of dynamic objects. The method can be used in real-time and no user assistance is required. A new camera design and a single chip sensor design for keying are also presented.


"Segmentation with Invisible Keying Signal,"
M. Ben-Ezra, In Proc. IEEE Computer Vision and Pattern Recognition (CVPR),
Hilton Head Island, South Carolina,
I:32-37, June 2000. [PDF]


Traditional chroma keying use a blue (or green) screen as the background keying signal. Clearly, this method is limited to objects with colors significantly different than the color of the background. Moreover, reflected light from the background tends to "contaminate" the foreground objects as sees in this example.

Our method utilizes light polarization, which is invisible to the human eye, as the keying signal. Polarized light from the background, and non-polarized light from the foreground is split by a polarizing beam splitter to form a pair of images. These images are processed by a computer to create a masking matte which is later used to make composite images as seen in the following examples.

Two different polarization images, a masking matte and composite images.

The same method cam be applied to transparent objects as seen in this example.


A video showing con-focal and simultaneous capturing of the input images, the resulting video matte, and a resulting composite video. [QT] [AVI]

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