“Gum Ball” Coded Aperture Example (*)

Original		MURA mask		inverse mask
	coded image		rescaled image
10% noise	5% noise	2% noise	1% noise	0.5% noise
0.2% noise	0.1% noise	0.05% noise	0.02% noise	0.01% noise

(*) Image of gum ball machine from Paul Carlisle's Coded Aperture Imaging page.

• The images are all 211 x 211 pixels.
• The “coded image” looks uniform in color because it has only about 1% contrast!
• The “rescaled image” expands the small contrast range to make the texture more visible.
• Gaussian noise added to the coded aperture image measurements before reconstruction.
• Decoded result is rescaled so each of the three color channels falls in 0 to 255 range.
• Conclusion: Accurate reconstruction requires unrealistically high SNR
• Conclusion: For visible light applications, must use low fill factor mask (i.e. not 50%)