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Restoration of Delaminated and Cracked Recordings Using Synthetic - - PowerPoint PPT Presentation
Restoration of Delaminated and Cracked Recordings Using Synthetic - - PowerPoint PPT Presentation
Restoration of Delaminated and Cracked Recordings Using Synthetic Depth of Field Optical Scanning of Disc Recordings IRENE 2D Setup Delamination on Lacquer Discs Image source: [1] A Closer Look Ways to Handle Cracks Crack detection (S.
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IRENE 2D Setup
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Delamination on Lacquer Discs
Image source: [1]
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A Closer Look
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Ways to Handle Cracks
- Crack detection (S. Fischer [2])
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Detect crack with displacement sensor
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Rescan the blurred area
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Works well for small number of radial cracks
- Synthetic depth of field
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Acquire a stack of subscans with different height offsets
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Merge the subscans
Image source: [3]
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Questions to be Answered
- Spacing of the scans?
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Determine depth of field of the current system
- How can sharp regions be detected?
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Focus measures
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Which is the right one for this application?
- How can the images be efficiently fused?
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Size of one image 300 MB - 800 MB
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Depth of Field How can the relevant depth of field for the audio extraction be determined? Microscopy theory: Problem: that does not tell us anything about how the depth of field affects the audio DoF= λ0n NA
2+
n M NA e≈38μ m
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Depth of Field
Experimental approach:
- Scan a silent portion of
the groove
- Extracted audio contains
- nly noise
- Change focus plane
- Signal RMS can be used
as noise measure
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Depth of Field Just notable difference ~ 1 dB [4] => 40 μm spacing
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Depth of Field
Z-offset 0 um Z-offset +40 um
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Acquisition System
Before: Tracking New: Focus Stacking
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Image stack
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Outlook
- Currently working on the image fusion algorithm
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Sources
[1] Northeast Document Conservation Center. IRENE Seeing Sound Blog. A Hefty Challenge for IRENE: Working with Delaminating Lacquer Discs, August 2014. https://www.nedcc.org/audio-preservation/irene-blog/ [03/14/2015]. [2] S. Fischer. Restoring Cracked Early Recordings. Master’s thesis, Zurich University of Applied Sciences, September 2013. [3] M. M. Karim. Focus stacking Tachinid fly. March 2009. http://commons.wikimedia.org/wiki/File:Focus_stacking_Tachinid_fly.jpg [05/31/2015] [4] Wikipedia. Just-noticeable difference. http://en.wikipedia.org/wiki/Just-noticeable_difference [06/04/2015].
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Perpendicular Lighting
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