Haber document re-read, Wiki update, S/W update
1) Review all Haber documents new and old for method of obtaining radius. My comments on Haber's process for 78rpm lateral groove outlined below:
a) Illuminate and capture image such that groove bottom is sharply contrasted with sidewalls. Captured images show clear bright streaks and sharply contrasting sidewalls as dark streaks.
b) Program determines disk center and follows groove trajectory spiralling inwards in cylindrical coordinates (R, Φ)
c) Every 8 microns along groove, measure R of groove bottom by determing where the bright groove bottom streak transitions to the sidewalls. This leads to 2 R measurements every 8 microns (61.3 kHz @ 60mm radius), corresponding to the inner and outer light/dark transition of the groove bottom. Strong dependence on edge quality i.e. sharpness of contrast between groove bottom and sidewalls.
d) Take average of the 2 R measurements at every 8 microns
e) Find Ro, C, A, and Φo such that R’-R is minimized for the whole dataset where R’ = Ro + C*Φ’ + A*(sin(Φ’ + Φo))^2.
i. Ro fit eliminates DC bias
ii. C*Φ’ fit eliminates linear progressive bias. This results from constant steady pressure against the stylus as the groove pushes inward, thus there is no current-generating velocity of the stylus magnet in the inducting coil of the cartridge.
iii. A*(sin(Φ’ + Φo))^2 fit eliminates oscillating “wow” effect. This would be a low frequency modulation effect, with a frequency in the same magnitude as the disk revolution frequency. I missed this before - this acknowledges the existence of the sinusoid-ish rising/falling trends in the data we observed.
f) Once R’ is found to optimally fit R, R’-R is taken as the true undulation of the stylus magnet.
2) Working on Wiki update to fully document the software that was used for the extraction of the sine test tone in November. Will document each module separately.
3) Software update to version 2.0.0 moving along. Plan is to work in 3D, with more intelligent groove tracing algorithm. More details to follow.
a) Illuminate and capture image such that groove bottom is sharply contrasted with sidewalls. Captured images show clear bright streaks and sharply contrasting sidewalls as dark streaks.
b) Program determines disk center and follows groove trajectory spiralling inwards in cylindrical coordinates (R, Φ)
c) Every 8 microns along groove, measure R of groove bottom by determing where the bright groove bottom streak transitions to the sidewalls. This leads to 2 R measurements every 8 microns (61.3 kHz @ 60mm radius), corresponding to the inner and outer light/dark transition of the groove bottom. Strong dependence on edge quality i.e. sharpness of contrast between groove bottom and sidewalls.
d) Take average of the 2 R measurements at every 8 microns
e) Find Ro, C, A, and Φo such that R’-R is minimized for the whole dataset where R’ = Ro + C*Φ’ + A*(sin(Φ’ + Φo))^2.
i. Ro fit eliminates DC bias
ii. C*Φ’ fit eliminates linear progressive bias. This results from constant steady pressure against the stylus as the groove pushes inward, thus there is no current-generating velocity of the stylus magnet in the inducting coil of the cartridge.
iii. A*(sin(Φ’ + Φo))^2 fit eliminates oscillating “wow” effect. This would be a low frequency modulation effect, with a frequency in the same magnitude as the disk revolution frequency. I missed this before - this acknowledges the existence of the sinusoid-ish rising/falling trends in the data we observed.
f) Once R’ is found to optimally fit R, R’-R is taken as the true undulation of the stylus magnet.
2) Working on Wiki update to fully document the software that was used for the extraction of the sine test tone in November. Will document each module separately.
3) Software update to version 2.0.0 moving along. Plan is to work in 3D, with more intelligent groove tracing algorithm. More details to follow.
posted by Simon at 8:39 AM
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