4 ms·
Since when are CD reader optics interferometers? The linked video shows a CW homodyne LIDAR used for measuring vibration frequency and counting vibration amplit
by namibj 1y ago
Since when are CD reader optics interferometers?
The linked video shows a CW homodyne LIDAR used for measuring vibration frequency and counting vibration amplitude in fringes.
Last I looked CD readers used a 4-detector sensor's differential low-pass signals for closed-loop track-following so the rotation need not be optically centered.
I also see no reason why optical disc readouts would need homodyne let alone heterodyne readout.
- rowanG077 1y agoThe pits and valleys are spaced λ/4 apart. The reason there is such a stark difference in intensity is because this λ/4 spacing causes interference at pit->valley and valley->pit transition points. Of course this not a standard interferometer but rather a purpose build one. Wikipedia says: > Interferometry is a technique which uses the interference of superimposed waves to extract information. And a blu ray player directly uses interference of superimposed waves to extract information. It squarely fits in the homodyne category.