All of the records we processed were scanned with an Epson Expression 1640XL flatbed scanner (seen in the image at the left). We used a resolution of 1600 dpi (the maximum optical resolution of the scanner) and 8-bit grayscale. Although the bed of the scanner is large enough to scan an entire record (78 or 33 1/3), a single scan only yields usable information for a portion of the record. Because of this, we scanned each record 8 times, rotating the record after each scan so that every sector was positioned with the optimal alignment relative to the lamp in at least one image. The sectors overlap sufficiently to allow proper groove tracking across boundaries.
This image is taken from a section of a 78 where the grooves are roughly parallel to the scanner's light source. This orientation allows the maximum amount of light to be reflected from the grooves to the CCD.
This image, taken from a different portion of the same 78 scan, shows grooves that are nearly perpendicular to the light source. In this case the grooves are far less distinct, and are extremely difficult to extract from the image
This image is taken from a section of a 33 where the grooves are roughly parallel to the scanner's light source. Note the increase in groove density when compared with the 78.