The first step of creating sound from an optical scan is loading in and displaying the data taken during scans. A piece of software loads that data in and generates the images shown here. The images are three dimensional, depth images where grey-scale values correspond to the height of the surface. The software allows the user to look at the data point by point (bottom left) in detail (right ) and all at once (top left).
A close up of the probe (the black cylinder at the right of the image) and a cylinder loaded on the machine (the brown cylinder on the left of the image). The probe shines a white light that is 1.8 mm wide (visible as the white line on the cylinder) and analyzes the intensity and color of reflected light to find the height of 180 points on a surface.
A view of a sample data set. A computer algorithm has created an image from the height data collected during the optical scan. The cylinder is displayed at the top left as if it has been opened up and flattened out. The height of the cylinder surface corresponds to the gray-scale value. Black is deepest and white is highest. The analysis software has also found the bottom of the groove and traced it in blue. Next the algorithm will look at the data along the blue lines, take the derivative between points to calculate the speed of the needle along that line and calculate the sound.
A View of the computer program used to read and display optical scans. The program shows an overview of a large data set which can be a small portion of a cylinder, or an entire cylinder and a detail of the cylinder surface. The software also displays a point by point profile of the data that was collected.
This method is meant to illustrate how data collection works for a cylinder. During acquisition, individual measurements of the height at 180 points along a line are taken in quick succession, at slightly different positions, as the cylinder rotates, and then stitched together in analysis software.
After an image has been produced a software algorithm finds the bottoms of the grooves and traces them in blue. The bottom of the groove is where playback stylus would have rested, and dictates the path the stylus would have taken around the cylinder. Therefor the data along the groove bottom is most important in producing audio.