The analog signal after correction is then converted into 8-bit digital signals that comply with the individual levels of pixel voltage by the A/D converter.
5.3.7.5 Shading Correction (outline)
An original of even density does not necessarily mean uniform CCD output because of the following factors: 1. variation in the sensitivity of each pixel of the CCD 2. uneven intensity across the rod lens array 3. difference in intensity of light between the center and ends of the scanning lamp 4. deterioration of the scanning lamp The machine performs shading correction to correct any discrepancy in the output of the CCD. It performs shading correction at power-on and or for each job.
5.3.7.6 Shading Correction
The machine executes shading correction for each scan of the original. It measures the density of the standard white plate, and compares the measurement against the target value stored in the shading correction circuit; the machine then sets up the difference as the shading correction value, and uses it to correct any variation among CCD pixel when scanning the originals, thus evening out the image density levels.
