Description:

The command "plot scan" is a lower level command used internally by both the commands "plot phase" and "plot flatten". A previously plotted section may be scanned using this command to measure the plotted intensity on a channel by channel basis. To cause the results to be written to the monitor at the end of scanning be sure to set the verbose NVS parameter "plot" to one before starting.

Several NVS parameters affect the scanning process. In particular the head NVS parameter "scands" sets the scanning drum speed. A suitable value for this is 10 RPM. If necessary, a higher speed may be used to get the PLL to lock thereby sacrificing some signal to noise (ie. a lower drum speed is preferred). The sys NVS parameter "newd" is automatically enabled while scanning if not already enabled to provide the higher resolution drum velocity measurement required when spinning the drum very slowly (see section on the drumservo below). As a last resort if PLL lock is not obtained at slow drum speeds then the sys NVS parameter "scanntu" can be set to try it with different ntu values. If this parameter is zero then the scanning routines automatically pick an ntu value derived from the regular ntu value and scaled for the scanning drum speed. I expect that this will almost always work and hence there will be no need to adjust the sys NVS parameter "scanntu" but it is there just in case.

The best focus for the focus laser does not coincide with the best write laser focus and thus the head NVS parameter "scanlpos" is used to set the lens position while scanning. A suitable value is 200 assuming that the head was set up so that the write laser focus is close to an lpos of 0. While scanning the focus mode is internally set to 1 (lpos hold) and does not track the plate surface. This is okay since the focus laser depth of focus is much larger than for the write laser.

The offset parameter is in mil and the length parameter in 1/10th inches. The last optional parameter is the scan mode. Two modes exist with mode 2 the default. In mode 2 the channel information is preserved so this mode is needed when building scorr tables. Mode 1 is used when only the overal density is important such as when determining the best focus. The advantage of mode 1 is that it moves the carriage more slowly so useful data can be acquired from a much thinner strip. If scanning a previously plotted series which is done with the command "plot scan series" then mode 1 is implicitly used.

Applies To:

• Thermal

Syntax:

Notes:

See Also:

• Command: plot
• Command: plot flatten
• Command: plot phase
• NVS: head scands
• NVS: head scanlpos
• NVS: sys newd
• NVS: sys scanntu
• NVS: verbose plot