manufacturer of the scan-fail interlock to determine whether or not the
scan-fail interlock itself has a differential position input. If the scan-
fail monitor does not have a differential position input, you should
NOT connect the “Signal ground” or “Position ground” from the
scanner amplifier to the scan-fail monitor. Doing so would, again,
destroy the single-point grounding scheme. The scan-fail monitor
already has a ground connection to the “Central Grounding Point”
established on the Power Connections diagram. You should only
connect the scan-fail monitor to the scanner amplifier’s ground
connection if the scan-fail monitor itself has differential inputs.
Pangolin’s PASS safety system does have a differential position input,
but most others do not.
The scan-fail monitor would also be connected to a shutter or to the
laser diode drivers, but the method of connection depends on the exact
scan-fail monitor being used. Consult the manufacturer of the scan-
fail monitor for details.
The color signals are connected in exactly the same way as the X and
Y signals were connected, using differential signaling. ILDA DB-25
pin 5 is connected to the “positive modulation input” on the red laser
diode driver, while pin 18 is connected to the “negative modulation
input”. ILDA DB-25 pin 6 is connected to the “positive modulation
input” on the green laser diode driver, while pin 19 is connected to the
“negative modulation input”. ILDA DB-25 pin 7 is connected to the
“positive modulation input” on the blue laser diode driver, while pin
20 is connected to the “negative modulation input”.
The discussion about color signals above, as well as the diagram
makes the assumption that the laser diode driver has differential inputs
to begin with. As two examples, laser diode drivers made by
Laserwave and by Viasho do have differential inputs, but, as two
other examples, laser diode drivers made by CNI and Melles Griot do
not. Also, it is possible that the laser projector would have an ion laser
and PCAOM used for color modulation. In this case, the same
connection scheme and discussion applies. PCAOM drivers made by
NEOS do have differential inputs, but PCAOM drivers made by AA
do not. (In general scanner amplifiers to have a differential input,
however some very low cost scanner amplifiers may not.)
Since the ISP standard absolutely requires all motion and color signals
to be implemented as differential pairs within the projector, this
means that if you have scanner amplifiers or laser diode drivers that
do not have differential inputs, you will need to implement the
differential receiver as a separate circuit.
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