CrossRoads:
How much current does the "galvo-motor" require to turn it?
The signal above is control signal for a driver board that needs the voltage above. So i suppose it is not that much. The driver board provides up to 1A.
You can make a virtual ground with your 15V power supply as the op-amp will need very little current.
Put a 100 ohm and 50 ohm resistor in series from the +15V to the 15V return.
Treat the center as Gnd, connecting it to the Arduino Gnd and to your galvo-motor Gnd,
Then you will have +10, Gnd, and -5V. Use that to power an op-amp with split supply, rail-to-rail output.
The arduino will have 0-5V output (use a lowpass RC filter on a PWM output). Use a summing amplifier circuit with gain of 3 and add in - voltage so then when 0V comes in -5V comes out, and when 5V comes on 10V goes out.
Since the Arduino doesn't have an analog output, I assume PWM will work with your motor & driver?
If you need DC you can filter the PWM (with an R-C filter into the op-amp).
If it is variable DC, you can use a [u]summing amplifier[/u] to sum the 0-5VDC signal with a negative bias and amplify it.
Note that a basic summing amplifier is an inverting amplifier so if you want to bias the output half-way between -5V and +10V (at +2.5V) you need a negative voltage into one of the summing inputs. You'll also need to invert the DC control voltage logic (in software). i.e. If you want the op-amp to go +10V, send zero into the summing amp. If you want to go to -5V, send +5 into the summing amp.
Also note that by using different resistor values, different inputs to your summing amplifier can have different gains. i.e You might want a bigger gain for the signal-input than for the bias-input.
But if you are using PWM, you can use an op-amp as a [u]comparator[/u] powered at slightly more than +10V and slightly more than -5V. Use a reference voltage of about 2.5V and the PWM will switch between positive (~ +10V) and negative (~ -5V) saturation.
Using your existing 15volt supply plus a negative ~7volt supply.
+15volt has to be stable, because it's also used as reference. Can be +12volt (change 15k resistor accordingly).
-7volt can be unregulated.
Leo..