Rowland, I have attached the PDF of the design. Look at VT1 and DD5 in the middle of the PDF. Nothing very exciting to see, the ATMega328 is PWM-ing the MOSFET and hence controlling the TEC. The TEC cannot be controlled during the sensor frame read (which takes about 2 seconds) so the TEC can be left on or off during the read. This will affect the sensor temperature a bit.
Gilles, great work on the indi drivers
I will have to try them out when ready.
Patrice, when you were getting horizontal stripes, did they look like in the attached image?