I've checked the pins on diode test across the bottom two pins (at the sensor not the plug) where I expect the diode to be and don't get anything. I have a few of the same printer and I've got the same result for all.
Testing it powered up there's ~1.5v across where I think the diode is and 3.2V on the direction outputs. I've marked the 3V and 0V from this.
Wiring it up to my sketch I get nothing. I have tried to see the IR diode with my phone camera also.
I've proved the sketch with this photo interrupt .
There is nothing there to work with, just pictures of green and brown circuit boards with black blobs and wires. Consider reverse engineering the sensor and generating a schematic, by then it should become obvious. You can purchase them for less then a buck and get all the information and a lot less greaf. A lot more information is needed such as component part numbers, assembly part numbers and who made it?