Detecting a location of the needle inside a cavity having multiple IR emitters , using IR Detector at the tip of the needle
An idea is to use short pulses of increasing length for the different emitters, then using an MCU, calculate the height ratio between the peak levels.
This method should be quite tolerant to the distance of the emitters and mostly conjugates to the position of the needle between the different LEDs.
It should also be fairly easy to accomplish with a bit of analog circuitry and coding.
Synced LED Pulse:

Signal on the receiver &amp; detection of the ratio (sorry not very well aligned graph):

From the distances %, you can evaluate how far you are from each LED, it could even, theoretically, do 3D positioning.
Another method could also be TOF (Time of Flight)