What device converts light energy into electrons in an image intensifier?

The device that converts light energy into electrons in an image intensifier is the photocathode. This component is essential in the functioning of image intensifiers, as its primary role is to absorb the incoming light photons generated by the scintillator and convert them into photoelectrons. When light hits the photocathode, it prompts the release of electrons, which are then accelerated and focused by the subsequent components of the image intensifier, ultimately leading to an intensified image suitable for fluoroscopic examination.

In the context of the other options, while the electron gun and electrostatic lens play important roles in the operation of an image intensifier, they do not perform the task of converting light into electrons. The electron gun is responsible for generating and focusing the electron beam, and the electrostatic lens is involved in shaping the electron pathway. The photomultiplier, while it does amplify light signals, operates differently and is not typically found in image intensifiers, which specifically rely on the photocathode for the light-to-electron conversion.