From Longman Dictionary of Contemporary Englisheyepieceeye‧piece /ˈaɪpiːs/ noun [countable] HPOthe glass piece that you look through in a microscope or telescope
Examples from the Corpus
eyepiece• The brighter light reflected on his glass eyepieces, gleamed on the moulded side muzzle of the respirator.• The heavy brown furniture, and Senor Menini: his eyepiece, the solder in his teeth, his dusty scales.• The slightest criticism generates an overwhelming impulse to impale myself on my microscope eyepieces.• Changing the eyepiece means changing the magnification.• Sofia concentrated on the eyepiece image and saw a table-shaped signal. ` See?• However, I have installed felt pads on the eyepieces of my microscope.• You will also find that the viewfinder eyepiece is positioned along the side of the camcorder body. 