ENDOSCOPE FRONT END ASSEMBLY, ENDOSCOPE INSERTION PORTION, AND ENDOSCOPE

Provided are an endoscope front end assembly, an endoscope insertion portion, and an endoscope. The endoscope front end assembly comprises a fitting member (100), a lens holder (200), and a transmission mechanism (300). The fitting member (100) is provided with an instrument tube mounting cavity (110) extending in an axial direction thereof. The lens holder (200) is rotatably arranged at the distal end of the fitting member (100) by means of the transmission mechanism (300). The instrument tube mounting cavity (110) has a hidden state and an exposed state. The instrument tube mounting cavity (110) can be switched between the hidden state and the exposed state along with the rotation of the lens holder (200). The lens holder (200) can shield the instrument tube mounting cavity (110) or expose the instrument tube mounting cavity (110) under the action of the transmission mechanism (300). In the case that it is ensured that the instrument tube mounting cavity (110) has a suitable opening size, the mode is benefi