a collimator is included in a microchannel plate image intensifier . collimators can be useful in improving resolution of mcpis by eliminating the scattered electron problem and by limiting the transverse energy of electrons reaching the screen . due to its optical absorption , a collimator will also increase the extinction ratio of an intensifier by approximately an order of magnitude . additionally , the smooth surface of the collimator will permit a higher focusing field to be employed in the mcp - to - collimator region than is currently permitted in the mcp - to - screen region by the relatively rough and fragile aluminum layer covering the screen . coating the mcp and collimator surfaces with aluminum oxide appears to permit additional significant increases in the field strength , resulting in better resolution .