mechanical optical switches
光开关(机械式)

• pentaprism
• penta reflector
• pentavalent
• pentode
• Pentovar lens
• pentoxide
• penumbra
• penumbra cone
• penumbra region
• perambulator
• percent
• percentage
• percentage error
• percentage of articulation
• percentage of modulation depth
• per cent weight
• perception
• perception of brightness
• percieved modulation
• percolation
• percussion
• perfect blackbody
• perfect comparator
• perfect crystal
• perfect detector