zero offsent optical square
零距直角头

• overall focal length
• overall integral metering
• overall length
• overall magnification
• overall size
• overall system gain
• overannnealing
• overarm
• overarm support
• overbalance
• overbunching
• overburden
• overcast
• overcharge
• overcoat
• overcoating
• overcompensation
• overcooling
• over correction
• overcurrent
• overdamping
• overdevelopment
• overdischarge
• overdrive gear
• overexcitation