neutral-density filter
中性密度滤光器，灰滤光器

• minute
• MIOS
• mipack fiuorescence
• mirage
• mired
• mired-shift value
• mirofilm camaera
• mirror
• mirror assembly
• mirror blank, mirror substrate
• mirror camera
• mirror cell and support system
• mirror coating
• mirror condenser
• mirror elements
• mirror extensometer
• mirror galvanometer
• mirror galvanometer oscillograph
• mirror housing
• mirror image
• mirror-image measurement
• mirror lens
• mirrorless
• mirrorlike beavior
• mirror lock lever