symmetrical doublet lens
对称式双组镜头

• marking press
• mark photo sensors
• mark scraper
• marresisttance
• martensite
• Martens photometer
• martens wedge
• martin's diameter
• marx effect
• Marx generator
• maser 1
• maser action
• maser interferometer
• maser transition
• mask
• masked rom
• masking aperture
• masking blade
• masking-diffusion
• masking technique
• mask making equipment
• mask spectrometer
• Masksutov corrector
• Masksutov objective
• Masksutov telescope