front operating aperture
前工作孔径

• background wave
• backing
• backing-off
• backing paper
• backing sheet
• backlash
• Backlight and Components
• back lighting
• back-off
• back-out
• back over
• back-pack camera
• backplan
• back projection
• back-reflection Laue photograph
• back-reflection photograph
• back resistance
• back-roll
• back-run
• backscatter
• backscatter device
• backscattered light
• backscatterer
• back-scattering
• backscattering coefficient