photoelectric auto-collimator
光电自准直仪

• narrow-band ir laser reflector
• narrow-band optical bandpass filter
• narrow-band quantus counter
• narrow beam
• narrow beam injection laser
• narrow central pencil
• narrow guide
• narrow illumination cone
• narrow limitation
• narrow line laser
• narrow planar stripe laser
• narrow-pulse
• nasopharyngoscope
• National Bureau of Standards
• National Science Foundation
• national standard
• natural
• natural abrasive
• natural aging
• natural colour film
• natural frequency
• natural light
• natural line width
• natural logarithm
• natural oscillation