heliograph
(1)日光仪，日光反射信号仪
(2)太阳照相机
(3)加光胶版

• SMD LED surface-mount device LED
• smear
• smear camera
• smeared image
• smectic mesophase
• smectic phase
• smelting
• smelting furnace
• Smith chart
• Smith-Lagrange invariant
• smog
• smoked glass
• smooth circuit
• smooth emission spectrum
• smooth finish
• smoothing tool
• smoothness
• smudge
• snap
• snap ga(u)ge
• snap-on red filter
• snap ring
• snapshot
• snap switch
• Snellen fraction