Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1979-09-11
1981-07-07
Punter, William H.
Optics: measuring and testing
By polarized light examination
With light attenuation
356394, G01B 1100
Patent
active
042771757
ABSTRACT:
In order that a slight positional deviation of a plated through hole such as having no substantial effect on the function of wiring should not be optically detected as a defect in a printed wiring board, the plated through hole is recognized as a part of the wiring pattern by making light representative of the plated through hole nearly equal in intensity to reflected light from the wiring pattern. This is achieved by illuminating the printed wiring board with light from the back side or by placing a reflector on the back side of the printed wiring board.
REFERENCES:
Krochmann et al., "Automatic Vector Distance Comparator VDK Projektina", Feinwertechnik & Messtechnik, vol. 84, 10, 11-76, pp. 330-334.
Hara Yasuhiko
Karasaki Koichi
Hitachi , Ltd.
Punter William H.
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