Svenska Traforskningsinstitutet

Gerdt Fladda

Lennart Eriksson

A device for determining by means of light the average thickness of a layer, permeable to said light, arranged on a surface having properties different from those of the layer with respect to the light used, and also adapted to be used to provide a measure of the topography of a surface substantially opaque to the light used, includes an opaque shield that bears substantially perpendicularly with one edge against the layer when thickness is being determined or against the surface when surface topography is being measured. At least one light indicator shielded from direct incident light is arranged on the side of the shield opposite to the side on which the light source is located. The light indicator responds to the emitted luminous flux which it receives indirectly from the light source, which in a thickness determination is transferred to the indicator past the lower edge of the shield via the permeable layer, or in the measuring of surface topography passes through openings formed between the irregular surface being measured and the planar edge of the shield engaging that surface. The signal from the light indicator due to the transferred luminous flux is arranged, optionally after further evaluation, to indicate the layer thickness or surface topography.

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Gerdt Fladda