Surface roughness gauge and method

A surface roughness gauge (10) for measuring the surface (12) of an article (14), comprising:

• first means (30) for directing a light beam directly upon the surface (12) and including a light emitting diode (36);
• second means (34) for providing a first signal proportional to the specular light reflected from the surface (12) and including a first photo diode (38) defining a common plane (40) with the light emitting diode (36);
• third means (58) for providing a second signal proportional to the diffused light reflected from the surface (12) and including a second photo diode (60) disposed on the common plane (40);
• fourth means (61) providing a third signal proportional to the diffused light reflected from the surface (12) and including a third photo diode (63) located to the side of the common plane (40);
• a sensor head (28) for mounting the diodes (36,38,60,63) is fixed positions thereon;
• and
• fifth means (24,66) for receiving and processing said first, second and third signals and displaying a reading (26) directly corresponding to surface roughness in a linear unit of measurement.

A method of measuring the surface roughness of an article (14) comprising:

• directing beam of light from a first device (36) upon the surface (12) of the article (14);
• providing a first voltage signal at a second device (38) proportional to the specular light reflected from the surface (12);
• providing a second voltage signal at a third device (60) proportional to the diffused light reflected from the surface (12) in a common plane (40) with the first and second devices (36,38);
• providing a third voltage signal at a fourth device (63) proportional to the diffused light reflected from the surface (12) at one side of the common plane (40);
• and
• processing the first, second and third voltage signals and displaying a reading (26) directly corresponding to surface roughness in a linear unit of measurement.