Optoelectronic gauging, as an alternative to the traditional contact and air-to-electronic solutions, allows measurements to be performed without touching the part, providing high speed inspection coupled with high flexibility, so that several part types can be checked without any operator intervention.
To perform dimensional inspections, Marposs utilizes infra-red optoelectronic probes (CCD) based on the shadow casting principle.
The shadow cast operating principle consists in projecting the shadow of the edges of the part to be measured onto a linear array of photodiodes (CCD) by means of a precisely aligned light beam. The darkness-to-light and light-to-darkness transitions are located on the CCD sensor with a subpixel resolution and correlated with the dimensional value of the dark area.
The light coming from the emitter is generated by a LED that emits in the infrared range (lambda=760 nm).
The transmitted light is collected by the receiver, then filtered and projected onto the CCD sensor. Thus an inverted, monodimensional image of the object which is seen by the emitter, is now present on the CCD sensor.
The CCD is read electronically, and processes its signal by means of algorithms. This makes it possible to locate the darkness-to-light transitions on the CCD and to correlate them with the dimensional value of the dark areas that correspond to the profile of the measured part.
The diffracted beams generated by the presence of smoke, water vapour and suspended particles are filtered by a diaphragm located inside the receiver in the focal plane of the lenses.
An additional filter located in the receiver avoids the influence of external light sources.
In this way, only the aligned beams reach the CCD array.
This technology gives the optoelectronic probe the following characteristics: sturdiness, compactness, durability (> 40,000 hrs), low sensitivity to ambient temperature variation (0,2 µm/°C = .000 004”/°F).
For some applications, Marposs also uses laser probes, triangulation probes and diodes. Among these are the non-contact laser applications for tool setting.