Mtec 2003 Preview
Advances in laser triangulation sensing
Micro-Epsilon claims to have overcome many of the disadvantages of PSD
(position sensitive device) based laser triangulation sensors with the
development of a new range of triangulation sensors based on digital
charged coupled device (CCD) technology. A highlight of the company's
stand this year, these smart CCD lasers can react quickly to changing
target surface conditions and are immune to the effects of stray and
secondary reflections.
The CCD element used by Micro-Epsilon is a digital pixelised array
detector with 1,024 discrete voltages representing the amount of light on
each pixel of the detector. The intensity distribution of the imaged spot
is 'viewed' with the help of a powerful DSP device and subsequently
processed to obtain the linear triangulation measurement. For a stable
measurement, as little as 1% diffuse reflectivity is necessary with a CCD
detector.
Smart CCD detectors also use closed loop control to adjust the power of
the transmitting laser according to the amount of reflected light
received from the target. An optimum light intensity for the sensing
element is achieved, regardless of target colour or surface texture.
Moreover, as the amount of reflected light required is so small, Class II
laser diodes can be used, thus avoiding all the safety issues associated
with Class III devices.