Temperature Stability

Implementing 3D sensors directly into the manufacturing process provides the maximum value to the user.  This however exposes the sensors to an uncontrolled environment, where ambient temperature can vary dramatically.  Even more severe are applications where sensors monitor the level of molten metal, or are mounted on vehicles profiling roads in the outdoors.  For many types of sensors, not taking the changing temperature of the environment into account can cause drift.  For 3D sensors which are optical in nature, the amount of thermal drift increases with increasing stand off, and many 3D sensors have large stand offs.

For 3D sensors, thermal drift is caused by several factors. The projected laser spot or line position can shift with temperature due to temperatures effecting mechanical mounting components creating an apparent measurement error.  In some situations, the sensor's internal components may change position due to thermal expansion and twisting of their mounting elements, or, cause a shift in laser frequency.

LMI takes several steps to insure thermal stability of our 3D sensors.

First, we have designed a proprietary laser and optics package which provides unrivalled pointing stability of the laser beam.

Second, we mount all optical components on a solid mounting frame or spine, which is CNC machined from a solid block, keeping components in their designed locations.

Third, where temperature stability is critical, temperature compensation is implemented, with temperature sensors mounted in each sensor. As part of our manufacturing process, sensors are placed in an environmental chamber, where temperature can be varied through a programmed cycle, and thermal compensation factors generated for each individual sensor. The chart below shows typical data, both uncompensated and compensated output from a sensor with a stand off of 39.4 in. (1,000 mm). Compensation provides a dramatic improvement in temperature stability.