4 DESIGNING THE FIXTURES
This chapter describes precautions to be observed when attaching
the emission unit and the reception unit, which have been detached
from the support base of the measuring unit, to a specially arranged
dedicated fixture.
4
4.1 Outline
In application, the emission unit and the reception unit may have to be detached from the
support base of the measuring unit and attached to a dedicated fixture. If this is the case,
the measuring accuracy cannot be ensured unless the emission unit and the reception unit
are properly aligned on the dedicated fixture. Design a proper fixture according to this
section.
4.2 Consideration to Calibration
To ensure accurate measurements, design the fixture so that the workpiece to be
measured can be positioned at the point of measurement that is the focal point of the
emission unit. Also, make allowances for calibration and for a calibration gage to be
mounted on the fixture.
4.2.1 Measuring position and resulting accuracy
As shown in the figure below, the scanning beam of the measuring unit is produced by
reducing the thick beam to a beam of the minimum diameter at the measuring position that
is the focal point.
However, since the inclination of the reception signal is defined as “beam
diameter/scanning speed”, the inclination will be the steepest at measuring point (b) and will
be less steep at points (a) and (c), off from the measuring point.
The less steep the inclination of the reception signal, the more susceptible the signal is to
noise and light disturbance, resulting in degraded repeatability. Thus, due attention should
be paid to ensure that the workpiece is located at the measuring position.
Measuring position that is focal point.
Inclination of the reception
Measuring region
Emission unit side
（ａ） （ｂ） （ｃ）
Reception unit side
No. 99MBC094A
4-1
