4.5 Measurement with Two Measuring Units
To perform dual measurement with a combination of two measuring units, each
measuring unit must have been optically aligned.
Refer to “4.3 Optical Axis Alignment” for more information.
Also note that the appropriate considerations must be taken into account according
to the type of dual measurement, DXY type or DF type.
4.5.1 DXY type
If a workpiece with a high-reflection coefficient is
measured with two measuring units being
completely crossed (in a DXY-type setup), the
scanning beam from one measuring unit will be
reflected into the reception window of the other
measuring unit, reducing the measuring accuracy.
An arrangement is required in such a case so that
the light from one measuring unit will not be
reflected from the workpiece into the reception
window of the counterpart measuring unit.
Light from the Y-axis
reflected to the X-axis.
Y-axis
isX-ax
(1) Arrangement to provide a step
L
is
Y-axi
As shown on the right, arrange a step of L
between the X axis and the Y axis.
The step L should not be smaller than 10 mm.
X-ax
(2) Arrangement to provide an angle
As shown on the right, arrange an angle θ
between the X axis and the Y axis.
The angle θ should not be smaller than 15 degrees
or 0.25 radians.
Y-axis
X-axis
θ
No. 99MBC094A
4-6
