
B-64663EN/01 LASER FUNCTION 8.CONTROL FUNCTION
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8.1 OPTICAL PATH LENGTH COMPENSATION
Overview
The distance between the oscillator and the condensing lens varies as
the reflecting mirror moves along its axis (if there is one). The light
propagation distance at which a stable processing characteristic is
realized is generally limited to within a certain range. In a large
machine, in which the reflecting mirror has to move a long distance
exceeding such a limit because of its mechanical structure, it has been
conventionally impossible to maintain a stable characteristic over the
entire stroke. The optical path length compensation function is
developed to avert this problem. This function consists of an axis to
adjust the length of the optical path. If a move command is issued to
the reflecting mirror, the optical path adjustment axis is automatically
moved to keep the optical path length.
Function selection
When the option for optical path length compensation is specified,
resetting bit 1 (FMS) of parameter No. 15702 to "0" enables optical
path length compensation.
Mechanism to implement control
The mechanism described below is necessary to use optical path
length compensation.
1 Prepare an axis (called the U-axis) that enables the
beam-reflecting mirror block to move linearly in order to change
the light propagation distance.
2 Configure the U-axis so that moving the mirror block changes
the light propagation distance α (1 to 511) times as large as the
distance through which the mirror block moves.
3 Configure the U-axis so that its maximum speed is not lower than
1/α of the total rapid traverse rate of the axis along which the
optical path is changed.
4 Prepare a reference position for all axes including the U-axis.
The length of the optical path is calculated based on the reference
position.
5 Provide a measure to prevent interference between the U-axis
and any other axes.