Scanlab RTC6 PCIe Board - Page 244

RTC6 boards
Doc. Rev. 1.0.21 en-US
8 Advanced Functions for Scan Head Control and Laser Control
244
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Thereafter, the output value is calculated from the
current output position by adding (for all spatial
directions) the product of the scaling factor and the
current counter value.
This correction takes place every 10 µs.
(1)
Notes
• set_fly_x and set_fly_y can be used in
combination for 1D as well as for
2D Processing-on-the-fly applications (for
example, an xy positioning stage), particularly for
separate or separable marking tasks in the real
Image Field.
• For continuous marking in the virtual Image Field,
SCANLAB recommends to preferably use
set_fly_2d, see Chapter 8.6.4 ”Compensating
2D Motions”, page 249.
Determining the Scaling Factors
The scaling factors can be determined
experimentally:
(1) Read out the counter start value by get_encoder.
(2) Start the movement.
(3) Stop the movement.
(4) Read out the counter end value by
get_encoder
(2)
.
(5) Measure the distance traveled in mm.
(6) Calculate the encoder increment i as follows:
(7) Calculate the scaling factors Scalex and Scaley
[in bits per count] as follows:
Whereby K is the calibration factor [in bits per
mm], see Chapter 7.3.2 ”Image Field Size and
Image Field Calibration”, page 167 and i is the
encoder increment from Step 6.
If the workpiece moves at a constant speed v
x
or
v
y
[in mm per second] and an encoder simulation
has been activated by simulate_encoder, then
the scaling factors are calculated as follows:
(8) Adjust the signs of the scaling factors according
to the movement direction.
(1) The encoder counters are signed 32-bit counters with
overflow (= after reaching the maximum (minimum)
counter value, counting continues at the minimum
(maximum) counter value).
(2) Alternatively, the counter start and end values can be
stored in a cache on the RTC6 PCIe Board by the
list command store_encoder and then retrieved from
there by the control command read_encoder.
i
counter end value counter start value–
distance travelled
--------------------------------------------------------------------
-----------------------------=
Scalex
K
i
x
----=
Scaley
K
i
y
----=
Scalex
K v
x

(1.000.000 counts / s)
----------------------------------------------------=
Scaley
K v
y

(1.000.000 counts / s)
----------------------------------------------------=