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Single- and Dual-Axis Scanning Galvo Systems for Small Beam Diameters
Appendix C Reasons For Image Distortion
The deflection of a laser beam with a two-mirror system results in three effects:
(1) The arrangement of the mirrors leads to a certain distortion of the image field –
see Fig. C.1 below.
Fig. C.1 Field Distortion in a Two-way Mirror Deflection System
This distortion arises from the fact that the distance between mirror 1 and the image
field depends on the size of the mechanical scan angles of mirror 1 and mirror 2. A
larger scan angle leads to a longer distance.
(2) The distance in the image field is not proportional to the scan angle itself, but to
the tangent of the scan angle. Therefore, the marking speed of the laser focus in the
image field is not proportional to the angular velocity of the corresponding scanner.
(3) If an ordinary lens is used for focusing the laser beam, the focus lies on a sphere.
In a flat image field, a varying spot size results.
Beam In
Scanner 1
Scanner 2
Ø2
Ø1
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