28
13.
Technical explanation
Distortion correction pattern
Since the silicon substrate of LCOS-SLM is extremely thin compared to the glass substrate, it is
difficult to maintain it in a perfect plane, and initial shape distortion of several [µm] remains. Therefore,
when a plane wave is made incident to emit the plane wave, the remaining distortion of the silicon
substrate, which is the mirror surface, causes wavefront distortion as shown in Fig. 22.
Fig.22
Deformation of the output wavefront due to LCOS-SLM distortion
The distortion correction pattern corrects wavefront distortion caused by distortion of the silicon
substrate. The distortion correction pattern is designed to represent the reverse distortion of the
silicon substrate in liquid crystal. By adding the distortion correction pattern to the desired phase
pattern, an aberration-free result is obtained.
Silicon backplane
Glass substrate
Plane wave
Output wave
Dielectric multi-layer mirror
