Abstract
Moiré fringe is a traditional subdivision technique in precision displacement measurement. In general, use photodiode as
a four-segment sensor. In this paper, we'll introduce a new system for grating subdivision of moiré fringe. The system
consists of light source, condenser lens, grating, microscope tube, and CMOS image sensors. Different ways with the
traditional image acquisition, there is an angle θ between grating stripe and the optical axis of the microscope system.
Therefore, the stripe image which output by the CMOS image sensor becomes oblique. With different method of our
previous study, a virtual moiré will form by the oblique stripes superimposed with the CMOS image array, which using
digital image processing. The same as traditional method, the movement direction of the virtual moiré fringe is vertical
with the direction movement of grating in this system. The virtual moiré fringe will move a space with grating period,
the magnification has a relationship with the angle θ. Compare with early study, the largest increase for this system is
the average effect of grating measurement system will be fully utilized by virtual moiré formed by CMOS image array.
For the subdivision technique use the CMOS image array, system resolution will be large increased too. In this paper, the
details of system components will be introduced, the magnification relationship of grating period and tilt angle will be
discussed. It can be concluded that virtual moiré subdivision system performs better resolution and precision from
experiment results.
