Comparative study of cost effective laser and DLP projectors for fringe projection

Abstract

Fringe projection using a digital video projector is extensively used in high-speed 3D optical metrology. However, low-cost commercially-available projectors are susceptible to gamma non-linearity, lack of depth of field, system vibration and noise, which distorts the fringe patterns and introduces significant errors in the phase measurements. In this work, we compare a low-cost DLP and a laser projector in terms of gamma performance (Figure 1) and depth of focus (Figure 2), and assess which projector type performs better for fringe projection applications. Our study finds that the focus-free eye-safe laser projector provides more consistent high-quality sinusoidal fringe patterns and has a much longer depth of focus. Thus, a laser projector is recommended for practical implementation in cost-effective fringe projection systems with the potential to be used for a range of measured objects due to the much longer depth of focus. Figure 1. Non-linear gamma curve. (a) Laser projector, (b) DLP projector. Figure 2. Schematic illustration of depth of focus setup.