Optical Access Schemes for High Speed and Spatial Resolution Optical Absorption Tomography in Energy Engineering

Abstract

Optical diagnostic techniques play an important role in the engineering of modern energy processes. Optical absorption tomography as a diagnostic technique allows imaging of chemical species in flows with spatio-temporal resolution. The optical access scheme employed to acquire the tomographic projections impacts the limiting spatial resolution and imaging speed of the instrument. Our review of conventional optical access schemes indicates that there currently exist no practical schemes that can achieve simultaneous high-speed, high-spatial resolution imaging. Here, we show that advanced solid-state beam deflectors can be used to realize such a system. We evaluated a state-of-the-art electro-optic deflector combining a multi-pass scheme in a space-charged crystal and found that it can achieve a full deflection angle of 216 mrad (12.4°) at 90-kHz scan rate. We present how optical access schemes based on electro-optic deflectors can be arranged, estimating the increased bandwidth requirement for the data acquisition system. Using an existing tomography system and an image reconstruction algorithm, we show by simulation that the spatial resolution under non-optimum conditions can be improved by 38%. We describe in detail our implementation of the spatial resolution quantification algorithm. Our results demonstrate how advances in other disciplines can be exploited to further improve the performance of an optical tomography instrument. We anticipate our assay to motivate further development of optical access schemes as well as optimized image reconstruction algorithms.