Single-shot off-axis digital holographic system with extended field-of-view by using multiplexing method

Dual Field-of-View Off-Axis Spatially Multiplexed Digital Holography Using Fresnel's Bi-Mirror

Digital holography (DH) is an important method for three-dimensional (3D) imaging since it allows for the recording and reconstruction of an object's amplitude and phase information. However, the field of view (FOV) of a DH system is typically restricted by the finite size of the pixel pitch of the digital image sensor. We proposed a new configuration of the DH system based on Fresnel's bi-mirror to achieve doubling the camera FOV of the existing off-axis DH system which leveraged single-shot acquisition and a common-path optical framework. The dual FOV was obtained by spatial frequency multiplexing corresponding to two different information-carrying beams from an object. Experimental evidence of the proposed dual FOV-DH system's viability was provided by imaging two different areas of the test object and an application to surface profilometry by measuring the step height of the resolution chart which showed excellent agreement with an optical profiler. Due to the simple configuration, the proposed system could find a wide range of applications, including in microscopy and optical metrology.

Automotive tire defect characterization with a portable digital holographic camera with an extended field of view

Detection of tire defects is of prime importance for the on-road safety of vehicles. Hence, a quick non-invasive mechanism is required for frequent testing of tires in service as well as for quality checks of newly manufactured tires in the automotive industry. We propose a methodology based on the principle of double-exposure digital holographic interferometry, implemented with a portable digital holographic camera for successful detection and dimension measurement of tire defects. To implement the principle, mechanical load is applied to a tire to produce interferometric fringes by comparing the normal and stressed states of the tire surface. The defects in the tire sample are identified from discontinuities in the interferometric fringes. Quantitative analysis of the displacement of the fringes gives the dimensions of the defects. Some experimental results are presented, validated by a vernier caliper.