Experimental investigations and parametric studies of surface roughness measurements using spectrally correlated speckle images

Breaking the diffraction limit in imaging microscopes with far-field imaging options has always been the thrust challenge for optical engineers and biologists over the years. Although structured illumination microscopy and Bessel beam assisted imaging has shown the capability of imaging with sub-diffraction resolutions, they rely on the use of objective lenses with large numerical apertures (NA). Hence, they fail to sustain resolutions at larger working distances. In this context, we demonstrate a method for nanoscale resolution imaging at longer working distances, named as Structured Illumination Bessel Microscopy (SIBM). The proposed method is envisaged for both biological and engineering applications that necessitate high imaging resolutions at large working distances.

Driven by high strength‐to‐weight ratios and advanced design flexibility, the application of composite structures in the aerospace industry is growing exponentially. A low thermal conductivity and thermal expansion coefficient give an edge when it comes to applications requiring stringent thermal loads, especially in aircraft engines. It is thus necessary to characterize, qualitatively and quantitatively, the behaviour of composite structures under harsh thermal loads for their certification. In this paper, characterization of multiple heat damages on 30 × 30 cm2 composite panels (16 layers, 00 unidirectional, and carbon fibre composite panel) is carried out by using visual inspection, ultrasound (a‐ and c‐scans), and shearography. It has been observed that shearography, being a fast and noncontact technique, offers multiple advantages for sizing thermal damages. Primarily, it could be applied as a technique for a quick and effective inspection of composites, in turn, increasing the productivity of the quality assurance cycle.

Design and simulation of GRIN objective lenses for an imaging fiber based speckle metrology system. Second International Seminar on Photonics, Optics, and Its Applications

In manufacturing engineering the surface finish of a machined component is of fundamental importance in order to ensure its performance. A non-contact and non-destructive device based on optical technique, is a promising alternative to stylus based device for carrying out measurement of surface quality. In addition to this, in situ monitoring of surface roughness on a workpiece is an important requirement in modern machining process, since it would increase on-line machining rate and consequently productivity. Here, measurement approaches and system configuration for surface roughness measurement using laser speckle intensity and contrast are discussed. The technique would allow full-field measurement over sample of interest having both rough and shiny surface properties. Measurement data on standard calibration plates is presented with details on the measurement accuracy and reliability.