RESUMO
With the rapid progress of advanced manufacturing, three-dimensional metrology techniques that are able to achieve nanometer spatial resolution and to capture fast dynamics are highly desired, for which a snapshot ability and a common-light-path setup are required. Commonly used off-axis holography and phase-shifting interferometry are short in fulfilling those requirements. We studied the suitability and performance of the coherent modulation imaging (CMI) method for metrology applications. Both transparent and reflective samples are measured in visible light experiments. Thanks to its ability to retrieve separate wavefronts at different wavelengths from a single measurement, CMI allows for attaining an enlarged range of measurement free from phase wrapping by utilizing the concept of synthetic wavelength. The CMI method fulfills well the requirements for advanced metrology and can be implemented at any wavelength. We expect it would be a powerful addition to the pool of advanced metrology tools.
RESUMO
Coherent diffraction imaging (CDI) is a rapidly advancing technique, especially for imaging weakly absorptive samples with x-rays or electrons at nano or atomic resolutions. For the study of fast dynamics, single-shot imaging ability is essential. However, reconstructions provided by current single-shot CDI methods are subject to the impairment of illumination artifacts. If one wants to obtain artifact-free object images, flat or well-calibrated illumination would be required. Here, we proposed an extension to coherent modulation imaging (CMI) to realize pure object function retrieval from a single sample measurement. This extension removes the restrictions on the forms of illumination and allows flexibly placing the object between the illumination aperture and the modulator. Our method has been verified in the numerical simulation and visible light experiment, and it could make CMI a practical and powerful microscopy technique.
