• Universitat de València

Lensless holographic microscopes provide medium/high-resolution, low-noise, three-dimensional imaging with extended depth of field, at a lower price and size than their lens-based counterparts. However, these devices are mainly oriented towards laboratories and research centres, which require highly qualified technical personnel for their use. They are only applicable to a certain type of samples (low diffractive or essentially transparent objects with low density), which limits their range of applicability. Besides, with inline holography, when reconstructing the hologram, a double image of the object is generated, which is a problem associated with the noise and resolution of the reconstructed image. In the state of the art, there are some methods of minimisation of such a double image such as the "phase-shifting" method, iteration algorithms between twin images, partial coherence, digital post-processing, etc. However, new, more user-friendly online hologram reconstruction methods are needed to solve the technical problem of double imaging, to improve the quality of the final image and to be applicable to more sample types, including dynamic samples.

Researchers at the Universitat de València have developed a novel holographic microscope and holographic reconstruction method based on inline lensless microscopy, which allows quantitative phase measurement, eliminates double imaging and obtains an image with optimum resolution. The user-friendly device is based on the simultaneous emission of at least three wavelengths, and has a polychromatic sensor for recording the multiple hologram in a single exposure. The digital processing incorporates a weighted mixture of spectra, which improves the quality of the final image obtained, both in terms of noise and resolution. The device can be designed for use in both research and non-specialised centres and is applicable to the analysis of dynamic samples.

Several sectors of life and material sciences including biomedical applications, e.g. particle and cell counting, in the analysis of life cycles, morphology and motility of biological samples, in real-time tracking of samples, and in the characterisation and phase measurement of samples, in microfluidic applications; and in particular human and veterinary andrology.

The main benefits of the invention are:

• Elimination of the double image of the holography and obtaining a high quality final image.
• Real-time quantitative phase measurement for dynamic samples.
• Reduced hardware costs for quantitative phase imaging compared to conventional holographic microscopes.
• Imaging of bulk samples with expanded depth of field since no scanning of the sample is required.

• Patent granted