T. Agbana
Delft University of Technology
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by T. Agbana.
Optics Letters | 2017
T. Agbana; Hai Gong; Abena S. Amoah; Vitaly Bezzubik; Michel Verhaegen; Gleb Vdovin
We have shown that the maximum achievable resolution of an in-line lensless holographic microscope is limited by aliasing and, for collimated illumination, cannot exceed the camera pixel size. This limit can be achieved only when the optimal conditions on the spatial and temporal coherence state of the illumination are satisfied. The expressions defining the configuration, delivering maximum resolution with given spatial and temporal coherence of the illumination, are obtained. The validity of these conditions is confirmed experimentally.
Optics Letters | 2017
Hai Gong; T. Agbana; Paolo Pozzi; Oleg Soloviev; Michel Verhaegen; Gleb Vdovin
In this Letter, we show that a Shack-Hartmann wavefront sensor can be used for the quantitative measurement of the specimen optical path difference (OPD) in an ordinary incoherent optical microscope, if the spatial coherence of the illumination light in the plane of the specimen is larger than the microscope resolution. To satisfy this condition, the illumination numerical aperture should be smaller than the numerical aperture of the imaging lens. This principle has been successfully applied to build a high-resolution reference-free instrument for the characterization of the OPD of micro-optical components and microscopic biological samples.
PLOS ONE | 2018
T. Agbana; Jan-Carel Diehl; Fiona J. A. van Pul; Shahid M. Khan; Vsevolod Patlan; Michel Verhaegen; Gleb Vdovin
We have optimized the design and imaging procedures, to clearly resolve the malaria parasite in Giemsa-stained thin blood smears, using simple low-cost cellphone-based microscopy with oil immersion. The microscope uses a glass ball as the objective and the phone camera as the tube lens. Our optimization includes the optimal choice of the ball lens diameter, the size and the position of the aperture diaphragm, and proper application of immersion, to achieve diagnostic capacity in a wide field of view. The resulting system is potentially applicable to low-cost in-the-field optical diagnostics of malaria as it clearly resolves micron-sized features and allows for analysis of parasite morphology in the field of 50 × 50 μm, and parasite detection in the field of at least 150 × 150 μm.
european quantum electronics conference | 2017
Caterina Taballione; T. Agbana; Gleb Vdovine; Marcel Hoekman; Lennart Wevers; Jeroen Kalkman; Michel Verhaegen; Peter J. M. van der Slot; Klaus J. Boller
Wavelength meters are central for many applications such as in telecommunication systems [1] or laser monitoring [2]. The primary function of a wavelength meter is to provide an output signal that changes sensitively with the wavelength of the input light. Of central importance is the reproducibility of the output signal over long time intervals during which external perturbations might negatively affect the reproducibility of the displayed wavelengths.
Proceedings of SPIE | 2017
Caterina Taballione; T. Agbana; Gleb Vdovin; Marcel Hoekman; Lennart Wevers; Jeroen Kalkman; Michel Verhaegen; Peter J. M. van der Slot; K.-J. Boller
We present an integrated optical wavelength meter based on a Si3N4/SiO2 micro ring resonator (operating over a free spectral range of ≈ 2.6 nm) whose output response is immune to temperature changes. The wavelength meter readout is performed by a neural network and a non-linear optimization algorithm. This novel approach ensures a high wavelength estimation precision (≈ 50 pm). We observe a long-term reproducibility of the wavelength meter response over a time interval of one week. We investigate the influence of the ambient temperature on the estimated wavelength. We observe an immunity of the displayed output wavelength to temperature changes of up to several degrees. The temperature-drift immunity appears to be caused by deviations from the theoretically expected (perfect) transmission function of a ring resonator, i.e., caused by deviations that are usually undesired in spectroscopic devices.
Proceedings of SPIE | 2016
T. Agbana; Huizhen Yang; Oleg Soloviev; Gleb Vdovin; Michel Verhaegen
This paper presents experimental results of a static aberration control algorithm based on the linear relation be- tween mean square of the aberration gradient and the second moment of point spread function for the generation of control signal input for a deformable mirror (DM). Results presented in the work of Yang et al.1 suggested a good feasibility of the method for correction of static aberration for point and extended sources. However, a practical realisation of the algorithm has not been demonstrated. The goal of this article is to check the method experimentally in the real conditions of the present noise, finite dynamic range of the imaging camera, and system misalignments. The experiments have shown strong dependence of the linearity of the relationship on image noise and overall image intensity, which depends on the aberration level. Also, the restoration capability and the rate of convergence of the AO system for aberrations generated by the deformable mirror are experi- mentally investigated. The presented approach as well as the experimental results finds practical application in compensation of static aberration in adaptive microscopic imaging system.
Proceedings of SPIE | 2015
T. Agbana; Oleg Soloviev; Vitalii V. Bezzubik; Vsevolod Patlan; Michel Verhaegen; Gleb Vdovin
We have implemented an extended depth of field optical system by wavefront coding with a micromachined membrane deformable mirror. This approach provides a versatile extension to standard wavefront coding based on fixed phase mask. First experimental results validate the feasibility of the use of adaptive optics for variable depth wavefront coding in imaging optical systems.
Physics@FOM Veldhoven 2018 | 2018
Caterina Taballione; Meryem Benelajla; T. Agbana; G. Vdovine; Marcel Hoekman; Lennart Wevers; Jeroen Kalkman; M. Verhagen; P.J.M. van der Slot; Klaus J. Boller
european quantum electronics conference | 2017
Caterina Taballione; T. Agbana; G. Vdovine; Marcel Hoekman; Lennart Wevers; Jeroen Kalkman; Michel Verhaegen; Petrus J.M. van der Slot; Klaus J. Boller
19th European Conference on Integrated Optics, ECIO 2017 | 2017
Caterina Taballione; T. Agbana; G. Vdovine; Marcel Hoekman; Lennart Wevers; Jeroen Kalkman; Michel Verhaegen; Petrus J.M. van der Slot; Klaus J. Boller