A three-wavelength-converted light source based on patterned quantum dot film fabricated by a photolithographic process and blue led was proposed to on-axis multi-wavelength digital holography. A patterned quantum dot film was fabricated based on a photolithographic process. Each process was executed based on quantum dot particles-SU8 photoresist mixture. To improve the conversion efficiency of a quantum dot film, TiO2 film was also patterned among quantum dot films as a role of scattering barrier. From the experiment result, a stepped object with 1.8µm height was reconstructed, and amplified noise could be suppressed from 88nm to 19nm.
Digital holography (DH) has become a promising tool in various research fields for acquiring quantitative phase information (QPI). However, its reliance on high-coherence light sources such as lasers often leads to speckle noise, which degrades image quality. Although low-coherence sources like light-emitting diodes (LEDs) can mitigate this noise, they struggle to create complete interference patterns for specimens with optical path differences exceeding their coherence length. This trade-off between high coherence and low speckle noise presents a significant challenge in DH, particularly in applications requiring long coherence lengths for accurate QPI. Our research addresses this challenge with an AIpowered approach. By training an AI model with paired hologram data from lasers and LEDs operating at the same peak wavelength, we have developed a method to reduce speckle noise while preserving the coherence length. The newly proposed method has been verified on reflective specimens using a Michelson interferometer. The resulting holograms from this AI model exhibit clear interference patterns over depths that match the laser’s coherence length, while simultaneously achieving significantly reduced speckle noise, akin to that observed in LED holography.
To Improve axial resolution of digital holographic microscopy, we optimized the light source based on the patterned quantum dots (QDs) film with blue LED. We tried to pattern the QDs laterally as a 2-D patterned QD film by photolithography and micro imprinting process to improve color conversion efficiency of QDs as well as keep narrow bandwidth, resulting in enhancing the optical intensity and axial resolution. Using the additional optical edge filters and relay optics, newly proposed light source of digital holography microscopy for QPI has resulted in the enhanced axial resolution to1.8μm and the increased optical signal.
We presented the digital holography (DH) system with enhanced image quality. While conventional DH uses highcoherence laser for illuminations, the speckle noise included in the image degrades the quality of the reconstructed data. To reduce the noise regards to the light source, lower-coherence light source could be applied in DH system. In this paper, the quantum dot (QD) based wavelength converter is utilized as the light source. Compared with light-emitting diode (LED), QD-based light source could be applied to versatile system, including dual-wavelength DH. Due to the low coherence both temporally and spatially, spatial filtering and collimation is presented. Also, numerical processes including noise reduction and aberration compensation is described to enhance the quality of the image. By experimental verifications, the proposed DH system shows better quality compared with conventional system, which is enough to utilize the quantitative measurement.
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