  Large field-of-view (FOV) microscopic imaging with high lateral resolution
(1-2 microns for high space-bandwidth product) plays a pivotal role in
biomedicine and biophotonics, especially within the label-free regime, e.g.,
for whole slide tissue quantitative analysis and live cell culture imaging. In
this context, lensless digital holographic microscopy (LDHM) holds substantial
promise. However, one intriguing challenge has been the fidelity of
computational quantitative phase imaging (QPI) with LDHM in large FOV. While
photonic phantoms, 3D printed by two-photon polymerization (TPP), have
facilitated calibration and verification in small FOV lens-based QPI systems,
an equivalent evaluation for lensless techniques remains elusive, compounded by
issues such as twin-image and beam distortions, particularly towards the
detector edges. To tackle this problem, we propose an application of TPP over
large area to examine phase consistency in LDHM. In our research, we crafted
widefield calibration phase test targets, fabricated them with galvo and piezo
scanning, and scrutinized them under single-shot twin-image corrupted
conditions and multi-frame iterative twin-image minimization scenarios. By
displacing the structures toward the edges of the sensing area, we verified
LDHM phase imaging errors across the entire field-of-view, showing less than 12
percent of phase value difference between investigated areas. Interestingly,
our research revealed that the TPP technique, following LDHM and Linnik
interferometry cross-verification, requires novel design considerations for
successful large-area precise photonic manufacturing. Our work thus unveils
important avenues toward the quantitative benchmarking of large FOV lensless
phase imaging, advancing our mechanistic understanding of LDHM techniques and
contributing to their further development and optimization of both phase
imaging and fabrication.
