In situ retrieval and correction of aberrations in moldless lenses using Fourier ptychography

Abstract

Liquid droplets cured at low temperatures or using ultraviolet light are primary approaches for fabricating refractive lenses without molds. Until now the performance of moldless lens fabrication process relied heavily on this step to precisely control the shape of each liquid droplet. Hence, a major hurdle in lenses fabricated from liquid droplets is the large variability of droplet shapes because they are sensitive to small amounts of interfacial forces. The shape of the final droplet critically affects the imaging performance of the lenses and cannot be reversed easily. Here, we aim to overcome this hurdle by performing in situ aberration correction using Fourier ptychography techniques. We demonstrate, for the first time, that computational optics can reverse high amounts of optical aberrations in moldless lenses and achieve high resolution imaging. In terms of imaging resolution, we successfully increased the resolving power of low powered moldless elastomer lenses by almost three-fold, from a numerical aperture of 0.035 to 0.099. The computational approach directly elucidates the spatially varying wavefront aberrations from each lens using the same imaging system. This provides direct feedback of droplet lens fabrication techniques without the need for advanced wavefront correction methods. The application of computational imaging onto moldless lenses, using consumer digital imaging systems, lends itself to the global efforts in decentralising high resolution image intensive scientific tools to the wider community.

Review of bio-optical imaging systems with a high space-bandwidth product

“…4(c)] 15,80,[106][107][108][109][110][111] and the defocus of the sample 112,113 can be numerically corrected for, even under severe conditions. 94,114 Based on this principle, Chung et al 115 reported a Fourier ptychographic retinal imaging method that can correct for eye lens aberrations and thereby enable full-resolution imaging of the retina. Similarly, postacquisition digital refocusing can be used to extend the depth of field for imaging microfilters containing captured tumor cells, 97 96-well plate, 112 blood smear, 109 and pathological slides.…”

Fourier ptychography: current applications and future promises

“…Increased resolution/SBP Aperture synthesis [1,[21][22][23][24] Phase imaging Phase retrieval [25][26][27][28][29] Digital refocusing Phase retrieval [1,27,30] Aberration correction EPRY [24,[31][32][33] Long working distance low NA objective [34,35] Sub-λ imaging high-angle illumination [21][22][23]34,36,37] Multimodal imaging scanning illumination angle [24,34,38] High-speed LED & camera multiplexing [26,[39][40][41][42][43][44][45] Compact and portable Novel hardware [33,46,47] 3D imaging light field, 1st Born, multislice [48][49][50][51][52][53][54][55][56] computation using low numerical aperture (NA) op...…”

“…[31] for measuring and correcting for aberrations within the coherent transfer function from a standard FP data set. This capability has since allowed FP to be implemented with extremely aberrated lenses, such as moldless lenses [47] and mobile phone camera lenses [33] as shown in Fig. 9.…”

Raster adaptive optics for video rate aberration correction and large FOV multiphoton imaging

“…In laser scanning microscopes (LSM), the optical SBP is calculated by dividing the field of view (FOV) over the lateral point spread function (PSF) in a two-dimensional raster scan [3,6]. Hence, low SBP is attributed to non-uniform distribution of spatial aberrations across the entire FOV arising from either optical imperfections of optical elements across the entire system (system aberrations (SA)), imperfections towards the edges of the imaging FOV of a standard imaging objective lens (lens aberrations (LA)) [5,7,8] and/or sample-derived refractive index inhomogeneity (sample aberrations (SAA)) [9,10]. While customized objectives or scan lenses have extended the imaging FOV [3,6,11] to increase their SBP, they account only for optical distortion, which stem from field curvature of the lens, but not distortion caused by the sample.…”