Lens-free imaging (LFI) has become an important microscopy tool in many life science and industrial applications. Due to the absence of optical lenses (such as objectives) and accompanying lens aberrations (such as chromatic aberrations), the LFI modality is well suited for optical inspection of microscopic objects in a wide spectral range. However, the relatively restricted spectral sensitivity of CMOS imagers, i.e. from visible (~400 nm) up to near-infrared range (~900 nm), limits the wide spectral use of the technique. Many microscopic samples contain valuable information both in the visible and in the short wave infra-red (SWIR), sometimes in addition to visible (VIS) and near-infrared (NIR). With the recent emergence of cost-effective image sensor technologies such as quantum-dot and graphene-based image sensors with high quantum efficiency in SWIR, new lens-free imaging opportunities are emerging for wideband and high throughput microscopy. We demonstrate for the first time an LFI system based on a quantum-dot image sensor, capable of operating in both the visible and short-wave infrared range. The holograms of the samples are obtained through multiple partially coherent illumination sources in both visible and short-wave infrared (ranging from 405 nm to 1550 nm). The captured holograms are reconstructed to obtain images of the sample in focus. We demonstrate an optical resolution of 3.48 micron in a field of view of 9.6 mm2 over the whole spectral range. Our technique mitigates the need for bulky and expensive achromatic imaging optics and offers significant improvements in cost, field-of-view, scalability, and optical resolution to achieve microscopic imaging in both the visible and short-wave infrared spectral range with a simple imaging system. We present in this paper a performance analysis of the system and several potential applications and use cases.
Lens-free holographic microscopy (LHM) is a promising imaging technique for life science and industrial applications, yet system miniaturization and cost reduction without compromising imaging performance remain challenging for field applications in low-resource settings. We demonstrate a cost-effective LHM system without needs for precision optical and mechanical parts (such as lenses, beam-splitters, or kinematic stages) and relies solely on robust optoelectronic hardware and software co-design for high performance imaging. The compact and lightweight form-factor is achieved through integration of light sources, an image sensor and all control electronics with automated calibration and multiwavelength reconstruction algorithms. Amplitude and phase images of a sample can be reconstructed in a few seconds with a micron level optical resolution in a field-of-view of 16.5 mm2. The method offers a portable and scalable solution for microscopic imaging applications.
Oblique Plane Microscopy (OPM) is a light sheet microscopy technique that combines oblique illumination with
correction optics that tilt the focal plane of the collection system. OPM can be used to image conventionally mounted
specimens on coverslips or tissue culture dishes and has low out-of-plane photobleaching and phototoxicity. No moving
parts are required to achieve an optically sectioned image and so high speed optically sectioned imaging is possible. The
first OPM results obtained using a high NA water immersion lens on a commercially available inverted microscope
frame are presented, together with a measurement of the achievable optical resolution.