Illuminating or imaging samples from a broad angular range is essential in a wide variety of computational 3D imaging and resolution-enhancement techniques, such as optical projection tomography, optical diffraction tomography, synthetic aperture microscopy, Fourier ptychographic microscopy, structured illumination microscopy, photogrammetry, and optical coherence refraction tomography. The wider the angular coverage, the better the resolution enhancement or 3D-resolving capabilities. However, achieving such angular ranges is a practical challenge, especially when approaching
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Optical projection tomography (OPT) is a three-dimensional (3D) fluorescence imaging technique, in which projection images are acquired for varying orientations of a sample using a large depth of field. OPT is typically applied to a millimeter-sized specimen, because the rotation of a microscopic specimen is challenging and not compatible with live cell imaging. In this Letter, we demonstrate fluorescence optical tomography of a microscopic specimen by laterally translating the tube lens of a wide-field optical microscope, which allows for high-resolution OPT without rotating the sample. The cost is the reduction of the field of view to about halfway along the direction of the tube lens translation. Using bovine pulmonary artery endothelial cells and 0.1 µm beads, we compare the 3D imaging performance of the proposed method with that of the conventional objective-focus scan method.
more » « less- Award ID(s):
- 1808331
- NSF-PAR ID:
- 10412138
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 48
- Issue:
- 10
- ISSN:
- 0146-9592; OPLEDP
- Page Range / eLocation ID:
- Article No. 2623
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Spectroscopic microtomography provides the ability to perform 4D (3D structural and 1D chemical) imaging of a thick microscopic specimen. Here, we demonstrate spectroscopic microtomography in the short-wave infrared (SWIR) wavelength using digital holographic tomography, which captures both the absorption coefficient and refractive index. A broadband laser in tandem with a tunable optical filter allows us to scan the wavelength from 1100 to 1650 nm. Using the developed system, we measure human hair and sea urchin embryo samples. The resolution estimated with gold nanoparticles is 1.51 μm (transverse) and 1.57 μm (axial) for the field of view of 307 × 246 μm2. The developed technique will enable accurate and efficient analyses of microscopic specimens that have a distinctive absorption or refractive index contrast in the SWIR range.more » « less
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Optical projection tomography (OPT) is a powerful imaging modality for attaining high resolution absorption and fluorescence imaging in tissue samples and embryos with a diameter of roughly 1 mm. Moving past this 1 mm limit, scattered light becomes the dominant fraction detected, adding significant “blur” to OPT. Time-domain OPT has been used to select out early-arriving photons that have taken a more direct route through the tissue to reduce detection of scattered photons in these larger samples, which are the cause of image domain blur1. In addition, it was recently demonstrated by our group that detection of scattered photons could be further depressed by running in a “deadtime” regime where laser repetition rates are selected such that the deadtime incurred by early-arriving photons acts as a shutter to later-arriving scattered photons2. By running in this deadtime regime, far greater early photon count rates are achievable than with standard early photon OPT. In this work, another advantage of this enhanced early photon collection approach is demonstrated: specifically, a significant improvement in signal-to-noise ratio. In single photon counting detectors, the main source of noise is “afterpulsing,” which is essentially leftover charge from a detected photon that spuriously results in a second photon count. When the arrival of the photons are time-stamped by the time correlated single photon counting (TCSPC) module , the rate constant governing afterpusling is slow compared to the time-scale of the light pulse detected so it is observed as a background signal with very little time-correlation. This signal is present in all time-gates and so adds noise to the detection of early photons. However, since the afterpusling signal is proportional to the total rate of photon detection, our enhanced early photon approach is uniquely able to have increased early photon counts with no appreciable increase in the afterpulsing since overall count-rate does not change. This is because as the rate of early photon detection goes up, the rate of late-photon detection reduces commensurately, yielding no net change in the overall rate of photons detected. This hypothesis was tested on a 4 mm diameter tissue-mimicking phantom (μa = 0.02 mm-1, μs’ = 1 mm-1) by ranging the power of a 10 MHz pulse 780-nm laser with pulse spread of < 100 fs (Calmar, USA) and an avalanche photodiode (MPD, Picoquant, Germany) and TCSPC module (HydraHarp, Picoquant, Germany) for light detection. Details of the results are in Fig. 1a, but of note is that we observed more than a 60-times improvement in SNR compared to conventional early photon detection that would have taken 1000-times longer to achieve the same early photon count. A demonstration of the type of resolution possible is in Fig 1b with an image of a 4-mm-thick human breast cancer biopsy where tumor spiculations of less than 100 μm diameter are observable. 1Fieramonti, L. et al. PloS one (2012). 2Sinha, L., et al. Optics letters (2016).more » « less
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Abstract Advancements in three‐dimensional (3D) printing technology have the potential to transform the manufacture of customized optical elements, which today relies heavily on time‐consuming and costly polishing and grinding processes. However the inherent speed‐accuracy trade‐off seriously constrains the practical applications of 3D‐printing technology in the optical realm. In addressing this issue, here, a new method featuring a significantly faster fabrication speed, at 24.54 mm3h−1, without compromising the fabrication accuracy required to 3D‐print customized optical components is reported. A high‐speed 3D‐printing process with subvoxel‐scale precision (sub 5 µm) and deep subwavelength (sub 7 nm) surface roughness by employing the projection micro‐stereolithography process and the synergistic effects from grayscale photopolymerization and the meniscus equilibrium post‐curing methods is demonstrated. Fabricating a customized aspheric lens 5 mm in height and 3 mm in diameter is accomplished in four hours. The 3D‐printed singlet aspheric lens demonstrates a maximal imaging resolution of 373.2 lp mm−1with low field distortion less than 0.13% across a 2 mm field of view. This lens is attached onto a cell phone camera and the colorful fine details of a sunset moth's wing and the spot on a weevil's elytra are captured. This work demonstrates the potential of this method to rapidly prototype optical components or systems based on 3D printing.
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