Determination of point-spread function of paper substrate based on light-scattering simulation

Modrić, Damir; Maretić, Katja Petric; Hladnik, Aleš

doi:10.1364/ao.53.007854

“…7. However, scattering within paper is expected to further broaden the light distribution at the confocal pinhole with its own point spread function, which has been shown to approximately follow a Lorentzian function [50] (see dashed lines in Fig. 7).…”

Section: Resultsmentioning

confidence: 99%

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

Mozaffari¹,

Larocca²,

Jaedicke³

et al. 2020

Biomed. Opt. Express

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Visualizing and assessing the function of microscopic retinal structures in the human eye is a challenging task that has been greatly facilitated by ophthalmic adaptive optics (AO). Yet, as AO imaging systems advance in functionality by employing multiple spectral channels and larger vergence ranges, achieving optimal resolution and signal-to-noise ratios (SNR) becomes difficult and is often compromised. While current-generation AO retinal imaging systems have demonstrated excellent, near diffraction-limited imaging performance over wide vergence and spectral ranges, a full theoretical and experimental analysis of an AOSLO that includes both the light delivery and collection optics has not been done, and neither has the effects of extending wavefront correction from one wavelength to imaging performance in different spectral channels. Here, we report a methodology and system design for simultaneously achieving diffraction-limited performance in both the illumination and collection paths for a wide-vergence, multi-spectral AO scanning laser ophthalmoscope (SLO) over a 1.2 diopter vergence range while correcting the wavefront in a separate wavelength. To validate the design, an AOSLO was constructed to have three imaging channels spanning different wavelength ranges (543 ± 11 nm, 680 ± 11 nm, and 840 ± 6 nm, respectively) and one near-infrared wavefront sensing channel (940 ± 5 nm). The AOSLO optics and their alignment were determined via simulations in optical and optomechanical design software and then experimentally verified by measuring the AOSLO's illumination and collection point spread functions (PSF) for each channel using a phase retrieval technique. The collection efficiency was then measured for each channel as a function of confocal pinhole size when imaging a model eye achieving near-theoretical performance. Imaging results from healthy human adult volunteers demonstrate the system's ability to resolve the foveal cone mosaic in all three imaging channels despite a wide spectral separation between the wavefront sensing and imaging channels.

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“…In the absence of scattering effects, the spatial profile of the light incident on the confocal pinhole is expected to follow that of the double-pass point spread function's encircled energy [29], which follows the black curve on Figure 7. However, scattering within paper is expected to further broaden the light distribution at the confocal pinhole with its own point spread function, which has been shown to approximately follow a Lorentzian function [30] (see dashed lines in Figure 7). To measure the paper's scattering point spread function, a separate simplified setup with the same illumination profile and model eye from the AOSLO was used to measure the collection efficiency per imaging channel vs confocal pinhole size (see dense dotted lines in Figure 7).…”

Section: Resultsmentioning

confidence: 99%

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

Mozaffari

¹

,

Larocca

²

,

Jaedicke

³

et al. 2020

Preprint

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Visualizing and assessing the function of microscopic retinal structures in the human eye is a challenging task that has been greatly facilitated by ophthalmic adaptive optics (AO). Yet, as AO imaging systems advance in functionality by employing multiple spectral channels and larger vergence ranges, achieving optimal resolution and signal-to-noise ratios (SNR) becomes difficult and is often compromised. While current-generation AO retinal imaging systems have demonstrated excellent, near diffraction-limited imaging performance over wide vergence and spectral ranges, a full theoretical and experimental analysis of an AOSLO that includes both the light delivery and collection optics has not been done, and neither has the effects of extending wavefront correction from one wavelength to imaging performance in different spectral channels. Here, we report a methodology and system design for simultaneously achieving diffraction-limited performance in both the illumination and collection paths for a wide-vergence, multi-spectral AO scanning laser ophthalmoscope (SLO) over a 1.2 diopter vergence range while correcting the wavefront in a separate wavelength. To validate the design, an AOSLO was constructed to have three imaging channels spanning different wavelength ranges (543 ± 11 nm, 680 ± 11 nm, and 840 ± 6 nm, respectively) and one near-infrared wavefront sensing channel (940 ± 5 nm). The AOSLO optics and their alignment were determined via simulations in optical and optomechanical design software and then experimentally verified by measuring the AOSLO's illumination and collection point spread functions (PSF) for each channel using a phase retrieval technique. The collection efficiency was then measured for each channel as a function of confocal pinhole size when imaging a model eye achieving near-theoretical performance. Imaging results from healthy human adult volunteers demonstrate the system's ability to resolve the foveal cone mosaic in all three imaging channels despite a wide spectral separation between the wavefront sensing and imaging channels.

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“…These layers can be considered as separate areas in which the optical properties differ significantly. This resulted with the determination of point spread function of paper substrate based on light-scattering simulation with the clear indication of Lorentzian function as the one that satisfactorily describes the shape of the PSF (Modrić, Maretić & Hladnik, 2014). Itrić et al experimentally determined the PSF of the paper substrate and confirmed superiority of Lorentzian function for the description of the shape of the PSF, which was recently acknowledged by Rogers et al (2019).…”

mentioning

confidence: 92%

Determining point spread function of pressure sensitive labels facestock

Itrić¹,

Jakopčević²,

Kovačević³

et al. 2022

Proceedings - The Eleventh International Symposium GRID 2022

0

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Pressure sensitive labels (PSL) are a growing part of graphic industry. In the past, their design and application were rather limited to basic packaging and product information while currently labels are receiving more and more attention because they are customer's first contact with a product. PSL composition includes release liner, adhesive and facestock. Facestock can be considered as the most important part of the label since its properties determine the final label appearance. Nowadays, facestock material can be both paper and filmic. Therefore, it is necessary to perform a comprehensive characterization of pressure sensitive labels facestock in order to investigate the future impact of optical dot gain on the print. Point spread function is a measure of scattering and absorption of light in the given substrate. It carries information regarding paper composition and its future behaviour in term of optical dot gain. In the study, seven different facestock substrates were examined, two made from biogenic polyethylene, and five paper based PSL facestocks, three of which are made from 15% agro industrial waste by-products (barley, citrus and grape). Point spread function of the substrates were obtained by projecting collimated red laser light source on the facestock of pressure sensitive labels. Although the laser light used in this experiment was characterized by a narrow beam width of 0.5 mm and low divergence, <1 mrad, the beam was further converged and then passed through a space filter to ensure collimation of the laser beam which was then incident perpendicular to the set sample. Laser profile was firstly obtained by photodiode profiling. Based on the measured values of light intensity, the laser light profile was determined, as well as the average beam width that was needed for further image analysis. Image of the light scattering within the substrate was obtained perpendicular to the surface with Canon EOS 5DS camera. From the obtained image, laser profile was removed, and the resulting profile gives the point spread function of the substrate. The resulting images were processed with commercially available image analysis software (ImageJ). The mean background intensity subtracted from each individual pixel was determined to remove the background effect, and the distribution of the scattered light profile was achieved. The results showed that facestock composition has a high influence on PSF shape and width.

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Determination of point-spread function of paper substrate based on light-scattering simulation

Cited by 11 publications

References 22 publications

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

Wide-vergence, multi-spectral adaptive optics scanning laser ophthalmoscope with diffraction-limited illumination and collection

Determining point spread function of pressure sensitive labels facestock

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