An optimized optical system for backlit imaging

Ghandhi, J. B.; Heim, Douglas

doi:10.1063/1.3128728

Cited by 34 publications

(18 citation statements)

References 2 publications

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“…The original diffused illumination source used at SNL [3,11] followed the design of Ghandi and Heim [12], and this configuration was also implemented in the DBIEI measurements presented here from UPV; however, a new optical configuration characterized by a much larger region of spatial uniformity and more diffused rays at the imaging plane has been developed at SNL as described in Westlye et al [13]. The improved optical setup reduces perceived attenuation due to beam steering.…”

Section: Diffused Back-illumination Extinction Imaging (Dbiei)mentioning

confidence: 99%

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

Skeen

Manin

Pickett

et al. 2016

SAE Int. J. Engines

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The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unpublished work from prior ECN workshops is reviewed. Experiments measuring soot particle size and morphology, soot volume fraction (fv), and transient soot mass have been conducted at various international institutions providing target data for improvements to computational models. Multiple modeling contributions using both the Reynolds Averaged Navier-Stokes (RANS) Equations approach and the Large-Eddy Simulation (LES) approach have been submitted. Among these, various chemical mechanisms, soot models, and turbulence-chemistry interaction (TCI) methodologies have been considered

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Section: Diffused Back-illumination Extinction Imaging (Dbiei)mentioning

confidence: 99%

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

Skeen

Manin

Pickett

et al. 2016

SAE Int. J. Engines

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“…To enhance light throughput relative to prior techniques for applications requiring high-temporal resolution, Ghandhi and Heim [3] used a small (25 mm) engineered diffuser to generate a specified output radiant intensity distribution from a collimated input. The diffused light was collected by a large Fresnel lens and redirected through the region of interest toward the collection optics.…”

Section: A Review Of Previous Optical Solutions For Extinction Imagingmentioning

confidence: 99%

“…As will be discussed below, specific measurement targets include the transient liquid length and soot formation in fuel sprays. To meet this need, a diffused back-illumination extinction imaging (DBIEI) system, inspired by the Ghandhi and Heim [3] setup, has been used by a number of institutions participating in the Engine Combustion Network (ECN) [4][5][6][7]. DBIEI has been used to measure the liquid length of diesel sprays from a set of shared injectors.…”

Section: Introductionmentioning

confidence: 99%

Diffuse back-illumination setup for high temporally resolved extinction imaging

et al. 2017

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This work presents the development of an optical setup for quantitative, high-temporal resolution line-of-sight extinction imaging in harsh optical environments. The application specifically targets measurements of automotive fuel sprays at high ambient temperature and pressure conditions where time scales are short and perceived attenuation by refractive index gradients along the optical path (i.e., beam steering) can be significant. The illumination and collection optics are optimized to abate beam steering, and the design criteria are supported by well-established theoretical relationships. The general effects of refractive steering are explained conceptually using simple ray tracing. Three isolated scenarios are analyzed to establish the lighting characteristics required to render the observed radiant flux unaffected by the steering effect. These criteria are used to optimize light throughput in the optical system, enabling minimal exposure times and high-temporal resolution capabilities. The setup uses a customized engineered diffuser to transmit a constant radiance within a limited angular range such that radiant intensity is maximized while fulfilling the lighting criteria for optimal beam-steering suppression. Methods for complete characterization of the optical system are detailed. Measurements of the liquid-vapor boundary and the soot volume fraction in an automotive spray are presented to demonstrate the resulting improved contrast and reduced uncertainty. The current optical setup reduces attenuation caused by refractive index gradients by an order of magnitude compared to previous high-temporal resolution setups.

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“…For this purpose, optics combining non-spherical lenses 9 and that using diffuser 10 have been reported. However, the severe requirement in alignment is needed for the former because of the complex shapes of the nonspherical lenses, and for the latter optics, there has been an issue in uniformity of illumination on a target.…”

Section: Transmitting Opticsmentioning

confidence: 99%

Development of long range, real-time, and high resolution 3D imaging ladar

et al. 2011

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In the previous study, we have introduced the concept of the real-time 3D imaging LADAR (LAser Detection And Ranging) using linear array receiver. In this paper, we demonstrate a long range, high resolution, and high speed 3D imaging using the developed system. The system consists of in-house-made key components. The linear array receiver consists of the previously reported APD array and the ROIC array assembled in one package. We newly developed the transmitting optics using pupil divide method which realizes a uniform illumination on a target. By combining these devices with the one dimensional fast scanner, we realized a 256 × 256 pixels range imaging with a on-line frame rate of more than 10 Hz at a distance of more than 1 km.

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An optimized optical system for backlit imaging

Cited by 34 publications

References 2 publications

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

A Progress Review on Soot Experiments and Modeling in the Engine Combustion Network (ECN)

Diffuse back-illumination setup for high temporally resolved extinction imaging

Development of long range, real-time, and high resolution 3D imaging ladar

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