Mr. Janos C. Keresztes Profile

Janos C. Keresztes

senior optical system engineer at CY Vision

SPIE Involvement:

Author

Area of Expertise:

spectral illumination design , computer vision , Hyperspectral imaging , image analysis , mechanical damage modeling

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Company Website

Publications (5)

Proceedings Article | 17 October 2016 Paper

An automated imaging BRDF polarimeter for fruit quality inspection

Jacob Boyer, Janos Keresztes, Wouter Saeys, John Koshel

Proceedings Volume 9948, 99481G (2016) https://doi.org/10.1117/12.2239008

KEYWORDS: Bidirectional reflectance transmission function, Polarimetry, Inspection, Polarization, Machine vision, Imaging systems, Linear polarizers, Polarizers, Data acquisition, Calibration

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Proceedings Article | 28 September 2015 Paper

A cross-polarized freeform illumination design for glare reduction in fruit quality inspection

Janos Keresztes, R. John Koshel, Russel Chipman, John Stover, Wouter Saeys

Proceedings Volume 9629, 962904 (2015) https://doi.org/10.1117/12.2193858

KEYWORDS: Bidirectional reflectance transmission function, Polarization, Imaging systems, Short wave infrared radiation, Lens design, Tolerancing, Inspection, Light, Hyperspectral imaging, Domes

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Common illumination systems in short wave infrared (SWIR) hyperspectral imaging (HSI) include direct or indirect tungsten halogen lights. While direct lights provide more radiation onto the samples than dome setups, thus being more energy efficient, the acquired images often suffer from specular reflections and gloss. Glare artifacts in images increase variability in the data limiting the accuracy of machine vision algorithms for defect detection and quality inspection, or even providing false positives. Although domes are known to provide a near Lambertian illumination and glare free images, glossy regions and heterogeneities may remain in the data in practice. More particularly, in the field of fruit and vegetable quality inspection, due to their waxy surface, it remains challenging to design an efficient realistic lighting system. This paper suggests a new approach to optimize the illumination of fruit and vegetables based on measurements of the bidirectional reflectance distribution function (BRDF), shape and Stokes parameters. From these measured values, a BRDF model is loaded into ray-tracing software for realistic illumination engineering in order to determine the most suitable illumination scheme. This concept is applied to apples and a cross polarizer (CP) with freeform optics (FO) optical configuration is proposed, which allows the FO to be optimized to maximize uniformity in the field of view of the imager and removes the parallel polarized gloss on the apples. The performance of this CP illumination system was determined experimentally for a set of apples. This cross polarized (CP) illumination system provided a uniformity (U) of 92% and an efficiency (ν) of 90%, while U = 87% and ν = 14% for an ideal dome configuration when illuminating a rectangular target. The simulated imaged apples with assigned optical properties performed better with CP (U=80%) than when using a dome (U=73%) by 7%. Finally, the sensitivity of the design for the light positioning and spectral tolerance are investigated.

Proceedings Article | 3 September 2015 Paper

Dynamic noise corrected hyperspectral radiometric calibration in the SWIR range using a supercontinuum laser

Janos Keresztes, Ben Aernouts, R. Koshel, Wouter Saeys

Proceedings Volume 9579, 95790A (2015) https://doi.org/10.1117/12.2191101

KEYWORDS: Short wave infrared radiation, Sensors, Calibration, Imaging systems, Monochromators, Optical spheres, Integrating spheres, Diffusers, Cameras, Power meters

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Proceedings Article | 3 September 2015 Paper

Illumination system development using design and analysis of computer experiments

Janos Keresztes, Bart De Ketelaere, Jan Audenaert, R. Koshel, Wouter Saeys

Proceedings Volume 9579, 95790I (2015) https://doi.org/10.1117/12.2191082

KEYWORDS: Computer simulations, Short wave infrared radiation, Stochastic processes, Monte Carlo methods, Lamps, Ray tracing, Halogens, Computing systems, Imaging systems, Process modeling

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Proceedings Article | 2 September 2015 Paper

A high contrast 400-2500 nm hyperspectral checkerboard consisting of Acktar material cut with a femto second laser

Janos Keresztes, Anne Henrottin, Mohammad Goodarzi, Niels Wouters, Jeroen van Roy, Wouter Saeys

Proceedings Volume 9573, 95730Q (2015) https://doi.org/10.1117/12.2191102

KEYWORDS: Short wave infrared radiation, Cameras, Imaging systems, Hyperspectral imaging, Calibration, Machine vision, Laser cutting, Pulsed laser operation, Computer vision technology, MATLAB

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