Improving Optical Measurements: Non-Linearity Compensation of Compact Charge-Coupled Device (CCD) Spectrometers

Charge-coupled device (CCD) spectrometers are widely used as detectors in analytical laboratory instruments and as sensors for in situ optical measurements. However, as the applications become more complex, the physical and electronic limits of the CCD spectrometers may restrict their applicability. The errors due to dark currents, temperature variations, and blooming can be readily corrected. However, a correction for uncertainty of integration time and wavelength calibration is typically lacking in most devices, and detector non-linearity may distort the signal by up to 5% for some measurements. Here, we propose a simple correction method to compensate for non-linearity errors in optical measurements where compact CCD spectrometers are used. The results indicate that the error due to the non-linearity of a spectrometer can be reduced from several hundred counts to about 40 counts if the proposed correction function is applied.

Download Full-text

Assessing an Atmospheric Correction Algorithm for Time Series of Satellite-Based Water-Leaving Reflectance Using Match-Up Sites in Australian Coastal Waters

Remote Sensing ◽

10.3390/rs13101927 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1927

Author(s):

Fuqin Li ◽

David Jupp ◽

Thomas Schroeder ◽

Stephen Sagar ◽

Joshua Sixsmith ◽

...

Keyword(s):

Coastal Waters ◽

Atmospheric Correction ◽

Correction Method ◽

In Situ Measurements ◽

Landsat 8 ◽

Correction Algorithm ◽

Simple Method ◽

North East ◽

The Impact

An atmospheric correction algorithm for medium-resolution satellite data over general water surfaces (open/coastal, estuarine and inland waters) has been assessed in Australian coastal waters. In situ measurements at four match-up sites were used with 21 Landsat 8 images acquired between 2014 and 2017. Three aerosol sources (AERONET, MODIS ocean aerosol and climatology) were used to test the impact of the selection of aerosol optical depth (AOD) and Ångström coefficient on the retrieved accuracy. The initial results showed that the satellite-derived water-leaving reflectance can have good agreement with the in situ measurements, provided that the sun glint is handled effectively. Although the AERONET aerosol data performed best, the contemporary satellite-derived aerosol information from MODIS or an aerosol climatology could also be as effective, and should be assessed with further in situ measurements. Two sun glint correction strategies were assessed for their ability to remove the glint bias. The most successful one used the average of two shortwave infrared (SWIR) bands to represent sun glint and subtracted it from each band. Using this sun glint correction method, the mean all-band error of the retrieved water-leaving reflectance at the Lucinda Jetty Coastal Observatory (LJCO) in north east Australia was close to 4% and unbiased over 14 acquisitions. A persistent bias in the other strategy was likely due to the sky radiance being non-uniform for the selected images. In regard to future options for an operational sun glint correction, the simple method may be sufficient for clear skies until a physically based method has been established.

Download Full-text

An Adaptive Response Surface Method Using Bayesian Metric and Model Bias Correction Function

Journal of Mechanical Design ◽

10.1115/1.4026095 ◽

2014 ◽

Vol 136 (3) ◽

Cited By ~ 3

Author(s):

Lei Shi ◽

Ren-Jye Yang ◽

Ping Zhu

Keyword(s):

Response Surface ◽

Bias Correction ◽

Adaptive Response ◽

Large Scale ◽

Correction Method ◽

Data Uncertainty ◽

Correction Function ◽

Surface Model ◽

Model Bias ◽

Adaptive Response Surface Method

The Bayesian metric was used to select the best available response surface in the literature. One of the major drawbacks of this method is the lack of a rigorous method to quantify data uncertainty, which is required as an input. In addition, the accuracy of any response surface is inherently unpredictable. This paper employs the Gaussian process based model bias correction method to quantify the data uncertainty and subsequently improve the accuracy of a response surface model. An adaptive response surface updating algorithm is then proposed for a large-scale problem to select the best response surface. The proposed methodology is demonstrated by a mathematical example and then applied to a vehicle design problem.

Download Full-text

Oceanographic lidar profiles compared with estimates from in situ optical measurements

Applied Optics ◽

10.1364/ao.52.000786 ◽

2013 ◽

Vol 52 (4) ◽

pp. 786 ◽

Cited By ~ 29

Author(s):

Jennifer H. Lee ◽

James H. Churnside ◽

Richard D. Marchbanks ◽

Percy L. Donaghay ◽

James M. Sullivan

Keyword(s):

Optical Measurements

Download Full-text

In- Situ Optical measurements of sediment type and phytobenthos of tidal flats: A basis for imaging remote sensing spectroscopy

Deutsche Hydrographische Zeitschrift ◽

10.1007/bf02764045 ◽

1997 ◽

Vol 49 (2-3) ◽

pp. 367-373 ◽

Cited By ~ 4

Author(s):

Hans Hakvoort ◽

Kerstin Heymann ◽

Christian Stein ◽

Desmond Murphy

Keyword(s):

Remote Sensing ◽

Tidal Flats ◽

Optical Measurements ◽

Sediment Type

Download Full-text

In situ optical measurements of bacterial endospore breakdown in a shock tube

Applied Physics B ◽

10.1007/s00340-011-4844-1 ◽

2012 ◽

Vol 106 (3) ◽

pp. 769-774 ◽

Cited By ~ 3

Author(s):

A. D. McCartt ◽

S. Gates ◽

P. Lappas ◽

J. B. Jeffries ◽

R. K. Hanson

Keyword(s):

Shock Tube ◽

Optical Measurements

Download Full-text

Sensitive In Situ Monitoring of a Recombinant Bioluminescent Yersinia enterocolitica Reporter Mutant in Real Time on Camembert Cheese

Applied and Environmental Microbiology ◽

10.1128/aem.68.11.5737-5740.2002 ◽

2002 ◽

Vol 68 (11) ◽

pp. 5737-5740 ◽

Cited By ~ 20

Author(s):

Ariel Maoz ◽

Ralf Mayr ◽

Geraldine Bresolin ◽

Klaus Neuhaus ◽

Kevin P. Francis ◽

...

Keyword(s):

Real Time ◽

Yersinia Enterocolitica ◽

Photon Emission ◽

Photon Counting ◽

In Situ Monitoring ◽

Charge Coupled Device ◽

Reading Frame ◽

Intensified Charge Coupled Device ◽

Camembert Cheese

ABSTRACT Bioluminescent mutants of Yersinia enterocolitica were generated by transposon mutagenesis using a promoterless, complete lux operon (luxCDABE) derived from Photorhabdus luminescens, and their production of light in the cheese environment was monitored. Mutant B94, which had the lux cassette inserted into an open reading frame of unknown function was used for direct monitoring of Y. enterocolitica cells on cheeses stored at 10°C by quantifying bioluminescence using a photon-counting, intensified charge-coupled device camera. The detection limit on cheese was 200 CFU/cm2. Bioluminescence of the reporter mutant was significantly regulated by its environment (NaCl, temperature, and cheese), as well as by growth phase, via the promoter the lux operon had acquired upon transposition. At low temperatures, mutant B94 did not exhibit the often-reported decrease of photon emission in older cells. It was not necessary to include either antibiotics or aldehyde in the food matrix in order to gain quantitative, reproducible bioluminescence data. As far as we know, this is the first time a pathogen has been monitored in situ, in real time, in a “real-product” status, and at a low temperature.

Download Full-text

Ultra-Widefield Fluorescein Angiography Image Brightness Compensation Based on Geometrical Features

Sensors ◽

10.3390/s22010012 ◽

2021 ◽

Vol 22 (1) ◽

pp. 12

Author(s):

Wojciech Więcławek ◽

Marta Danch-Wierzchowska ◽

Marcin Rudzki ◽

Bogumiła Sędziak-Marcinek ◽

Slawomir Jan Teper

Keyword(s):

Image Quality ◽

Fluorescein Angiography ◽

Imaging Modality ◽

Correction Method ◽

Correction Function ◽

Image Brightness ◽

Geometrical Features ◽

Noticeable Improvement ◽

Manual Processing ◽

Image Quality Measures

Ultra-widefield fluorescein angiography (UWFA) is an emerging imaging modality used to characterise pathologies in the retinal vasculature, such as microaneurysms (MAs) and vascular leakages. Despite its potential value for diagnosis and disease screening, objective quantitative assessment of retinal pathologies by UWFA is currently limited because laborious manual processing is required. In this report, we describe a geometrical method for uneven brightness compensation inherent to UWFA imaging technique. The correction function is based on the geometrical eyeball shape, therefore it is fully automated and depends only on pixel distance from the center of the imaged retina. The method’s performance was assessed on a database containing 256 UWFA images with the use of several image quality measures that show the correction method improves image quality. The method is also compared to the commonly used CLAHE approach and was also employed in a pilot study for vascular segmentation, giving a noticeable improvement in segmentation results. Therefore, the method can be used as an image preprocessing step in retinal UWFA image analysis.

Download Full-text