Farshid Manoocheri | Aalto University (original) (raw)

Papers by Farshid Manoocheri

Metrologia, 2003

The importance of reliable spectral transmittance measurements for reliable thin-film characteriz... more The importance of reliable spectral transmittance measurements for reliable thin-film characterization is demonstrated. By using a model of the spectral transmittance of thin-film samples, the effect of various uncertainty components in transmittance measurements on the determined thin-film parameters is analysed. The experimental results for aluminium dioxide and tantalum pentoxide thin-film samples show good agreement with the model.

Metrologia, 2008

ABSTRACT Methods for reducing reflectance losses at multiple wavelengths with a silicon photodiod... more ABSTRACT Methods for reducing reflectance losses at multiple wavelengths with a silicon photodiode detector are described. Using thick oxide layer and Brewster-angle operation it is shown that specular reflectance losses can be theoretically decreased below 1 ppm (part per million) in a simple measurement arrangement. Additionally, a detector structure is presented which can be used to reduce the measurement uncertainties due to diffuse reflectance below 1 ppm, even if the total diffuse reflectance losses from a plain photodiode would be two orders of magnitude larger.

Journal of Geophysical Research, 2000

A method developed at the Helsinki University. of Technology (HUT) for calibrating standard lamps... more A method developed at the Helsinki University. of Technology (HUT) for calibrating standard lamps of spectral irradiance in UV-A and UV-B regions is presented. The method is based on a compact filter radiometer that is characterized absolutely to measure spectral irradiance. The filter radiometer can be brought to laboratories where accurate calibrations are needed. The method overcomes some of the instability. problems encountered when using lamps as transfer standards, which makes it also useful in intercomparison campaigns. Test measurements are presented where two standard lamps issued by the National Institute of Standards and Technology (NIST), USA, are compared with the HUT scale held by the radiometer. The results suggest that the agreement between the two scales (HUT and NIST) is approximately 1% -2% in the wavelength region from 300 nm to 400 nm.

Applied Optics, 2008

A goniofluorometer has been built that is capable of measuring in various viewing angles ranging ... more A goniofluorometer has been built that is capable of measuring in various viewing angles ranging from 10°to 90°. The incident angle can be varied from 0°to 8°. The goniofluorometer can measure bispectral luminescent radiance factors in the wavelength range of 250-800 nm. To our knowledge, there are no other reported results of similar devices capable of spectral measurements in various measurement geometries.

A comparison of the scales of spectral diffuse reflectance of the Helsinki University of Technolo... more A comparison of the scales of spectral diffuse reflectance of the Helsinki University of Technology (TKK) and the Singapore National Metrology Centre (SPRING) was made. A PTFE-type reflectance standard with a nominal reflectance of 98% was measured for the 8/d reflectance factors over the wavelength range from 360 to 780 nm. A good agreement was found between the results of TKK and SPRING. Most of the measured values of spectral diffuse reflectance agreed within 0.36 %, the relative standard uncertainty of the comparison (1 level).

Oblique-incidence spectrophotometric measurements are considered for reliable determination of th... more Oblique-incidence spectrophotometric measurements are considered for reliable determination of the refractive index and thickness of thin-film coatings. By using a model of the spectral transmittance of thin film samples, the effect of systematic factors on the determined thin-film parameters is analyzed. The optical parameters of a silicon-dioxide sample determined from the experimental results obtained with the HUT spectrophotometer are consistent for the incidence angles between 0 and 56.4 degrees, demonstrating high accuracy of film-parameter determination.

Measurement Science & Technology, 2006

We have developed and characterized new detectors based on germanium (Ge) photodiodes to be used ... more We have developed and characterized new detectors based on germanium (Ge) photodiodes to be used in the wavelength region between 900 and 1650 nm. The effects of spatial uniformity, temperature and low shunt resistance on the spectral responsivity measurements are studied. Our results for the spatial uniformities show improvements as compared with earlier studies. The spectral reflectances of a Ge photodiode and trap detector are also studied, and the trap reflectance is found to be less than 10 −4 at wavelengths longer than 900 nm. The results of this study show that with careful use, the large area Ge photodiodes can offer a cost-effective alternative as compared with InGaAs photodiodes of similar diameters.

Metrologia, 2009

Calculations of reflectance required for designing a predictable quantum efficient detector (PQED... more Calculations of reflectance required for designing a predictable quantum efficient detector (PQED) are presented. The PQED will be based on natural inversion layer photodiodes and it is expected to measure optical power with an uncertainty of 1 ppm. To achieve such a low level of uncertainty, the associated reflectance of the PQED must be of the same order of magnitude. The wavelength range from 450 nm to 900 nm and the oxide layer thickness from 10 nm to 500 nm were used in the calculations of specular reflectance. The results show that a simple two-photodiode design is suitable for the PQED if scattering from the surface of the photodiode is less than 1 ppm. For higher scattering up to 100 ppm, a more advanced detector structure may allow control of this uncertainty component at the level of 1 ppm.

Metrologia, 2000

A method of measuring the absolute spectral irradiance of quartz-halogen-tungsten lamps is descri... more A method of measuring the absolute spectral irradiance of quartz-halogen-tungsten lamps is described, based on the known responsivity of a filter radiometer, the components of which are separately characterized. The characterization is described for the wide wavelength range essential for deriving the spectrum of a lamp, from 260 nm to 950 nm. Novel methods of interpolation and measurement are implemented for the spectral responsivity of the filter radiometer. The combined standard uncertainty of spectral irradiance measurements is less than 1.4 parts in 102 from 290 nm to 320 nm (ultraviolet B) and 4 parts in 103 from 440 nm to 900 nm (visible to near-infrared). As an example, the derived spectral irradiances of two lamps measured at the Helsinki University of Technology (HUT, Finland) are presented and compared with the measurement results of the National Institute of Standards and Technology (NIST, USA) and the Physikalisch-Technische Bundesanstalt (PTB, Germany). The comparisons indicate that the HUT spectral irradiance scale is between those of the NIST and the PTB in the wavelength range 290 nm to 900 nm. The long-term reproducibility of the spectral irradiance measurements is also presented. Over a period of two years, the reproducibility appears to be better than 1 part in 102.

The potential discrepancies between the gonioreflectometer based and integrating-sphere based met... more The potential discrepancies between the gonioreflectometer based and integrating-sphere based methods in the measurement of spectral diffuse reflectance are studied. Errors due to scattered light around the measurement beam in gonioreflectometers are a potential cause of such discrepancies. Procedures used to determine such errors and the required corrections are presented. At TKK, the corrections varied from -1,1% to -0,2% for the studied two cases. The measurement results for our diffuse reflectance reference materials with the appropriate corrections in both cases are in excellent agreement.

Applied Optics, 2009

. Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflec... more . Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflectance. Applied Optics, volume 48, number 15, pages 2947Optics, volume 48, number 15, pages -2957 A comparison between the absolute gonioreflectometric scales at the Helsinki University of Technology (TKK) and the Physikalisch-Technische Bundesanstalt (PTB) has been accomplished. Six different reflection standards were measured for their 0∶45 spectral radiance factor between 250 and 1650 nm in 10 nm intervals. Also, the 0∶d reflectance factor between 400 and 1600 nm in 100 nm intervals was determined from goniometric reflectance measurements over polar angles with subsequent integration within the hemisphere above the sample. Goniometric comparisons covering such an extensive wavelength range and also several different sample materials are rarely implemented. For all but one sample, the difference between the results obtained at the TKK and the PTB was, with the exception of a couple of measurement points, within the expanded uncertainty (k ¼ 2) of the comparison at least up to a wavelength of 1400 nm. All differences between the measurement results can be understood, except for one translucent sample in the visible wavelength range. The effect of sample translucency was found to be significant in the NIR wavelength region. Also, a general tendency of an increase of the TKK values relative to the PTB values in the UV region was observed. Possible causes for this phenomenon are discussed.

Metrologia, 2007

Silja Holopainen, Farshid Manoocheri, Saulius Nevas, and Erkki Ikonen. 2007. Effect of light scat... more Silja Holopainen, Farshid Manoocheri, Saulius Nevas, and Erkki Ikonen. 2007. Effect of light scattering from source optics in goniometric diffuse reflectance measurements. Metrologia, volume 44, number 3, pages 167-170.

Applied Optics, 2004

Gonioreflectometric determination of reflectance factors that involves hemispherical collection o... more Gonioreflectometric determination of reflectance factors that involves hemispherical collection of reflected flux, which is an alternative to integrating sphere-based methods, is discussed. A detailed description of a gonioreflectometer built at the Helsinki University of Technology is presented. The instrument is used to establish an absolute scale of total diffuse reflectance factors throughout the spectral range 360 -830 nm. The hemispherical reflectance factors are obtained through integration of the gonioreflectometric measurement results. The reflectance factors of white high-quality artifacts can be determined with a combined standard uncertainty of 0.20%. Results of test measurements were found to be in agreement with values traceable to other absolute scales based on integrating-sphere methods.

Applied Optics, 2006

The optical parameters of a SiO 2 thin-film coating determined from the spectral reflectance and ... more The optical parameters of a SiO 2 thin-film coating determined from the spectral reflectance and transmittance measurements at various incidence angles, including the normal incidence and the Brewster's angle, are compared in this paper. The high-accuracy measurements were carried out through visiblenear-infrared spectral regions by using our purpose-built instruments. The optical parameters obtained from the reflectance and the transmittance data are consistent over the angles of incidence and agree within 0.2%. The effect of important systematic factors in the oblique-incidence spectrophotometric measurements is also discussed.

Metrologia, 2012

The spectral responsivity of a predictable quantum efficient detector (PQED) is calculated based ... more The spectral responsivity of a predictable quantum efficient detector (PQED) is calculated based on the responsivity of an ideal quantum detector and taking into account reflection losses from the surface of the photodiode and internal charge-carrier gains/losses inside the diode. The internal quantum deficiency (IQD) is obtained from simulations with the PC1D software using the material data of the produced PQED photodiodes. The results indicate that at room temperature the predicted IQD of the PQED is close to zero with an uncertainty of about 100 ppm over the visible range. It is further concluded that a primary standard of visible optical power with an uncertainty of approximately 1 ppm is achievable using the PQED at low temperatures.

Metrologia, 2009

The commonly made assumption of Lambertian behaviour of fluorescence emission has been studied in... more The commonly made assumption of Lambertian behaviour of fluorescence emission has been studied in solid amorphous material. A goniofluorometer capable of measurements in measurement geometries from 0 : 10 to 0 : 85 has been used for this purpose. The measurements indicate that the fluorescence emission from solid amorphous material is clearly non-Lambertian.

Metrologia, 2003

Results of filter radiometer characterization with a wavelength-tunable Ti : sapphire laser in th... more Results of filter radiometer characterization with a wavelength-tunable Ti : sapphire laser in the wavelength band around 900 nm are presented. The effect of interference between the reflections from filter surfaces in the case of coherent laser light was studied and reduced with a special filter design with antireflection coatings. Measuring the responsivity as a function of wavelength over a very narrow band was used to reveal the remaining interference effects. Uncertainty analysis and test results indicate that filter radiometers can be characterized with a relative standard uncertainty of 9×10−4 using the scanning method. The results agree well with more conventional monochromator-based measurements.

Applied Optics, 2009

. Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflec... more . Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflectance. Applied Optics, volume 48, number 15, pages 2947Optics, volume 48, number 15, pages -2957 A comparison between the absolute gonioreflectometric scales at the Helsinki University of Technology (TKK) and the Physikalisch-Technische Bundesanstalt (PTB) has been accomplished. Six different reflection standards were measured for their 0∶45 spectral radiance factor between 250 and 1650 nm in 10 nm intervals. Also, the 0∶d reflectance factor between 400 and 1600 nm in 100 nm intervals was determined from goniometric reflectance measurements over polar angles with subsequent integration within the hemisphere above the sample. Goniometric comparisons covering such an extensive wavelength range and also several different sample materials are rarely implemented. For all but one sample, the difference between the results obtained at the TKK and the PTB was, with the exception of a couple of measurement points, within the expanded uncertainty (k ¼ 2) of the comparison at least up to a wavelength of 1400 nm. All differences between the measurement results can be understood, except for one translucent sample in the visible wavelength range. The effect of sample translucency was found to be significant in the NIR wavelength region. Also, a general tendency of an increase of the TKK values relative to the PTB values in the UV region was observed. Possible causes for this phenomenon are discussed.

Metrologia, 2009

The applicability of biased and random error models for determining the uncertainty of photometer... more The applicability of biased and random error models for determining the uncertainty of photometer quality factor f_1' using Monte Carlo simulations is investigated. In the biased error model the contribution to the measured value has the same sign and almost the same magnitude at neighbouring wavelengths, whereas in the random error model contributions of varying signs appear at the neighbouring

Metrologia, 2003

The importance of reliable spectral transmittance measurements for reliable thin-film characteriz... more The importance of reliable spectral transmittance measurements for reliable thin-film characterization is demonstrated. By using a model of the spectral transmittance of thin-film samples, the effect of various uncertainty components in transmittance measurements on the determined thin-film parameters is analysed. The experimental results for aluminium dioxide and tantalum pentoxide thin-film samples show good agreement with the model.

Metrologia, 2008

ABSTRACT Methods for reducing reflectance losses at multiple wavelengths with a silicon photodiod... more ABSTRACT Methods for reducing reflectance losses at multiple wavelengths with a silicon photodiode detector are described. Using thick oxide layer and Brewster-angle operation it is shown that specular reflectance losses can be theoretically decreased below 1 ppm (part per million) in a simple measurement arrangement. Additionally, a detector structure is presented which can be used to reduce the measurement uncertainties due to diffuse reflectance below 1 ppm, even if the total diffuse reflectance losses from a plain photodiode would be two orders of magnitude larger.

Journal of Geophysical Research, 2000

A method developed at the Helsinki University. of Technology (HUT) for calibrating standard lamps... more A method developed at the Helsinki University. of Technology (HUT) for calibrating standard lamps of spectral irradiance in UV-A and UV-B regions is presented. The method is based on a compact filter radiometer that is characterized absolutely to measure spectral irradiance. The filter radiometer can be brought to laboratories where accurate calibrations are needed. The method overcomes some of the instability. problems encountered when using lamps as transfer standards, which makes it also useful in intercomparison campaigns. Test measurements are presented where two standard lamps issued by the National Institute of Standards and Technology (NIST), USA, are compared with the HUT scale held by the radiometer. The results suggest that the agreement between the two scales (HUT and NIST) is approximately 1% -2% in the wavelength region from 300 nm to 400 nm.

Applied Optics, 2008

A goniofluorometer has been built that is capable of measuring in various viewing angles ranging ... more A goniofluorometer has been built that is capable of measuring in various viewing angles ranging from 10°to 90°. The incident angle can be varied from 0°to 8°. The goniofluorometer can measure bispectral luminescent radiance factors in the wavelength range of 250-800 nm. To our knowledge, there are no other reported results of similar devices capable of spectral measurements in various measurement geometries.

A comparison of the scales of spectral diffuse reflectance of the Helsinki University of Technolo... more A comparison of the scales of spectral diffuse reflectance of the Helsinki University of Technology (TKK) and the Singapore National Metrology Centre (SPRING) was made. A PTFE-type reflectance standard with a nominal reflectance of 98% was measured for the 8/d reflectance factors over the wavelength range from 360 to 780 nm. A good agreement was found between the results of TKK and SPRING. Most of the measured values of spectral diffuse reflectance agreed within 0.36 %, the relative standard uncertainty of the comparison (1 level).

Oblique-incidence spectrophotometric measurements are considered for reliable determination of th... more Oblique-incidence spectrophotometric measurements are considered for reliable determination of the refractive index and thickness of thin-film coatings. By using a model of the spectral transmittance of thin film samples, the effect of systematic factors on the determined thin-film parameters is analyzed. The optical parameters of a silicon-dioxide sample determined from the experimental results obtained with the HUT spectrophotometer are consistent for the incidence angles between 0 and 56.4 degrees, demonstrating high accuracy of film-parameter determination.

Measurement Science & Technology, 2006

We have developed and characterized new detectors based on germanium (Ge) photodiodes to be used ... more We have developed and characterized new detectors based on germanium (Ge) photodiodes to be used in the wavelength region between 900 and 1650 nm. The effects of spatial uniformity, temperature and low shunt resistance on the spectral responsivity measurements are studied. Our results for the spatial uniformities show improvements as compared with earlier studies. The spectral reflectances of a Ge photodiode and trap detector are also studied, and the trap reflectance is found to be less than 10 −4 at wavelengths longer than 900 nm. The results of this study show that with careful use, the large area Ge photodiodes can offer a cost-effective alternative as compared with InGaAs photodiodes of similar diameters.

Metrologia, 2009

Calculations of reflectance required for designing a predictable quantum efficient detector (PQED... more Calculations of reflectance required for designing a predictable quantum efficient detector (PQED) are presented. The PQED will be based on natural inversion layer photodiodes and it is expected to measure optical power with an uncertainty of 1 ppm. To achieve such a low level of uncertainty, the associated reflectance of the PQED must be of the same order of magnitude. The wavelength range from 450 nm to 900 nm and the oxide layer thickness from 10 nm to 500 nm were used in the calculations of specular reflectance. The results show that a simple two-photodiode design is suitable for the PQED if scattering from the surface of the photodiode is less than 1 ppm. For higher scattering up to 100 ppm, a more advanced detector structure may allow control of this uncertainty component at the level of 1 ppm.

Metrologia, 2000

A method of measuring the absolute spectral irradiance of quartz-halogen-tungsten lamps is descri... more A method of measuring the absolute spectral irradiance of quartz-halogen-tungsten lamps is described, based on the known responsivity of a filter radiometer, the components of which are separately characterized. The characterization is described for the wide wavelength range essential for deriving the spectrum of a lamp, from 260 nm to 950 nm. Novel methods of interpolation and measurement are implemented for the spectral responsivity of the filter radiometer. The combined standard uncertainty of spectral irradiance measurements is less than 1.4 parts in 102 from 290 nm to 320 nm (ultraviolet B) and 4 parts in 103 from 440 nm to 900 nm (visible to near-infrared). As an example, the derived spectral irradiances of two lamps measured at the Helsinki University of Technology (HUT, Finland) are presented and compared with the measurement results of the National Institute of Standards and Technology (NIST, USA) and the Physikalisch-Technische Bundesanstalt (PTB, Germany). The comparisons indicate that the HUT spectral irradiance scale is between those of the NIST and the PTB in the wavelength range 290 nm to 900 nm. The long-term reproducibility of the spectral irradiance measurements is also presented. Over a period of two years, the reproducibility appears to be better than 1 part in 102.

The potential discrepancies between the gonioreflectometer based and integrating-sphere based met... more The potential discrepancies between the gonioreflectometer based and integrating-sphere based methods in the measurement of spectral diffuse reflectance are studied. Errors due to scattered light around the measurement beam in gonioreflectometers are a potential cause of such discrepancies. Procedures used to determine such errors and the required corrections are presented. At TKK, the corrections varied from -1,1% to -0,2% for the studied two cases. The measurement results for our diffuse reflectance reference materials with the appropriate corrections in both cases are in excellent agreement.

Applied Optics, 2009

. Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflec... more . Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflectance. Applied Optics, volume 48, number 15, pages 2947Optics, volume 48, number 15, pages -2957 A comparison between the absolute gonioreflectometric scales at the Helsinki University of Technology (TKK) and the Physikalisch-Technische Bundesanstalt (PTB) has been accomplished. Six different reflection standards were measured for their 0∶45 spectral radiance factor between 250 and 1650 nm in 10 nm intervals. Also, the 0∶d reflectance factor between 400 and 1600 nm in 100 nm intervals was determined from goniometric reflectance measurements over polar angles with subsequent integration within the hemisphere above the sample. Goniometric comparisons covering such an extensive wavelength range and also several different sample materials are rarely implemented. For all but one sample, the difference between the results obtained at the TKK and the PTB was, with the exception of a couple of measurement points, within the expanded uncertainty (k ¼ 2) of the comparison at least up to a wavelength of 1400 nm. All differences between the measurement results can be understood, except for one translucent sample in the visible wavelength range. The effect of sample translucency was found to be significant in the NIR wavelength region. Also, a general tendency of an increase of the TKK values relative to the PTB values in the UV region was observed. Possible causes for this phenomenon are discussed.

Metrologia, 2007

Silja Holopainen, Farshid Manoocheri, Saulius Nevas, and Erkki Ikonen. 2007. Effect of light scat... more Silja Holopainen, Farshid Manoocheri, Saulius Nevas, and Erkki Ikonen. 2007. Effect of light scattering from source optics in goniometric diffuse reflectance measurements. Metrologia, volume 44, number 3, pages 167-170.

Applied Optics, 2004

Gonioreflectometric determination of reflectance factors that involves hemispherical collection o... more Gonioreflectometric determination of reflectance factors that involves hemispherical collection of reflected flux, which is an alternative to integrating sphere-based methods, is discussed. A detailed description of a gonioreflectometer built at the Helsinki University of Technology is presented. The instrument is used to establish an absolute scale of total diffuse reflectance factors throughout the spectral range 360 -830 nm. The hemispherical reflectance factors are obtained through integration of the gonioreflectometric measurement results. The reflectance factors of white high-quality artifacts can be determined with a combined standard uncertainty of 0.20%. Results of test measurements were found to be in agreement with values traceable to other absolute scales based on integrating-sphere methods.

Applied Optics, 2006

The optical parameters of a SiO 2 thin-film coating determined from the spectral reflectance and ... more The optical parameters of a SiO 2 thin-film coating determined from the spectral reflectance and transmittance measurements at various incidence angles, including the normal incidence and the Brewster's angle, are compared in this paper. The high-accuracy measurements were carried out through visiblenear-infrared spectral regions by using our purpose-built instruments. The optical parameters obtained from the reflectance and the transmittance data are consistent over the angles of incidence and agree within 0.2%. The effect of important systematic factors in the oblique-incidence spectrophotometric measurements is also discussed.

Metrologia, 2012

The spectral responsivity of a predictable quantum efficient detector (PQED) is calculated based ... more The spectral responsivity of a predictable quantum efficient detector (PQED) is calculated based on the responsivity of an ideal quantum detector and taking into account reflection losses from the surface of the photodiode and internal charge-carrier gains/losses inside the diode. The internal quantum deficiency (IQD) is obtained from simulations with the PC1D software using the material data of the produced PQED photodiodes. The results indicate that at room temperature the predicted IQD of the PQED is close to zero with an uncertainty of about 100 ppm over the visible range. It is further concluded that a primary standard of visible optical power with an uncertainty of approximately 1 ppm is achievable using the PQED at low temperatures.

Metrologia, 2009

The commonly made assumption of Lambertian behaviour of fluorescence emission has been studied in... more The commonly made assumption of Lambertian behaviour of fluorescence emission has been studied in solid amorphous material. A goniofluorometer capable of measurements in measurement geometries from 0 : 10 to 0 : 85 has been used for this purpose. The measurements indicate that the fluorescence emission from solid amorphous material is clearly non-Lambertian.

Metrologia, 2003

Results of filter radiometer characterization with a wavelength-tunable Ti : sapphire laser in th... more Results of filter radiometer characterization with a wavelength-tunable Ti : sapphire laser in the wavelength band around 900 nm are presented. The effect of interference between the reflections from filter surfaces in the case of coherent laser light was studied and reduced with a special filter design with antireflection coatings. Measuring the responsivity as a function of wavelength over a very narrow band was used to reveal the remaining interference effects. Uncertainty analysis and test results indicate that filter radiometers can be characterized with a relative standard uncertainty of 9×10−4 using the scanning method. The results agree well with more conventional monochromator-based measurements.

Applied Optics, 2009

. Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflec... more . Comparison measurements of 0 : 45 radiance factor and goniometrically determined diffuse reflectance. Applied Optics, volume 48, number 15, pages 2947Optics, volume 48, number 15, pages -2957 A comparison between the absolute gonioreflectometric scales at the Helsinki University of Technology (TKK) and the Physikalisch-Technische Bundesanstalt (PTB) has been accomplished. Six different reflection standards were measured for their 0∶45 spectral radiance factor between 250 and 1650 nm in 10 nm intervals. Also, the 0∶d reflectance factor between 400 and 1600 nm in 100 nm intervals was determined from goniometric reflectance measurements over polar angles with subsequent integration within the hemisphere above the sample. Goniometric comparisons covering such an extensive wavelength range and also several different sample materials are rarely implemented. For all but one sample, the difference between the results obtained at the TKK and the PTB was, with the exception of a couple of measurement points, within the expanded uncertainty (k ¼ 2) of the comparison at least up to a wavelength of 1400 nm. All differences between the measurement results can be understood, except for one translucent sample in the visible wavelength range. The effect of sample translucency was found to be significant in the NIR wavelength region. Also, a general tendency of an increase of the TKK values relative to the PTB values in the UV region was observed. Possible causes for this phenomenon are discussed.

Metrologia, 2009

The applicability of biased and random error models for determining the uncertainty of photometer... more The applicability of biased and random error models for determining the uncertainty of photometer quality factor f_1' using Monte Carlo simulations is investigated. In the biased error model the contribution to the measured value has the same sign and almost the same magnitude at neighbouring wavelengths, whereas in the random error model contributions of varying signs appear at the neighbouring