Chul-Woung Park

A novel linearity tester for optical detectors using high-brightness light emitting diodes

We present a linearity tester for optical detectors, which is based on the flux-addition method using two high-brightness light emitting diodes (LEDs) as the light source. The tester is operated with a novel data-acquisition algorithm that determines the switching and data-reading sequence for eliminating the measurement error caused by a drift of the LED radiant flux. Linearity measurement with an uncertainty of as low as 10−4 in a dynamic range over six decades is experimentally demonstrated with simple setup, short measurement time and fully automated operation.

Simultaneous measurement of emittance, transmittance, and reflectance of semitransparent materials at elevated temperature

A two-substrate method is developed to simultaneously determine emissivity, transmittance, and reflectance of semitransparent materials with a single measurement under the same environment at elevated temperature. The three quantities can be obtained through the emissivities of substrates and the apparent emissivities resulting from the radiance of the sample heated by substrates. The two-substrate method is compared with the conventional method by measuring sapphire samples with various thicknesses, resulting in good agreements for all the samples. The present method will be useful to measure the temperature dependence of optical properties of porous ceramic materials.

Final report on bilateral comparison APMP.PR-K1.a.1-2008 between KRISS (Korea) and VNIIOFI (Russia): Spectral irradiance from 250 nm to 2500 nm

Korea Research Institute of Standards and Science (KRISS) and All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI) conducted a bilateral comparison on spectral irradiance over the spectral region from 250 nm to 2500 nm in 2008. The aim of this comparison was to assess the equivalence of the spectral irradiance scales between the two laboratories and to link the KRISS spectral irradiance scale to the results of key comparison CCPR-K1.a carried out in the years 2000–2003. The technical protocol was approved by the CCPR Working Group on Key Comparisons in April 2008. KRISS acted as the pilot to reduce the workload of VNIIOFI as the link laboratory. PTB acted as the neutral partner to ensure blindness of the comparison results. PTB collected the measurement results from and sent them back to both participants. KRISS prepared this report based on the measurement results distributed by PTB. The spectral irradiances measured by KRISS and VNIIOFI agreed within the standard uncertainties (k = 1) from 250 nm to 2500 nm. The unilateral degrees of equivalence of KRISS were calculated using the unilateral degrees of equivalence of VNIIOFI to link the KRISS spectral irradiance scale to the key comparison CCPR-K1.a. The uncertainties of the unilateral degrees of equivalence of KRISS were determined using the uncertainties of KRISS and VNIIOFI measurements and the uncertainties of the unilateral degrees of equivalence of VNIIOFI, and taking into account the correlation of VNIIOFI measurements between the CCPR key and this bilateral comparison. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Size-of-source Effect and Self-radiation Effect of an Infrared Radiation Thermometer

All radiation thermometers have a size-of-source effect (SSE) and a self-radiation effect (SRE). The SSE,defined as dependence of the detector signal of a radiation thermometer on the diameter of a source, is critically dependent on the wavelength since diffraction is the main cause. In this paper, we have measured the SSE and the SRE of TRT2 (Transfer Radiation Thermometer 2, HEITRONICS) widely used as a transfer standard in low and middle temperature range. At , The radiation temperature difference between the 60 mm diameter blackbody and 10 mm diameter blackbody due to the SSE was estimated to be in low temperature mode () and in middle temperature mode (). In addition, the measured radiation temperature difference of the blackbody due to the SRE was found to be 110 mK when the body temperature change of TRT2 was set at .

End-gas temperature measurements in a DOHC spark-ignition engine using CARS

We adopted a broadband CARS technique to measure end-gas temperatures in a combustion chamber of a conventional 4-cylinder DOHC spark-ignition engine. A mobile CARS system measured a full CARS spectrum on a shot by shot basis. The system consisted of a frequency doubled Nd:YAG laser (Continuum Surlite II), broadband modeless dye laser and a monochromator equipped with an optical multi-channel analyzer (RG&G 1420).

Construction and Measurement of Normal Spectral Emissivity Device using Fourier Transform Infrared Spectrometer

An Instrument to measure normal spectral emissivity is built using a Fourier Transform-Infrared (FT-IR) spectrometer. The instrument is composed of four main parts, reference blackbody, sample furnace, optics system, and FT-IR spectrometer. Measurement ranges of temperature and wavelength are and , respectively. Measured emissivity of the reference blackbody is greater than 0.9993 with combined relative uncertainty less than 0.69%, which can be considered an ideal blackbody. We studied the emissivity of opaque alumina, graphite, anodized aluminum, and steel (IMS 200). It is shown that emissivity increases with the roughness of the steel (IMS 200) surface.

Consistency of the Temperature Scales above the Silver Freezing Point Realized at Four Different Spectral Bands

Above the freezing point of silver, the definition of the ITS-90 allows us to select the spectral band and the bandwidth of the radiance comparator and to choose a reference radiance blackbody from the silver, gold, and copper freezing points. We realized the ITS-90 in reference to a copper point blackbody using a radiation thermometer with four different spectral bands. The spectral characteristics of the thermometer were separately measured at each band using a spectral responsivity comparator with a silicon photodiode as a reference detector. To confirm the consistency of the scales we measured the temperature of a silver point blackbody and compared the value with that defined by the ITS-90. We also compared the scales realized at the different bands using a variable temperature blackbody from 800rfloorC to 2500rfloorC. The measured temperature of the silver point agrees with the definition within 10 mK and the realized scales agree with each other within the uncertainty of the scales

Accuracy improvement in the source-based calibration of radiative heat flux sensors by consideration of the temperature non-uniformity of the high temperature blackbody

We have improved the accuracy in source-based calibration of radiative heat flux sensors by considering the temperature non-uniformity of the blackbody cavity. The method measures the responsivity of a heat flux sensor as a function of distance from the blackbody aperture. From this variation of the responsivity, the temperature distribution and the effective emissivity of the blackbody can be determined via a Monte Carlo simulation. The calibration uncertainty is evaluated to be 2.3% (k = 2) for irradiance values up to 10 kW m−2 at a blackbody temperature around 2900 °C. In order to verify the accuracy improvement, the results are compared with those of a detector-based calibration, which demonstrated an agreement within the uncertainty.