What is Cosine Correction？
Cosine is a mathematical function used to calculate and specify the characteristics (length & angles) of triangles (Trigonometry). Below right picture is the cosine correction comparison between MK350S Premium and Lambert’s Cosine Law. The ideal value of the red circle was described by Johann Hein¬rich Lambert in 1760 and is called “Lambert’s Cosine Law”. Basically it shows how light intensity changes as the angle of the light changes. MK350S Premium cosine receiver is the blue circle; the optimized cosine and Lambert's cosine law are almost overlapped. It is more in line with international standards for illuminance measurement - JIS AA and DIN B standards and reduced measurement errors effectively.
Cosine Correction and LUX MeasurementCosine correction is associated with measuring illuminance, or how much light brightens a certain area - it is measured in LUX which is lumens per sq. meter. A lumen is a unit of mea-sure that represents an “amount” of visible light. As you can see on the picture below, the yellow area is the total amount of the visible light which is emitted by the bulb; the visible light received in the orange 1 sq. meter area is called LUX.
LUX measurement at Different AnglesNext, you must know that light coming in at an angle will influence the LUX. A light shining from directly above (below left picture LUX: 476 lx) will shine brighter than a light coming in at an oblique angle (below right picture LUX: 449 lx). In fact there is a direct correlation between the angle of the light and amount of brightness - this was explained by Johann Heinrich Lambert in 1760.
UPRtek Spectrometer meets CIE Standard of Cosine Correction for LUX MeterMeasuring light intensity on a flat light meter lens is not so straight forward, especially when trying to measure light coming in at angles and then accurately recording the brightness according to the Lambert’s laws – you need to make adjustments. These adjustments are called Cosine Correction. The UPRtek produced spectrometer conform the cosine correction of the CIE standard for LUX Meter in terms of LUX measurement, that is to say, UPRtek spectrometer meets the characteristics of the LUX Meter. The actual LUX value of the light source (light intensity) come from different angles should be Eθ = E0 Χ cos(θ). E0 is the original LUX value. Below chart is a guide to measuring brightness according to Lambert’s laws.
Cosine Correction for Oblique Angle LightIdeally, Cosine Correction for oblique (angular) light should follow the graph shown above. For example, a light meter received lights coming in at 60 degrees; it should result in about 50% of its original intensity. As the angle becomes less oblique, the intensity should increase according the circular red line in the graph above.
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The CQS（Color Quality Scale）is a new light source quality parameter developed by NIST （National Institute of Standards and Technology）for the new solid-state lighting markets. As we mentioned in the article on what is Color Rendering Index, since CRI proposed by the International Commission on Illumination caused some problems with the use of unsaturated colors and a small amount of sample colors. CQS is using higher saturation color, and proposed 15 new colors to evaluate the light source, the value of 100 represents the best quality of the light source, 0 represents the worst light source quality. Read MoreThe Technical Memorandum, TM-30-15, the new method published by IES in 2015 and has been proposed to the CIE. This new color evaluation function is expected to provide the angle of technological innovation for light source measuring, furthermore, it can help users analyze the color characteristics of the modern and the traditional solid-state light source, and thus enhance the fairness and accuracy of the measurement. Read MoreAn undesired change in visual perception induced by a light stimulus whose luminance or spectral distribution fluctuates with time, for an observer in a certain environment. Read MoreThis article compares three flicker metrics regarding percent flicker, flicker index and SVM. The comparison includes the definition comes from which organization, the definition of itself, calculation formula and the description of the range. If you want to know more about which products have related measurement functions, please click on the relative products tab. Read MoreColor Rendering Index (CRI) is the degree of color perception by the naked human eye under two light sources:light source and sunlight. If the color performance of you artificial light source is close to that of sunlight, the color perceived by the human eye becomes closer to being real which is called " Color Fidelity".UPRtek handheld spectrometer series all provide the color evaluation function -CRI. The UI is intuitive and simple to make your lighting analysis more efficient. It is recommended to lighting manufacturers, academic researchers and lighting designers. For example, if broadcast lighting CRI value is more than 95 grade, we think this light is excellent. Howver, following the technological innovation, people are more strict on color quality requirement and the CRI index still remains the color perception problem. Please refer to the further explanation below: Read MoreIt depends on users’application needs. Users can adjust the distance of measuring based on their requirements. For example, when a designer sets up the internal lighting and finds out that the light intensity is insufficient in a specific area, the general practices are to increase the numbers of the lights or adjust the installation of height from above to below to make the best display of the whole area. In the same way, you can fix it reversely when lights emit too much intensities. Therefore, users can quantify the light source, get the illuminance value (Lux) with MK350 series handheld spectrometers as well as adjust the numbers and height of the fixtures based on their needs on the current lighting demands. MK350 handheld spectrometers are the best helper to detect the light quality and intensity changes which improve the lighting visual experiences and meet the requirements of the energy saving needs. Read More
- Academic and Iindustrial Applications
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- Spectrometer Application
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- How to get the latest version firmware on my UPRtek spectrometer?
- How to use UPRtek handheld spectrometer for light measurement?
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- What does the abbreviation mean which is used on UPRtek spectrometer?
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- How to download the uSpectrum PC Software?
- How to download the uFlicker PC Software?
- Is my handheld spectrometer compatible with uSpectrum PC software?
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- Where can I find the saved spectrum / CIE images through uSpectrum APPs on smart device after using uSpectrum APPs and save the data?
- What is LED CRI (Color Rendering Index)?
- What is CQS (Color Quality Scale)?
- What is IES TM-30-15?
- What is TLA (Temporal Light Artifacts) ?
- What is Flicker Metrics (Percent Flicker, Flicker Index, SVM) ?
- What is Cosine Correction？
- What is the recommended measuring distance using UPRtek handheld spectrometer?
- Product Q&A
UPRtek What is Cosine Correction？ Introduction
United Power Research Technology Corp. is Taiwan supplier and manufacturer in Optoelectronics Industry. UPRtek has been offering our customers high quality Spectrometer, Color Meter, Spectral PAR Meter, Spectral Color Meter, Spectrum, LED Meter, Spectradiometer, LED Measurement, LED light testing since 2010. With both advanced technology and 10 years experience, UPRtek always make sure to meet each customer's demand.