All posts by caesus

Outlining the Steropes LED Series Light Source

It is impossible to perform accurate transmissive or reflective light measurements without a suitable light source. This was the surprisingly simple principle that underlined the development of Admesy’s halogen and LED light sources. Displays, light emitting diodes (LEDs), and solid-state lighting (SSL) act as their own light sources and spectrophotometric equipment can directly acquire the optical properties without the need for additional illumination. Yet this is not the case for all light measuring applications.

Transmission and reflectivity measurements are only as reliable as the incident light source used to illuminate the sample material. Thin films, foils, glass, and solutions in cuvettes are routinely analyzed through radiometric and colorimetric methods. This enables analysts to assess various physiochemical properties such as the optical density and color of materials in various phases. However, the accuracy of acquired results is utterly dependent on the stability and accuracy of the light source used in light measurement experiments.

This blog post will explore capacities and applications of Admesy’s Steropes LED Series light source in detail.

Steropes LED Series Specifications

The Steropes LED Series is an ultra-stable light source that is internally regulated. It is based around a standard white, a royal blue, or a full-spectrum LED that can adjust its spectral output across its entire range in increments of 0.1%. This translates to outstanding accuracy that is ensured with rapid stabilization within 10 milliseconds.

Custom wavelengths are available for specific spectrometric or colorimetric applications, but the standard Steropes LED Series provides extremely pure and stable lighting across the following ranges:

  • LED natural white: 420 – 780 nanometres (nm);

  • LED royal blue: 410 – 490nm;

  • LED full spectrum: 380 – 780nm;

Each of these is available in stand-alone variations with several interfaces to tightly control the light output in real-time. Regardless of the operating mode, the light source is modulated by a built-in colorimeter which ensures operating accuracy to within 0.1%.

Applications of the Steropes Light Source

The Steropes LED Series light source has a broad range of application areas, with good compatibility for several operating systems thanks to the component’s multiple interfaces. They are also suitable for light measurement experiments in vacuum conditions. This significantly broadens the potential areas of application for the Steropes LED light source. It has successfully been used to measure the transmissivity and reflectivity of solids and is suitable for fluorescence and photoluminescence of chemical samples in cuvettes.

Light Sources from Admesy

Admesy provides an extensive range of light measurement devices for research and development (R&D), quality control (QC), and quality assurance (QA) processes. Our light sources include the Steropes LED Series and the HDX Series of halogen light sources.

If you would like any more information, please do not hesitate to contact us.

Color Measurement: Explaining Color Space and Gamut

The CIE chromaticity diagram maps the average spectral sensitivity of the human eye. This specifies any visible color as a function of three parameters, or tristimulus values, which are analogous to the average sensitivity of human vision to different hues.

This method of color measurement was popularised by the CIE 1931 standard. The color space represented on the CIE 1931 chromaticity diagram shows a distribution of each spectral color around the edge of the space, with all the perceivable hues represented within. This provided a reliable platform for performing accurate color measurements, and it is still broadly used today.

In the context of digital devices, color measurement according to the CIE 1931 standard is often performed to determine the device’s color gamut. This defines the subset of colors that a device can faithfully reproduce.

What is a Colour Gamut?

A color gamut is a measure of the visible wavelength range within a particular color space that a light source can produce. It is typically expressed as an area within the CIE 1931 chromaticity diagram and is subsequently used to determine how much of the visible spectrum can be expressed.

Colour measurement of optical technologies such as 2D digital displays is focused on determining the percentage of a standard color gamut that the device covers. Rec. 709 was the first standardized specification for high-definition visual content, boasting roughly 35.9% coverage of the CIE 1931 color space. This was sufficient when it was first introduced in 1990, but optoelectronic technologies have since outstripped the cathode ray tube (CRT) and standard liquid crystal display (LCD) matrices that were commonplace 28 years ago.

Modern color measurements use several color gamut standards to assess the chromatic performance of a digital device. DCI P3 represents as much as 45.5% of CIE 1931, which is difficult for certain device architectures to achieve. Leading organic light emitting diode (OLED) and UHDTV products on the market are expected to cover up to 100% of DCI P3, but even this has been eclipsed by the onset of Rec. 2020 which is the most complete color space currently envisaged.

Rec. 2020 is a next-generation color gamut that determines the standardized chromatic output of displays of 4K and 8K resolutions. It can be challenging to achieve upwards of 75% Rec. 2020 coverage, with modern color measurements demonstrating the inherent difficulties of reproducing mid-range wavelengths and green spectra.

Colour Measurements with Admesy

Admesy is one of the leading manufacturers of optical devices for color measurements of leading-edge display technologies. We supply an extensive range of spectrometers and colorimeters capable of analyzing the chromatic output of an entire display as well as distinct pigments on the surface. Each of the Hyperion, MSE, Rhea, Hera, and Cronus series measuring instruments is suitable for performing chromatic analysis of display architectures.

If you would like to learn more about our display measurement capabilities, read our previous blog posts:

Or, contact us for any more information about color measurement for achieving maximal coverage of dynamic spectrums.

Reproducibility Challenges for LED Measurement Instruments

The emergence of solid-state lighting (SSL) has rapidly eclipsed the performance and efficiency capacities of incandescent light bulbs. This technology includes LEDs and emerging organic light emitting diodes (OLEDs), which represent exciting potential for future lighting applications. Despite the tantalizing possibilities of OLED technologies, LEDs are still expected to occupy as much as 70% of the lighting market by 2020. This is due to their enhanced spectral performance, energy efficiency, and comparatively low cost of production.

However, LEDs represent unique challenges for light measurement instruments designed for R&D, quality control (QC), and quality assurance (QA) processes. This is due in part to the extremely tight tolerances that arise from such widespread market saturation. LEDs are ubiquitous in modern life, and they must perform accordingly. Various measuring instruments are used to ensure good batch to batch consistency of LED products.

This blog post will explore some of the reproducibility challenges of LED measurement instruments in more detail, with a focus on how optical technologies are overcoming driver-related issues.

Measurement Instruments and Driver Difficulties

An LED is a diode comprised of a dual-lead semiconductor with a junction of positive and negative alloys. It lights up when an electrical current is applied to the junction, causing an electron transference between the two metals and subsequent electroluminescence. The colorimetric properties of an LED are determined by the alloying composition of the p-n junction, as well as the thermal conditions of the diode during operation. As the generation of light also generates low levels of heat, variation in an LED’s spectral output is to be expected.

This is unacceptable in modern consumer environments where stable lighting is essential for a healthy commercial or domestic environment. Digital drivers are routinely used to maintain consistent levels of brightness and suitable RGB levels for stable spectral outputs. However, LED drivers display their own unique challenges for light measurement instruments.

Driver-related variations in LED products include spectral power distribution, radiance, luminance, and even stability. Spectral variations such as flicker are considered an almost unavoidable symptom of alternating current (AC) power supplies, but driver issues can also cause visual fluctuation. Multiple light measurement instruments or a single comprehensive measuring solution must be applied during LED development to assess each of these critical characteristics and remove affected products from market circulation.

Assessing the radiometric, spectroradiometric, and photometric behavior of LEDs using varied light measurement instruments is an assured way of mitigating reproducibility issues inherent in SSL manufacturing. Numerous optical configurations are available from Admesy for 100% inspection of LED products in manufacturing environments.

Measurement Instruments from Admesy

Admesy specializes in precise light measurement instruments for repeatable QA processes in manufacturing environments. We offer the Rhea series spectrometer and the Asteria series light meter to overcome the most common challenges of LED manufacturing. The Rhea series spectrometer can be configured for accurate acquisition of spectral data across the full visible wavelength range (380 – 780nm), with considerations for numerous optical characteristics.

If you would like any more information about the measurement instruments available from Admesy, please do not hesitate to contact us.

[Source: AZOM]

What are Reflection Measurements?

The perception of colour is primarily determined by two objective factors: the wavelengths of light that are reflected from a surface; and the colour of the illuminating light. White light is a combination of lights of different wavelengths in the visible spectrum. A surface will absorb and reflect proportions of these wavelengths dependent upon its colour, for example, vibrant red surfaces will absorb light of shorter wavelengths and reflect wavelengths of >700nm. However, this assumes that the surface is uniform and defect-free.

Specular reflection measurements analyse the light that is rejected from a surface into a singular outgoing direction. The Law of Reflection states that the angle of an incident ray of light is equal to the angle of reflection; provided that the surface is smooth, glossy, and free of defects. Rough or matte materials tend to exhibit diffuse reflection when struck by incident light. This refers to the scattering of wavelengths in multiple directions and is associated with reduced colour saturation and vibrancy.

Reflection measurements are ubiquitously used in product development and quality control (QC) for optical materials and devices such as plastic films, coated glass, and phosphor plates.

This blog post will explore the performance of reflection measurements in more detail.

Reflection Measurements: SCE vs SCI

The colorimetric characteristics of products are routinely assessed to maintain batch-to-batch consistency and support diagnosis of variations in production environments. These reflection measurements can be loosely divided into two subcategories: specular component excluded (SCE); and specular component included (SCI).

Reflection measurements operating on SCE methodology use a reflective probe at 45° to measure a surface’s true colour irrespective of gloss. This uses a stable incident light source such as the Steropes LED, to illuminate the surface and measure reflectance across multiple angles. SCI reflection measurements, meanwhile, use a straight probe at 0° to measure colour and gloss for total measurement of the surface’s appearance.

The latter method requires the integration of the Steropes LED light source to a reflective probe. SCE reflection measurements may also use an M8 optical fibre connection to ensure stability and repeatability for true colour analysis. Admesy supplies both 200 micrometre (μm) and 400 μm reflective probes suitable for interfacing with the Steropes LED light source and our full range of colorimeters.

This setup provides the most accurate form of reflection measurements for R&D and QC purposes.

Reflection Measurements with Admesy

Admesy specialises in the development and supply of ultra-precise optical measuring equipment for industrial and commercial applications. Our reflection measurement instrumentation provides a comprehensive solution for assessing the colorimetric behaviour of specular or diffuse surfaces.

If you would like any more information about our light measurement capabilities, read our previous blog post: What are Transmission Measurements? Or, if you have any questions simply contact us directly.

Color measurement and white point adjustment for automotive R&D

The quality of lighting and displays in the automotive industry are critical design factors. Accurately measuring the colors emitted from the lights and displays enables precise, high-quality results. This article outlines the major solutions for accurate color measurement in vehicle design and manufacturing.

The automotive market is becoming increasingly competitive. Consumers are demanding better, safer, more reliable vehicles that provide a more enjoyable driving experience. As a result, there has been a flurry of technological advances in the automotive industry in recent decades. Automotive design and lighting are no exception to this trend, with a number of significant innovations.

Figure 1: Lighting and displays are an essential aspect of vehicle design. Image credit: pixabay.com/xusenru.

Automotive lighting research enhances efficiency and design

Exterior vehicle lights have advanced rapidly from halogen lamps introduced in the 1970s, to xenon lamps introduced in the 1990s to full LEDs headlamps introduced in 2006.

LED headlamps offer longer lifetimes, increased efficiency, and reduced energy consumption compared to their predecessors. What’s more, adaptive driving beam technologies introduced in 2014 now allow headlights to adapt to every driving situation automatically.

Laser lights represent the latest trend in headlights, offering diodes that are a fraction of the size of LEDs while providing superior efficiency, quality, and performance.1-4

Interior lighting is also becoming an increasingly important part of vehicle design, as studies have shown that ambient interior lighting can improve vehicle attractiveness, perceived safety, and space perception.

LEDs are the main lighting source currently used in interior lighting, but there is continued research into OLEDs, which offer increased design flexibility, and optical fibers, which offer compactness.

While interior lighting is currently focused on providing a superior driver experience, the introduction of autonomous vehicles could completely change how we interact with our vehicles.6,7

Color quality of vehicle lighting and displays is an essential design consideration

Measuring and adjusting optical properties of vehicle components during research and development ensures a high-quality product and increased customer satisfaction. Automotive OEMs and vehicle manufacturers aim to plan their lighting and design schemes precisely to meet consumer and regulatory demands.

Unfortunately, mass production processes can result in small variations in material structure, composition, and thickness that result in spectral variations and color differences in lights and automotive displays.8-10

White point adjustment and color reproduction are an essential part of quality control in automotive research and development. Color measurement can be done using a colorimeter or spectroradiometer.11-13

Measuring color – colorimeter or spectroradiometer?

While both devices offer a ‘correct’ measurement of color, they do so in very different ways. As a result, the context of the measurement often determines the best choice of device.11-13

Colorimeters measure color according to a set of coordinates (XYZ, or red, green, blue) in a similar way as the human eye does. When you measure color with a colorimeter, you get three values that can be translated to a color point in, for example, the CIE 1931 diagram.

One of the drawbacks of using a colorimeter to measure color is that often the same color can be achieved using different spectrums of light. Colorimeters, therefore, would not be able to tell the difference between several varieties of white light, but this does not mean that the lights are spectrally the same.11,12

Figure 2: CIE 1931 diagram, with the white point marked. Image credit: Admesy.

Spectroradiometers disperse and measure the intensity of each wavelength of light in a light source, providing a spectrum with a ‘truer’ reflection of the color. As a result, spectroradiometers can differentiate between different spectrums of light that all appear the same color, for example different varieties of white light (see Figure 3). 11-13

Figure 3: Spectra of several “white” light sources measured using a spectroradiometer. Image credit: Admesy.13

Both light analysis devices have advantages and disadvantages. While spectroradiometers give a more detailed measurement of the light source, they are often more expensive, slower, and more complex to operate and interpret than colorimeters. Colorimeters offer exceptional repeatability11-13

Colorimeters are very accurate for color measurements and routine comparisons. As a result, they are essential for quality control and are often used in the production and inspection phases of manufacturing. Spectroradiometers, on the other hand, offer a greater degree of specificity, flexibility, and versatility.

Spectroradiometers are the ideal versatile solution for the vehicle research and development process including color formulation and lighting system development.12-15

Color measurement solutions from Admesy

Admesy provides a broad range of instruments focused on color and light measurements including colorimeters and spectroradiometers that are ideal for a range of automotive development and manufacture applications.

The Hyperion colorimeter offers near perfect CIE 1931 filter characteristics combined with high sensitivity and low noise circuitry, resulting in a high-performance colorimeter in a robust and user-friendly system.

For applications that require a spectroradiometer, Admesy offers two options: the Hera series and the Rhea series. The Hera series offers spectral measurement solutions that are compact and robust while maintaining high-performance, while the Rhea series provides flexible, high-end spectral measurement solutions.16-17

References and Further Reading

  1. ‘Fundamentals of Automotive and Engine Technology’ — Reif K, Springer, 2014.
  2. ‘A review on light-emitting diode based automotive headlamps’ — Long X, He J, Zhou J, Fang L, Zhou X, Ren F, Xu T, Renewable and Sustainable Energy Reviews, 2015.
  3. ‘Solid-State Automotive Lighting: Implications for Sustainability and Safety’ — Bullough JD, Sustainable Automotive Technologies, 2012.
  4. ‘The Next Step — Pure Laser High-Beam for Front Lighting’ — Fiederling R, Trommer J, Feil T, Hager J, Auto Tech Review, 2016.
  5. ‘Reality Check: Laser High Beam Performance in Real Driving Tests’ — Albrecht KF, Austerschulter A, Rosehahn EO, 11th International Symposium on Automotive Lighting, 2015.
  6. ‘Influence of ambient lighting in a vehicle interior on the driver’s perceptions’ — Caberletti L, Elfmann K, Kummel M, Schierz C, Lighting Research and Technology, 2010.
  7. ‘Effects of Automotive Interior Lighting on Driver Vision’ — Flannagan MJ, Devonshire JM, The Journal of the Illuminating Engineering Society , 2012.
  8. ‘Colorimetry Applications In The Automotive Industry’ — Chao MK, Hake BP, Electro-Optical Instrumentation for Industrial Applications, 1983.
  9. ‘ Advanced Imaging Colorimetry’ — Konjhodžić Đ, Khrustalev P, Young R, Information Displays, 2015.
  10. ‘11th International Symposium on Automotive Lighting’ — Khanh TQ, Herbert Utz Verlag, 2015.
  11. ‘Colorimetry: Fundamentals and Applications’ — Ohta N, Robertson A, John Wiley & Sons, 2006.
  12. ‘Measuring colour in a world of light’ https://www.admesy.com/wp-content/uploads/AdmesyMeasuringGuide.pdf
  13. ‘Spectrometry: General Spectrometry’
    https://www.admesy.com/application/general-spectrometry/
  14. ‘Visual and Instrumental Assessments of Color Differences in Automotive Coatings’ — Gómez O, Perales E, Chorro E, Burgos FJ, Viqueira V, Vilaseca M, Martínez-Verdú FM, Pujol J, Color Application and Research, 2016.
  15. ‘Hyperion Series’ https://www.admesy.com/product/hyperion-i/
  16. ‘Hera Series’ https://www.admesy.com/product/hera/
  17. ‘Rhea Series’ https://www.admesy.com/product/rhea/

What are Transmission Measurements?

Whenever incident light hits a surface it is either reflected, absorbed, or transmitted. Reflection refers to light which is rejected at the interface and redirected back into the media through which it was already propagating. Absorption refers to the amount of energy lost to the electrons in sample matter as a light wave propagates through a medium. This can cause atomic excitation and subsequent fluorescence. Transmission, meanwhile, is a measure of the light that has traveled through a transparent or translucent material.

Transmission measurements are increasingly important in electronics and life science sectors, with demonstrable applications in thin film, foil, and glass manufacturing. Solutions in cuvettes are also routinely subjected to transmission measurements where both luminous and spectral transmittance may be measured during fluorescence analysis.

This blog post will explore transmission measurements in more detail.

Transmission Measurements of Translucent and Transparent Media

Measuring the transmission properties of transparent media is relatively simple. The spectral and luminous output of a light source is measured as a reference standard or baseline without the interference of the sample. The angle of the incident beam is then used in conjunction with Snell’s law to determine the angle of the beam following transmission. A sensitive photodetector is placed along the path of transmission and both measurements are compared. The difference between the two is used to determine the transmission characteristics of the sample.

Transmission measurements for transparent media are simple because the angle of transmission is easily calculable, and the diameter of the incident beam does not change after diffraction. This allows transmitted light to enter the lens of the detector in its entirety. Translucent materials represent a unique challenge for transmission measurements as the optical properties of the material may cause the incident beam to diffuse and scatter in a multiplicity of directions.

The transmission properties of diffuse and non-diffuse materials vary enormously. They require different sampling technologies to acquire the total transmittance of a sample for spectrophotometric characterization.

Instruments for Transmission Measurements

Transmission measurements are broken into three distinct categories: spectral transmission properties; colour measurement; and optical density. Very few spectrometry arrays can perform all three forms of measurement to the standard of the Rhea spectrometer series from Admesy. It covers a dynamic wavelength range of 200 – 1100nm with a fully-customizable slit size for highly specialized data acquisition.

It is also equipped with a filter wheel capable of measuring optical densities (OD) up to OD 4 and above. OD is calculated as the logarithmic ratio of the radiation intensities incident upon and transmitted by a sample. High OD measurements are challenging for conventional equipment but have found increasing application in various life sciences applications for the quantitation of suspended particles in solution.

The Rhea series is fully configurable and suitable for transmission measurements of varying geometries, including cosine correctors and integrating spheres.

Transmission Measurements from Admesy

Admesy develops optical measurement equipment for OEM integration, display, lighting and appearance measurements in commercial and academic settings. We have supported innovative R&D in technology and life science spaces with an extensive range of spectrometers and light measurement devices.

If you would like any more information about the Rhea series or performing transmission measurements with our measuring accessories, please do not hesitate to contact us.

Colorimetry in perspective of the human eye

Colorimetry is the science used to quantify colour in perspective of the human eye

The science of measuring colour and the appearance of colour is vital: Perception of colour is a subjective process where the brain responds to stimuli produced when incoming light reacts with the several different types of cone cells of the human eye. The way people perceive colour is a subjective psychological phenomenon and is based upon the relation between wavelengths of the light detected by the rod and cone cells and the subsequent processing of those signals by neural pathways. Simply said: the same object illuminated by the same light source can be experienced differently by different people.

Understanding Human Tristimulus Vision
The human eye contains two different types of cells that contribute to human vision. Cone cells operate at high and medium levels of brightness, for example during daytime. Rod cells operate typically under low light conditions, for example at night.

Human tri-stimulus vision is based on three different cone cell types, of which each covers a different wavelength range. Each type of cone cells has a specific spectral sensitivity in short (420 to 440 nm), middle (530 to 540 nm)(M), and long (560 to 580 nm, red) wavelengths. These ranges correspond roughly to blue (S), green (M) and red (L) colours. By combining the stimulation of (mixing) each cell type, we can see different colours.

At night or in the dark, human vision relies on rods as cones are not sensitive enough to provide sight. Rods are in contrast to cones much more sensitive but only come in one type instead of three. This single type has its own typical spectral response with a peak sensitivity around 507 nm. As rods only rely on a specific wavelength range which is not combined with other ranges, human night vision is monochromatic. In other words: the human eye is not able to discriminate colours when it’s dark at night.

The CIE 1931 Colour Space

Although the actual average human eye’s response of S, M and L are known, colorimetry relies on other spectral sensitivity curves. Back in 1931 the International Commission on Illumination (CIE, Commission International de l’Éclairage – CIE in French) developed the still widely adapted CIE 1931 colour space based on a series of experiments. Until then, there was no objective method for describing colour in perspective of the human eye. The CIE model describes colours of any light emitting or reflecting object as a 3-dimensional value of wavelength parts that more or less cover colours we know as red green and blue. These values relate to X, Y and Z respectively and are translated into a two dimensional colour space that covers all colours visible to the human eye.

The CIE 1931 colour space was the first model that linked the distributions of wavelengths in the visible part of the electromagnetic spectrum, and colours perceived by the human eye. One should take into account that this model is, alike any other colour model, a mathematical simplification of human (colour) vision and based on a relatively small population. Still, such colour models allow researchers to define and reproduce colours in most conventional situations and should be considered a tool for measuring colour in applications such as display and lighting industry.

Defining a Standard Human Observer

Considering the fact that human colour perception is fundamentally subjective, it is possible to work with standard human observer to objectively assess an object’s colour. There are a number of standard human observers defined in colorimetry, including the 2° field of vision model as represented by the 1931 model. The 2° standard observer focuses on the high concentration of cones in the fovea whereas the 10° field model uses a broader field of view broadening the visual range. The CIE 1931 model 2° uses chromaticity as a function to describe the two important parameters: hue (colour) and purity (saturation). A complete description of the colour can be provided by measuring the luminance and chromaticity.

Chromaticity itself, also excluding the brightness component, can be plotted in a two-dimensional graph. The CIE 1931 Yxy colour space directly transforms every visible colour the human eye can see into a two dimensional horse shoe type layout. If we consider the colour reproduction capabilities of an RGB emitting source, for example a RGB LED lamp, we can determine the exact area the light source can create. Once we know the colour coordinates of each individual (red, green and blue) LED and plot this into the graph, a triangle can be drawn between these coordinates. This triangle is known as the colour gamut of the source. The exact shape of this gamut entirely depends on the technology of the light source. For example: two different RGB LED light sources may cover a slightly different area as colour points of LEDs of different bins may vary.

 

Example of a colour gamut which is defined by the colour coordinates of three primaries red, green and blue. Any colour within the triangle can be made by mixing the primaries located at the vertices.

Applications of Colorimetry

Colour and colour reproduction has become more and more important with evolving technologies. Technological developments allow even faster and more accurate colour measurement which found its way into many applications. For example brand identity has become more and more important to ensure the right colour reproduction for example on TV. This is directly linked to capabilities of colour reproduction on displays, but also in optimizing differences between different displays. For example the huge technological developments in smart phone displays offers brighter and more vivid colour reproductions, but also requires proper and accurate calibration to ensure the exact same colours amongst millions of phones. For such applications, Admesy has developed in-line production colorimeters such as the Hyperion and 2D imaging colorimeters for full display inspection (Atlas series).

The Changing Landscape of Display Tests

The display sector is characterized by rapid periods of growth and innovation when competing technologies occupy large portions of the same market space. Cathode ray tube displays were supplanted by the rise of lightweight liquid crystal display (LCD) matrices, later on with light-emitting diode (LED) backlights, and now LCDs are experiencing significant market competition from organic light-emitting diode (OLED) technologies.

Modern display tests for ultra-high definition televisions and handheld digital devices are now regularly performed on multiple, fundamentally different technologies. Images on an LCD display are created using a bank of white LEDs and a layered system of polarizers and colour filters, while QD-LED displays typically reduce the requisite number of colour filters and introduce a layer of red and green photo emissive nanocrystals over a backlight of blue LEDs. OLED technologies meanwhile are fabricated from semiconducting materials arranged in a nanomolecular thin-film structure, which emit light organically when excited with electronic signals.

These radically different technologies are also subject to significant further flux in the coming years, with ongoing research into transparent and flexible display technologies, and direct-view QD technology. Will the landscape of display tests adapt to meet the improving capabilities of the display market?

Performing Display Tests on Modern Technologies

The capabilities of the display market are changing radically, but the requirements of display test and measurement equipment has remained largely the same. Accurate light- and colorimeters or spectrophotometers are still required to assess the optical qualities of a display according to the human eye, whether it uses QD, OLED, or LCD technology.

The light-sensitive diode of a photometer is designed to acquire unique optical responses that are closely matched to the average spectral sensitivity according to the CIE 1924 luminosity function Vλ. Usually, tri-stimulus colorimeters are used to cover additional objective optical values in red and blue spectral areas, providing an accurate assessment of a display’s emission spectra for short, medium, and long wavelengths according to CIE 1931. These measurements provide exceptional wavelength definitions and can be acquired by measuring the whole display or assessing individual pixels or spots from the centre to the edge of the image in-line. Display tests typically also include aspects such as Gamma, response time analysis, contrast ratio and flicker adjustment.

Enhanced measurement arrangements can be prepared for multi-spot measurement of multiple optical parameters with outstanding degrees of repeatability. Smart interfaces have been developed to provide simultaneous analysis of the spectral and radiometric characteristics of a display with exceptional degrees of repeatability.

Display Tests with Admesy Products

Admesy is a leading developer of optical measurement equipment for display measurement technologies. Our ever-improving range of equipment is developed to perform precise measurements of a display’s emissive characteristics and closely match those properties to an objective spectral standard. These include:

  • The Atlas 2D imaging colorimeter systems: for comprehensive 2D display tests with luminance and colour measurements adjustable for up to a single RGB pixel;
  • The Hyperion colorimeter series: for highly accurate colour, flicker, contrast ratio and response time analysis.
  • The Cronus spectro-colorimeter series: a hybrid device that allows spectral measurements and built-in XYZ colorimeter for combined colour, flicker, and contrast ratio analysis with a sample rate of up to 50.000 samples per second.

If you would like any more information about performing display tests with Admesy products, please do not hesitate to contact us.

What is a Cuvette Holder?

A cuvette holder is a specialized light measurement accessory designed to maintain high accuracy levels during transmission measurements of liquids. Assessing the transmission spectra of a translucent material is an incredibly sensitive process that requires polymer cells or glass substrates to be handled with extreme care, mechanical stability and cleaned thoroughly between uses. Small molecules and substances such as natural oils can radically affect transmission results, so it is important to avoid all but essential physical contact with a sample cuvette to protect the integrity of gathered data.

What Does a Cuvette Holder Do?

The purpose of a cuvette holder is to suspend a cuvette in a stable position throughout the duration of a measurement process. Both discrete and non-discrete cuvette holders exist for distinct applications, providing the basis for a broad range of incident light analysis. Direct-attachment fixtures can support the analysis of a cuvette’s absorbance and transmission spectra in response to incident light, while discrete cuvette holders can enable optical analysis of the fluorescence of liquid samples when attached to a light source. Leading-edge cuvette holders can also provide a temperature-controlled environment to assess the transmission of a cuvette in distinct thermal conditions and in response to optical fibers. These light measurement accessories are robust and versatile, with an incredible range of applications in the field of light measurement and materials characterization.

Applications for Cuvette Holders

The applications of cuvette holders in transmission, fluorescence and absorption analysis are limitless. Potential substrate materials for thin film electronics, infrared (IR) transmissive foils or industrial tissues, and an enormous range of liquids are often characterized according to their transmission characteristics. Cuvette holders can be used to support a range of transmission tests for industrial solutions and to help calculate the optical attenuation of polymer cells. These capacities vary depending upon the type of cuvette holder and the photometric array it is attached to.

How Are Cuvette Holders Used?

Plastic, glass, and quartz are the most common materials used to fabricate cuvettes for suspending solutions in a transmissive environment. This environment is used to determine the reflection, absorption, and transmission properties of the sample by introducing an incident light and measuring deviations between the spectral transmission characteristics of the cuvette and the reference standard light source. Transmission experiments require a stable light source such as the Steropes LED light source, which provides accurate lighting with an integrated colorimeter to control the light output. Depending on applications and required wavelength range of interest, the Steropes LED is available in standard Royal Blue, Full Spectrum (white) and Natural White. Custom wavelengths are available upon request. All Steropes LED light sources have an ultra-fast stabilization of within 10ms and because of its LED technology, it is suitable for vacuum measurement applications.
In addition to the light source, a spectroradiometer is used to acquire the transmission spectra, while reflection and absorbance must be measured separately or ascertained mathematically by subtracting the sum of transmitted light from that of the incident light. The nature of the transmitted light can support distinct conclusions about the physical characteristics of the observed material, with diffusive and non-diffusive attributes requiring distinct optical detectors for optimal data acquisition. This arrangement can be used to determine the transmissive response of a material for each individual wavelength and to measure its optical density.

Cuvette Holders with Admesy

Admesy is an expert in light measurement and optical equipment, providing an extensive range of photometric equipment and optical measurement accessories for distinct applications. Our catalogue includes an cuvette holders for transmission measurement applications as well as many other optical measurement accessories. Explore our full range of light measurement accessories, or contact us if you would like any more information.

Measurement Instruments for Luminous Intensity

Light measurements can be divided into a series of measurement principles, each of which is quantified according to different optical parameters. Photometric measurements, for example, are expressed according to the responses of the human eye. This is based on an averaged spectral sensitivity known as the Vλ luminosity function, which categorizes wavelengths of green-yellow light of approximately 555nm as the concentrated peak sensitivity of human vision in bright conditions.

Photometric measurements are concerned with the luminous power (lm), illuminance (lm/m2 or lux), luminance (cd/m2), and luminous intensity (cd) of a light source. In this blog post, we will explore luminous intensity in further detail, and explore some of the appropriate light measurement instruments for assessing the intensity of a lighting product.

What is Luminous Intensity?

Luminous intensity, often misinterpreted as brightness, is the quantity of wavelength-weighted power of a light emitted per unit solid-angle. It is expressed as a unit of candela (cd) and is measured according to the Vλ luminosity function. The luminous intensity of a light source is distinct from its luminous flux, which measures the power output according to Vλ of a light source in all directions, and is expressed in lumens (lm).

This distinction highlights the semantic difference between brightness, luminous flux, and luminous intensity – the latter of which refers to the optical power output in a defined field of view. Luminous intensity is particularly important for measuring high-power light-emitting diodes (LEDs) and solid-state lighting (SSL) for domestic and commercial spotlights. Quantifying the optical output of a directional light source against an averaged human sensitivity is a critical process for development, manufacture, and quality control of commercial LEDs and SSL.

Measurement Instruments for Luminous Intensity

For optimized response, luminous intensity measurements are carried out in isolation without interference of ambient lighting. Measurement instrumentation is commonly used to acquire multiple photometric measurements to assess the broad optical characteristics of a light source. Photometers capable of carrying out luminous intensity measurements must be equipped with either a cosine corrector or an integrating sphere in 2π configuration. The first however is the most compact and thus most practical solution.

Cosine correctors acquire light across a 180° field of view with a Lambertian response and diffuse it, while integrating spheres reflect obtained optical signals around an internal cavity into a sensitive detector. Spectrophotometers can use either of these geometrical configurations to determine the luminous intensity of an LED or SSL product.

Luminous Intensity Measurements with Admesy

Admesy provides a substantial range of photometric measurement instruments and accessories for luminous intensity measurements of a range of commercial and professional lighting products. Depending on the need for measuring multiple parameters, Admesy has multiple options, providing fully-rounded analysis of the optical characteristics of lighting in throughout the production process.

Our measurement instruments capable of acquiring luminous intensity data when equipped with cosine corrector include:

  • Rhea series spectrometer;
  • Hera series spectrometer;
  • Cronus series spectro-colorimeter;
  • Astera series light meter.

If you would like any more information about performing luminous intensity measurements with Admesy products, please do not hesitate to contact us.