All posts by caesus

Using Light- and Colorimeters for Spot Measurements

Modern displays are subject to optical variations at different stages in the production process. Colour and luminance quality can fluctuate due to light-emitting diode (LED) batch inconsistencies or quirks, but this does not necessarily constitute component failure. This could merely be a product of the rapid-throughput production cycles and the complex arrangements of LED backlights, polarizers, and colour filters in display products. Some variation at the development stage is to be expected. In fact, these variations regularly inform the necessary optical adjustments before a product is consumer-ready.

Asteria Light Meter

Light- and colorimeters acquire the variation data through spot measurements, where a single (representative) spot is analyzed respectively to the rest of the display. Information pertaining to display luminance and colour uniformity amongst batches can be obtained from both large and small displays by dedicated light- and colorimeters. This is performed by analyzing the central point of the display, or several spots across the surface to provide referential information about uniformity over different spots. One or more devices may be used throughout this process, depending on the measured spot size and display size.

To obtain the broadest possible range of relevant display information, spot measurements are regularly carried out using a combination of colorimeters which are calibrated against other optical measurement devices such as spectrometers. Luminance and flicker-only measurements can also be carried out using a light meter. This article will explore the performance of spot measurements using measurement equipment and associated accessories in more detail:

Spot Measurement Analysis Using Colorimeters

Display development and manufacturing professionals commonly carry out accurate spot measurements tests to ensure that products perform to advertised specifications and have a perfect inter-device colour rendering repeatability. These tests include colour analysis at one or more spots, white point adjustment, flicker adjustments and response time determination.

The Hyperion series is alike the successful MSE series tri-stimulus colorimeter equipped with a lens system that captures data from a specific spot on a screen. Typical colorimetric data can be acquired according to CIE 1931 XYZ and Yxy as well as flicker data according to JEITA and VESA flicker standards.

For more basic display analysis that only requires luminance or flicker measurements, the Asteria series equipped with a collimating lens offers the best price-performance ratio. Offering absolute luminance according to V(λ) and flicker data including standard metrics such as flicker percentage and index as well as JEITA and VESA flicker methods. With its high sample rate of 186.567 samples per second, this compact device can quickly and reliably perform in-line spot measurements of displays, providing insights into batch consistency and informing any necessary adjustments.

This light meter can be combined with multiple spectrometers or colorimeters for quick pre-inspection and extended capacities.

For multi-spot measurement applications, such as typical 9-point display measurements, the Medusa series device controller has been developed. The Medusa is a smart interface solution for controlling up to 16 devices simultaneously. Light- and colorimeters such as the Asteria and Hyperion can be connected in parallel to perform synchronized measurements. This enables manufacturers to perform numerous optical spot measurements simultaneously, reducing tact times and enhancing repeatability without the need of moving measurement equipment in front of a screen.

Light- and Colorimeters from Admesy

Admesy is a leading supplier of optical measurement equipment for a range of applications, from laboratory testing to industrial manufacture with demanding commercial requirements. Our light- and colorimeters are equipped to provide rapid insights into the optical intensity of displays of varying sizes, with full-integration through numerous operating systems and high degrees of functionality with complex arrays of measurement devices.

If you would like any more information about performing spot measurements with our light- and colorimeters, please do not hesitate to contact us.

Outlining the Applications of a VIS Spectrophotometer

A VIS spectrophotometer is a quantitative tool for analyzing the visible spectral properties of a sample with outstanding degrees of accuracy. It can acquire the intensity of a light source at wavelengths of between 380 – 780 nm, with integrated processors capable of running independent calculations and providing rapid assessments of a lighting product’s spectral output. Multiple configurations of VIS spectrophotometers exist to enable precise measurements of visible spectra from numerous lighting products requiring specific metrics.

This article will explore the applications of a VIS spectrophotometer in more detail.

Spectro-Colorimeter

Display Measurements with VIS Spectrophotometers

The hardware of a VIS spectrophotometer can accurately assess the correlated colour coordinates according to CIE definitions of a display. The main application for measuring displays with spectrophotometers is to calibrate relatively faster colorimeters used in production lines on target displays, to ensure an overall uniformity between screens of different batches.

The Cronus series VIS spectrophotometer from Admesy is capable of calibrating its own built-in tri-stimulus colorimeter and perform high-speed colorimetric measurements based on spectral accuracy. It can be used for R&D of emerging display technologies, or quality control of end-products in sites where multiple different display technologies are monitored.

LED Measurements with VIS Spectrophotometers

Light-emitting diodes (LEDs) are one of the most broadly used components in the world, with applications in industrial, commercial, and domestic sectors. While LEDs are easy and affordable to produce, differences between batches are inevitable due to the production processes. Binning LEDs is useful to ensure uniformity and consistency in lighting products.

Light Bulb Measurements with VIS Spectrophotometers

The colour rendering index (CRI) refers to a light source’s capacity to accurately reproduce the colours of objects respective to natural (day)light. A high CRI value is attractive for applications where accurate colour reproduction is required. This may not only be important for general interior lighting but in particular for (fashion) retail.

VIS Spectrophotometers from Admesy

At Admesy, we provide various VIS spectrophotometers for mid and high-end applications. Mid-range Hera series spectrometers are available in three wavelength ranges and different optical configurations: lens systems typically applied in display measurements, cosine correctors for lighting applications and fiber versions allow remote sensing and connecting to accessories such as integrating spheres.

In addition, Admesy provides the world’s first VIS spectrophotometer combined with an innovative tri-stimulus colorimeter. This allows users to alternate between robust spectral information and high-speed colour and flicker measurements, providing a broad range of measurement capacities with a sample rate of up to 186.567 samples per second. The Cronus series is available in three distinct specifications, equipped with either fiber connections, a lens, or cosine correctors for specific applications.

For high-end high dynamic range spectral measurements that also require accurate spectral measurements at low luminance levels, the Rhea spectrophotometer is the ideal measurement solution. With various options in slit size, grating and desired wavelength range, the Rhea is the world’s most affordable one-off configurable spectrophotometer.

If you would like any more information about our world-leading VIS spectrophotometers, please do not hesitate to contact us.

EPIC interviews Admesy CEO Steven Goetstouwers.

Unlike most CEOs of European photonics companies, Steven Goetstouwers is neither an engineer nor does he have a technical background. A native of Belgium, he studied at the University of Hasselt in Belgium and took a degree involving a mix of business and technical courses but with the main focus on entrepreneurship. Click here to read the full article.

The Capacities of Compact Spectrometers

The rapid pace of modern technological research, development, and manufacturing has altered the way many crucial processes are carried out. R&D measurements and quality control procedures are increasingly integrated into continuous production facilities to improve manufacturing throughputs and provide accurate product insights directly at the point of production. This requires instruments that are smaller, with improved functionalities over established measurement equipment tailored for specific needs in production lines. In lighting and display manufacturing environments, this challenge is overcome by the application of compact and robust spectrometers.

Spectroradiometer

A compact spectrometer is a sturdy light measurement instrument that encompasses multiple spectral measurement capacities in a small and versatile housing. They can be equipped with application-specific components such as a fixed lens or a cosine corrector, or fiber optics for remote measurement sensitivity – but can compact spectrometers perform to the same demanding levels as larger light measurement components?

This article will explore the applications and capacities of compact spectrometers in more detail:

Display Compact Spectrometers

The range of modern display technologies introduces consumers to dynamic, light-intensive images of varying spectral outputs such as LCD and OLED technology. By LCD screens, it is accomplished by a matrix of thin film materials or liquid crystal display (LCD) layers over light-emitting diodes. These diodes provide all the light necessary for the polarizers and colour filters to create distinct optical characteristics from pixel to pixel.

Compact spectrometers are routinely used to optimize the properties of display components and ensure batch to batch consistency through quality control processes. The Hera series compact spectrometer for display applications is equipped with a fixed lens of either 5, 10, or 20 mm, or with stable fiber optic connections. These can acquire measurements across a spectral range of 380 – 780 nm, with an optical resolution at full width half maximum (FHWM) of 2.3 nm. This exceptional degree of optical acquisition is crucial for modern HDR displays.

Lighting Compact Spectrometers

The Hera series compact spectrometer for lighting measurements is equipped with a 5, 10, or 20 mm collimating lens or a cosine corrector, or fiber connector for remote sensing or connection to an integrating sphere for absolute spectral measurement across three distinct ranges. Typically, LED light measurements are concerned with optical characteristics on the visible spectrum, from wavelengths of 380 – 780 nm. The VIS Hera series can determine the spectral output and colour values of visible light in a couple of milliseconds, depending on the light level. An enhanced UV-NIR range version enables researchers to obtain wavelength data from 200 – 1100 nm.

The excellent functionality of the Hera display spectrometer for both display and lighting applications is augmented by a high-speed processor capable of internalizing all required calculations for compensation and calibration. Data is delivered with guaranteed accuracy every time, with compensations for dark current, linearity, wavelength calibration, and absolute calibration in just 14 ms. This data processing speed immediately improves upon larger spectrometers, and removes the requirement for many external calculations.

Larger spectrometers typically encompass wider spectral ranges than compact spectrometers. However, smaller light measurement systems that perform to exceptional levels in distinct measurement parameters such as CRI, CCT, radiometric, and photometric, can compete with more conventional materials through their ease of access and exceptional performance in the areas that matter most.

Compact Spectrometers from Admesy

Admesy is a leading supplier of light measurement instrumentation for a range of research and manufacturing applications. Our compact spectrometers are available with multiple configurations for application specific requirements, and robust housings capable of surviving the exacting conditions of manufacturing environments.

If you would like any more information about our Hera series compact spectrometers, please do not hesitate to contact us.

The 4 Most Common Spectrometer Applications

Spectroradiometers are used to separate, quantify, and analyze the spectral characteristics of a light source, providing industry-specific insights based on a light’s wavelength intensities or frequency. They use a grating to split light into wavelengths of different bandwidths and funnel that light through the spectrometer using integrated concave mirrors. These high optical throughput components ensure a maximum amount of sampled light reaches a high sensitivity sensor for analysis. High-end spectrometers may even include a series of optical filters or a filter wheel to improve the equipment’s wavelength range, enabling a higher dynamic range of light over the entire wavelength range of the device.

Rhea Spectrometer Inner Workings

Spectrometers are used in numerous industrial and commercial sectors, where precise lighting parameters are vital for meeting product specifications or health and safety regulations. This article will explore the four most common applications of spectrometers in some more detail:

Display Spectrometers

Display technology has grown exponentially in recent years, with emerging technologies such as organic light emitting diodes (OLEDs) challenging the conventional liquid crystal display (LCD) market. Digital devices such as smartphones, tablets, and televisions are subsequently built with more vibrant and dynamic displays than ever before. Spectrometers have been instrumental in supporting this period of growth and innovation, finding use in process and quality control applications.

The Rhea series advanced spectrometer is routinely used during the production of LCD and OLED based display technologies as a master instrument to adjust the display’s optical characteristics and maintain exceeding levels of batch-to-batch consistency combined with several colourimeters like the Hyperion or MSE series.

Lighting Spectrometers

Light emitting diodes (LEDs) and solid-state lighting (SSL) have effectively supplanted halogen and fluorescent bulbs due to their superior levels of efficiency and tuneability. It is increasingly possible to fine-tune the optical characteristics of LEDs and SSL to display distinct aesthetic characteristics, such as dimming or changing colours. This is all enabled through improved interconnectivity between devices, greater digital driver quality, and fundamentally better light measurement technology.

Spectrometers are crucial for enabling the growth of LEDs and SSL, by maintaining exceptional optical characteristics or products throughout production, thus enabling new functionalities. The Rhea series spectrometer is capable of measuring for multiple lighting parameters, including spectral power distribution, colour, and colour rendering properties. These parameters can, for example, be used to match white points of different LED luminaries between product batches

Spectrometers for Analysis Solutions

The analysis of a translucent materials’ optical qualities requires highly accurate spectrometry equipment, often integrated as a system with additional devices like stabilized light sources to ensure optimized stability between measurements. More advanced types of these measurements include measuring the fluorescence or reflectiveness of samples and light sources can be quantified by coupling a highly sensitive spectrometer with a stable light source and measuring the differences or spectral changes between incident light and that which is transmitted or attenuated. These analytical methods may be applied for the characterization of materials or layer thicknesses of anti-reflective coatings on translucent materials.

Admesy’s Rhea series high-end spectrometer integrates multiple calculation methods within the device, reducing processing power for analytical methods that require multiple energy-intensive processes.

OEM Spectrometers

Original equipment manufacturers (OEM) commonly rely on light measurement specialists to provide suitable spectrometers for integration with their own innovative machinery. The potential applications for OEM integration of spectrometers are significant, which is why high-end spectrometry equipment is increasingly equipped for flexibility and configurational variation. This enables individual customers to configure the spectrometer to their unique specifications, gaining the full potential of the measuring component and improving the functionalities of their own products.

The Rhea series is built to be fully integrational with OEM, with a broad wavelength range of 200 – 1100 nm depending upon the product application.

Spectrometers from Admesy

Admesy prepares advanced spectrometers for numerous commercial sectors, providing solutions for R&D, process control, and product innovation. If you would like any more information about the Rhea series, or any of our other spectrometers, please do not hesitate to contact us.

What Causes LED Flicker?

Mains electricity for residential and commercial properties operates on the principle of alternating current (AC); the process by which an electrical current and voltage is periodically reversed in an oscillating motion known as a sine wave. The sine wave constantly moves from negative to positive values in association with the magnetic polarity of the alternator generating the electricity. This fluctuating process enables high power propagation over long distances, but it also causes lights to rapidly switch on and off – or flicker. It depends on the type of light source whether this switching is noticeable or not. For example, incandescent lamps are too slow to actually respond to sine waves of the mains.

Flicker of LED lights is primarily determined by the power frequency of the mains supply, for example the UK’s mains frequency is 50 Hz, which describes an alternating cycle of 50 oscillations between negative and positive poles per second. The potential flicker frequency in a broad range of simple LED light bulbs is subsequently double the power frequency, 100 Hz and caused by rectifying AC power.

While these fluctuations are inherent in the methodology of AC power supplies, flicker can also be caused by driver or software-related issues.

Studies have shown that the human eye can perceive flicker of LEDs at rates of up to 90 Hz, and anything above that is imperceptible to the human eye. Generic lighting tends to operate at frequencies of 50 – 90 Hz, which is designed to illuminate an environment and give the impression of a stable and constant light source – even though the LEDs are consistently switching on and off hundreds of times per minute.

Further studies have shown that flicker rates of up to 500 Hz can result in unintentionally hazardous stroboscopic effects, while the perceived flicker of up to 70 Hz can result in:

  • Seizures;
  • Headaches, fatigue;
  • Blurred vision, eyestrain;
  • Reduced visual task performance.

However, visible flicker is not merely a result of frequency. It is determined by an index of factors including an LED’s peak intensity and the shape of its waveform (e.g. PWM), using various values to acquire a light source’s flicker percentage (0 – 100%), its flicker index (0 – 1.0) or IEEE PAR 1789. Measuring these varying parameters typically requires optical instrumentation enabled with CIE 1931 response sensors according to Vλ.

Flicker Measurements from Admesy

Admesy are leading designers and manufacturers of light measurement equipment for a broad range of applications, with dedicated instrumentation designed to measure lighting products at all stages of the production process.

The Asteria series is a high-speed light measurement device capable of sampling a light source at speeds of up to 186,567 samples per second and is capable of measuring flicker as a percentage or index values as well as newly developed standards/recommendations that take into account multiple frequency components and their modulation.

If you would like any more information about our flicker measurement products, please do not hesitate to contact us.

The Light Measurement Accessories from Admesy

The performance of accurate light measurements is contingent on the measurement accessories implemented in the analytical components. A high-end spectrometer requires excellent optical sampling equipment to accurately assess the chromaticity or intensity of a given light-emitting source.

Admesy develops, manufactures, and supplies a broad range of measurement accessories capable of integrating with our full catalogue of products. This article will explore some of these measurement accessories in more detail:

Optical Sampling Accessories

Optical sampling is the fundamental principle of light measurement equipment, and the acquisition of varying optical metrics requires the application of suitable lenses, probes, and spheres. Admesy has developed a wide selection of optical measurement accessories, from lenses to more specialized equipment, including:

  • Collimating lenses, which actively focus beams of light or photons across a determined field of view into parallel trajectories – these are commonly applied for spot measurements of homogeneous lit surfaces like displays or OLED panels;
  • Cosine correctors; light diffusers linked to optical fibers, which can collect and redistribute light acquired across fields of view up to 180° with a Lambertian response;
  • Integrating spheres; hollow spherical cavity designed to collect light emitted from various angles – these are capable of generating a homogeneous light distribution;
  • Reflective probes, which use robust fiber connections to remotely measure wavelengths of light to determine and analyze the colour of a given surface under 0/0 or 45/45-degree geometry;

Each of these measurement accessories is widely available for use in light measurement systems for industrial, commercial, and academic environments.

Medusa Series Controller Platform

The Medusa platform is an integral measurement accessory for production or manufacturing environments, in which multiple light measurement devices like colorimeters are used to perform multi-spot measurements. For example, typical 9 point measurements taken in display industries. This smart controller is designed to manage and synchronize up to 16 Admesy light measurement units simultaneously, offering extraordinary improvements to measurement options by allowing for isolated usage of single devices, or specific device groupings to carry out multiple light measurements at once.

This measurement accessory is available with 4, 8, 12, and 16 USB inputs, supporting the light meter, colorimeter and spectrometer product range currently available. It also features a high degree of automation thanks to a sophisticated, built-in operating system.

Light Measurement Accessories from Admesy

Admesy are industry-leading designers of various optical measuring equipment, providing instrumentation capable of accurately assessing photometric qualities such as fluorescence, luminance, luminous intensity, and chromaticity. Our light measurement accessories are trusted to perform robust and rapid measurement processes to ensure lighting is of the highest standard for limitless applications.

If you would like any more information about our measurement accessories for optical measuring applications, please do not hesitate to contact us.

Illuminance Meters for Professional Applications

Illuminance meters quantitatively measure the amount of luminous flux (lx) of incident light on a surface according to human perception; CIE 1931 function. This is crucial for the optical optimization of lighting designed to fulfill an environment’s ambient properties, for example for retail, offices, and workspaces. Illuminance measurements can be carried out to achieve a particular atmosphere and to ensure that lighting conditions are compliant with various health and safety protocols.

Innovative light meters can perform one of the most basic light measurements to comprehensively improve the optical qualities of various light sources, including: illuminance & luminous intensity measurements and high-speed flicker measurements for LED-based lighting.

This article will explore Admesy’s illuminance meters in more detail, exploring how they can improve the conditions of a broad cross-section of professional locations:

Asteria Series Industrial Light Meter

The Asteria is a rapid light meter with additional light measurement parameters. It is calibrated for absolute illuminance measurements with an integrated cosine corrector featuring an illuminance sampling range of 10 – 150,000 lux, which is accurate to within +/- 2% of the measured value. These specifications allow the Asteria series to be used in production lines of various types of light sources to perform a 100% inspection rate of product batches. It can further improve the production process by determining any changes in the process directly, increasing yield and customer satisfaction.

This compact illuminance meter is also capable of analyzing flicker to widely-used flicker standards including flicker percentage and index. Newly developed flicker recommendations such as IEEE PAR 1789 are also supported, and by using raw flicker data any internal or upcoming standard can be implemented easily.

Illuminance Meters from Admesy

Admesy is a leading developer and supplier of light measurement equipment for industrial and R&D applications, with a broad product range capable of determining various optical qualities of manufactured light sources.

Our catalogue of devices capable of measuring illuminance also includes:

  • The Rhea series spectrometer: a flexible spectrometer with variable optical systems;
  • The Hera series spectrometer: a compact series of spectrometers with multiple spectral ranges.
  • The Cronus series spectro-colorimeter: a combined spectro-colorimeter that attains highly accurate spectral data as well as high-speed XYZ and flicker measurements.

If you would like any more information about our lighting measurement devices, including our illuminance meters, please do not hesitate to contact us.

The Importance of Light Measurement in the Display Industry

The display industry is characterized by persistent innovation and competition, as manufacturers strive to deliver the best possible user products. Various industry leaders field contending new display technologies such as QLED (quantum dot light emitting diode) and OLED (organic light emitting diode) displays in bids to provide the best consumer experiences and improve their own share of the display market – and that market is immense.

One of the most common applications for digital displays in terms of use is for mobile phones, and currently, as many as 6 out of 7 billion people on the planet are estimated to have access to a mobile device – alongside ownership of display devices such as TVs and computers.

This broad range of applications has resulted in an incredible market saturation, which necessitates highly-accurate light measurement that ensures products in the public domain are fit for purpose. The fast-moving, large batch manufacturing processes of various digital displays also require rapid and efficient quality control testing to ensure batch-to-batch consistency.

This article will explore some of the issues that precise light measurement instrumentation can detect for display products:

Spot Measurements

Spot measurements can be implemented for both small and large displays throughout the production process to counter colour and luminance (cd/m2) variation across the surface, allowing for the early application of appropriate filters to adjust and optimize the end-products optical characteristics. It is a form of light measurement that analyzes a spot or several spots across the display to determine the colour of the panel.

Light measurements of this caliber are designed to keep up with the speed up manufacture for high-end products while increasing product yields. They are also integral to the release of displays that consistently perform to given technical specifications, thereby improving customer satisfaction.

Modern consumers are increasingly aware of the improving technical capabilities of displays, and consequently of the various products offered by competitors across the market. It is important for display companies to implement thorough light measurement protocols to ensure display products perform to an advertised standard.

Admesy offers various light measurement devices tailored to production processes, which also conform to the latest industry standards in terms of speed, accuracy, and production-friendly integration. The product line for display spot measurements includes high-speed colorimeters like the MSE series, and the Hyperion colorimeter, which features near-perfect CIE 1931 XYZ filter characteristics. In addition to tri-stimulus colorimeters, spectrometers like the Rhea and Hera have been designed to operate in display production lines with high accuracy. A hybrid device, the Cronus, combines the speed of a colorimeter and spectral data of a spectrometer in one user-friendly device.

2D Measurements

2D imaging measurements analyze a display in its entirety by capturing an image with a camera that is calibrated with a built-in spectrometer, or through a three-stage process with XYZ filters applied to the entire screen. These 2D imaging spectro-colorimeters can be used to test various displays including LED panels and OLED panels, with general purpose applications for luminous surfaces.

Luminous surface displays are increasingly implemented in commercial and retail environments to create dynamic ambient atmospheres, or for targeted, colorful advertisements – yet they must also perform to stringent requirements. These surfaces must be accurately tested and monitored for flicker, to comply with various health and safety requirements dependent upon where the surface will be installed. Light measurements capable of detecting flicker in luminous surfaces can subsequently help improve various environments for workers, consumers, and pedestrians.

The Atlas system from Admesy is an imaging colorimeter capable of performing 2D light measurements with an exceptional degree of flexibility. It combines a calibrated spectrometer and a rapid sampling light meter for the precise determination of flicker, alongside multipoint luminance and color measurements down to a single sub-pixel.

Light Measurement Products from Admesy

Admesy has been providing high-quality light measurement systems and equipment to customers for over a decade, offering accurate solutions to emerging and established problems in various industries.

If you would like any more information about our light measurement equipment for the display industry, please do not hesitate to contact us.

Performing Advanced Spectral Measurement with Admesy Spectroradiometers

A spectroradiometer is designed to accomplish spectral measurement across a wavelength ranges based on an absolute calibration. This calibration allows accurate and precise determination of distinct radiometric, photometric, and colorimetric characteristics of a light emitting object by measuring and analyzing its spectral power distribution. This singular spectral measurement method can perform with complete autonomy within a robust and compact housing suitable to various industries, providing accurate insights into both photometric and spectroradiometric values.

This article will explore the process of performing advanced spectral measurement with Admesy spectroradiometers in more detail:

How Spectroradiometers Perform Spectral Measurements

The observation of the light output of an object is first captured by sensitive optic equipment which allows a spectroradiometer to capture light of different wavelength ranges from varying fields of view, to differing degrees of control. The three primary optical component options for spectroradiometers are:

  • A (collimating) lens, which allows users to determine the field of view by narrowing rays of light to make (parallel) beams;
  • A cosine corrector, which allows users to acquire and redistribute light from a 180° field of view with a Lambertian response;
  • An integrating sphere, which features a reflective cavity around or in front of the light input to maximize the efficiency of the device.

After passing through an optical configuration, such as a lens, the light enters the spectrometer through the slit. The dimensions of this slit regulate the amount of light entering the optical bench and this affects the optical resolution of a spectroradiometer. A concave mirror [M1] reflects the divergent incoming beam into a collimating beam towards the grating where dispersion of the light takes place. Admesy’s Rhea uses a reflective grating: the collimated light beam is dispersed into different wavelengths upon reflecting on the grating. Different wavelengths reflect on the grating under different angles, creating multiple divergent beams. A second concave mirror [M2] reflects and focuses the different separated wavelengths towards the detector.

Spectral Measurement

The optical bench of a spectrometer is designed in such a way that particular wavelengths are focused on specific pixels of the sensor. By verifying wavelengths and assigning pixels to specific wavelengths the device is wavelength calibrated: signals picked up by a pixel are linked to a specific wavelength and this results in a device known as a spectrometer. A second calibration step is necessary as not every pixel responds the same way to the true intensity of a wavelength. For this reason, it is important to determine the correct proportions for each pixel. This second calibration step is achieved by calibrating against [calibration] light sources such as a NIST traceable lamp. Such light sources come with datasheets on their spectral distribution in absolute values. Once the results from the spectrometer are matched towards the known results of a standard light source, the device is entirely calibrated and ready for absolute and accurate measurements. After this calibration step, the device is known as a spectroradiometer. Besides the radiometric quantities, a spectroradiometer can also measure colorimetric and photometric quantities very accurately if it covers the VIS range. Spectroradiometers that cover the 380-780nm VIS range only, are also known as spectrophotometers.

Spectroradiometers from Admesy

Admesy has also applied its vision on compact, robust design with excellent measurement capabilities towards its range of spectroradiometers. Their design allows them to be used from research & development applications to continuous use in production lines. The spectral range covered by Admesy products currently covers the 200-1100nm range with limitless options in custom wavelength range, slit size and resolution and optics for a wide range of applications.

If you would like any more information about our spectral measurement products, please contact us.