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2018-08-23

OL0050–HSBS, highly sensitive spectroscopy for countless applications

OPTO4L remains true to its principles!

Theoretically, optical spectroscopy delivers very detailed information about the energy distribution within a specified wavelength range. It enables, for example, measurement of color and brightness values within the visible range of light of flat screens, white and monochrome LEDs, but, above all, of RGB or even multicolor LEDs at very high precision and conforming to standards (CIE 1931, CIE 1976, CIE 2015, etc.).

In other applications, where rather than the light sources themselves, their light remitted by objects is measured, spectroscopy allows to make a precise statement about whether an object’s color value conforms to standards (e.g. CIELAB color space) or about any color error that the object has in relation to a specified color value (ΔE, ΔE 94, ΔE 2000, etc).

Especially in these applications, generally referred to as ‘color measurement’ or ‘color sensing’, spectroscopy is able to display another strength – in particular compared to filter-based solutions: tristimulus values only apply when also stating the illuminant (a standardized light source) such as D50, D65 or F-type for fluorescent light sources as often specified for office and work lights.

The results obtained using a spectrometer enable to simply determine the color value of any given illuminant in a mathematical way, whilst filter-based measuring instruments – even comparatively complex XYZ sensors – can only deliver results for a single illuminant (and already this requires elaborate calibration of the XYZ sensors).

This is nothing new and there are already many providers of optical spectrometers in the market!

That’s right! And the growing demand for high-resolution analytical instruments, providing increasingly precise measuring results, also leads to new and ‘better’ instruments being launched into the market. Apart from the very high acquisition costs of such measuring instruments, the form factor also makes it difficult, or even impossible, to integrate them into systems and processes outside of the laboratory environment.

However, modern production processes in biotechnology and environmental technology, as well as pharmacy, industry, chemistry, food technology and agricultural technology, are actually based on the continuous availability of critical process parameters, e.g. in order to implement closed-loop processes or to be able to respond to safety indicators in good time.

The major progress achieved in MEMS technology in recent years also reflects in the field of optical spectroscopy with a growing number of extremely miniaturized components. On the one hand, this trend fuels the potential users’ demands in the aforementioned areas, because basically it opens up numerous possibilities in terms of form factor and price nobody would have dared to think about before! On the other hand, we see that complete systems based on these components are still very much a rarity and, as a result, the use of such miniature spectrometers is all too often still limited to optics and electronics experts.

Both emission and reflectance measurement within the visible range of light is a variation of the general application area of radiometry. Simply put, it focuses on the quantitative measurement of light within a very broad wavelength range.

This may sound rather mundane; however, a broad range of possible applications can be implemented using adapted constructions! They include general laboratory and process analytics, environmental and agricultural technology as well as chemistry, pharmacy, biotechnology, industry and many more. RAMAN, fluorescence and absorption spectroscopy allow testing of materials such as plastics for their desired composition, identification of toxic substances, determination of environmental pollution, testing of lubricant quality, authenticity verification of high-grade edible oils, wines and coffee and many more applications.

The specialists working in all these areas know their products and processes inside out. Yet, they are rarely experts for optical metrology at the same time! This is where OPTO4L GmbH and its growing product portfolio come in. We implement systems on the basis of the latest miniaturized components, transferring optical analytics from the laboratory to the production line and even into the field.

Okay, but what is so special about the OL0050-HSBS spectrometer?

In applications with a low-intensity light source, measuring times can quickly add up to 10 seconds or a multiple thereof. This already applies to high-priced desktop and laboratory equipment, e.g. incorporating elaborate back-thinned CCD sensors requiring special cooling used to try to increase the signal/noise ratio and sensitivity. This is all the more true for the miniature spectrometers!

In the area of display calibration, for example, this causes obvious problems. Depending on requirements, up to 100 and more colors need to be measured. The measurements, especially for gray scale optimization, are very time-consuming, as they involve only dark and very dark colors (through to ‘black’). Therefore it is easy to see that a calibration in mass display production remains a major issue to this day and, as a result, is usually not performed despite the existing demand for it.

Another problem with miniature spectrometers usually is the lack of a standardized optical connector. The end user has to take care of it himself and runs a high risk of getting it wrong by making incorrect adjustments.

Another limitation of established miniature spectrometers is quickly overlooked in many applications – usually, the optical resolution is significantly above 10nm (also due to the miniaturization). This makes the measurement of non-broadband spectra more unreliable. This applies to the measurement of monochrome LEDs, but even more so when measuring RGB and RGBW LEDs. Applications like automotive lighting and also aerospace are seeing a strong increase in the demand for metrology equipment and controllers for the calibration of lights based on a mix of colors. Understandably, measuring time is an absolute knockout criterion in mass production, also because the technology used requires every single light to be measured and calibrated individually, at least in the high-end segment!

Numerous manufacturers of miniature spectrometers (and also laboratory equipment) enable a significant improvement of the optical resolution by selecting an appropriate input slit width of the spectrometer. This, however, results in a disproportionate negative impact on sensitivity which takes us back to the initial problem of lacking sensitivity and long measuring times.

Lastly, there is another problem with many miniature spectrometers that can produce ‘odd errors’ in some applications. This is especially the case with the aforementioned RGB LED applications (or generally speaking, light sources based on additive color mixing). Usually, the individual colors are controlled using PWM modulation with frequencies of a few hundred hertz. It is invisible to the human eye, but technically detectable. If the detector used in the spectrometer does not have an ‘electronic shutter’ (ensuring that all pixels are exposed and also evaluated simultaneously), the PWM modulation will not only result in increased ‘noise’ in the measured intensity, but at the same time in a ‘spectral noise’, similar to a constant change in color. This is extremely counterproductive, especially when a specific color needs to be calibrated! Although the negative effects of PWM can be reduced through averaging as required, this will inevitably result in overall longer measuring times.

With the OL0050-HSBS, we continue to follow OPTO4L’s corporate philosophy which provides the foundation for all our product developments: one instrument for as many different applications as possible.

  • Providing a sensitivity that is by several orders of magnitude higher than other miniature spectrometers (factor 100 and more), comparable to desktop equipment
  • The latest CMOS detector technology with electronic shutter and active pixels
  • Optical resolution significantly below 10nm (~7nm at 550nm)
  • A continuous wavelength range of 360nm – 1000nm (~340nm to ~1090nm usable)
  • Monolithic optical design for high wavelength stability
  • Averaging of up to 16 in the ‘hardware’ (precisely timed recording and storage of individual measurements in the instrument)
  • Control of an external light source for synchronous measurement, e.g. for general color measurement or fluorescence and RAMAN applications
  • Trigger input, additional optional outputs
  • Internal temperature sensor
  • Integration times of between 100us to 60 seconds
  • Measurement of asynchronous flashlights (e.g. mobile phone and camera flashlights) with automatic starting pulse acquisition. Readout of up to 16 sequential and precisely timed individual spectra
  • Elaborate, achromatic optical probe for parallel beam path and high reproducibility (enables precise intensity calibrations)
  • Open, flexibly usable software interface with ASCII-based protocol (also usable via terminal)
  • Fast RS422 interface, a full spectrum can be read out in less than 250ms
  • Very broad supply voltage range from 5V to 28V, incl. power supply via USB interface only (with OL0072 interface). As a result, it can easily be used as a component in embedded systems (e.g. laboratory automation in the field of miniaturized bioprocess engineering)
  • Combined with OL0072, it can also be used without an additional supply with a tablet or mobile phone!
  • Factory calibration for wavelength and, if required, also NIST-traceable spectral irradiance

The very narrow aperture angle of the entrance optics combined with the very high sensitivity make the OL0050-HSBS ideal for display calibration applications without the need for any additional accessories. In addition to this, we are continually expanding our range of accessories to cater to the needs of a steadily growing number of applications.

The OL0050-HSBS and the related software and accessories are ‘100% OPTO4L, Made in Germany’ products. We have the know-how and resources to implement your application in the area of optical metrology.

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