How to choose a spectrometer
Choosing the right spectrometer for a given application is not always straightforward. Many parameters—wavelength range, resolution, sensitivity, speed, robustness, and overall optical design—interact in ways that are not immediately obvious. A change in one design choice can influence several performance characteristics at once, affecting cost, size, stability, and measurement quality. This guide explains how these parameters relate, why they matter, and how to navigate the trade‑offs so you can select a spectrometer architecture that truly fits your application rather than one that only appears suitable on paper.
Key parameters when selecting a spectrometer
The basic parameters you need to know before choosing a suitable spectrometer are:
- Wavelength range
- Resolution
For instance, if you need to analyze color you need a spectrometer that covers the visible spectrum from approximately 400 nm to 750 nm.
The resolution is the spectrometer’s ability to distinguish between two closely spaced wavelengths. So, if your spectrum has some sharp peaks that are separated by say 0.5 nm or more, you must choose a spectrometer with at least 0.5 nm resolution.
Some applications (like Raman and IR spectroscopy) will not list the wavelength range and resolution in nanometer (nm) directly but rather in terms of inverse cm (cm-1). For Raman you can use our RamanShift calculator to convert back and forth between nm and cm-1.
Even though you know your wavelength range and resolution there are still a lot of possible spectrometer design options. So your final choice of spectrometer will depend on the importance of parameters such as overall size, cost, speed, sensitivity, signal-to-noise ratio, dynamic range, linearity, thermal stability, and robustness. Below, you can find some general guidelines that may help you determine what kind of spectrometer parameters you should focus on for you application.
Get help from our experts
At Ibsen, we have decades of experience guiding instrument manufacturers in selecting the right OEM spectrometer for their specific application. Our team works closely with you to understand your performance requirements, environmental constraints, and integration needs, ensuring that the spectrometer you choose is the best fit for your instrument design. You are always welcome to contact us to discuss your spectroscopy project and explore how our OEM platforms can support your development.
Spectrometer characteristics
No spectrometer can excel in every parameter simultaneously, and choosing the right design always involves compromise. By focusing on the two or three characteristics that truly define your application, you can make informed decisions about the architecture. Below is an overview of the most important parameters to consider.
Small spectrometer
If you need a compact spectrometer for integration into a space-constrained or handheld instrument, you should generally aim for:
- High grating dispersion (many lines per mm in the grating)
- Small detector size (few pixels and narrow pixel pitch)
- Low numerical aperture/high f-number
Low-cost spectrometer
If cost is one of your primary concerns, consider the following general guidelines:
- Choose a small spectrometer, as compact designs typically reduce component count and size and thereby overall cost.
- Use a low‑end, non‑cooled CCD/CMOS detector or a photodiode array, which are more affordable than high‑performance, cooled sensors.
- Select a low‑resolution spectrometer, since higher resolution typically lead to more expensive spectrometers.
High-speed spectrometer
If your instrument needs to read many spectra per second, you should in general aim for:
- High through-put spectrometers with
- Transmission grating based design
- High NA / Low f-number
- Few optical elements (preferably lenses)
- High-speed, non-cooled cameras
Highly sensitive spectrometer
If you have very little light from your sample you need a highly sensitive spectrometer and you should in general aim for:
- High throughput spectrometers
- Transmission grating based
- High NA / Low f-number
- Few optical elements (preferably lenses)
- A wide and tall input slit
- Cooled camera/detector that enable long integration time
- Highly sensitive CCD (or CMOS) detector with tall pixels
Spectrometer with high SNR
If signal levels have to be very stable over time you have several options depending on the actual signal level and balance of cost versus performance:
If your signal level is very weak and tends to drown in the noise:
- High throughput spectrometers
- Transmission grating based
- High NA / Low f-number
- Few optical elements (preferably lenses)
- A wide and tall input slit
- Cooled CCD/CMOS detectors with tall pixels that allow long integration time with low noise
If your signal level is very weak but, you also need a low cost solution:
- High through-put spectrometers
- Transmission grating based
- High NA / Low f-number
- Few optical elements (preferably lenses)
- Non-cooled CCD/CMOS detectors where you average over many short integration periods
If your signal level is stronger but you need to distinguish small signal variations:
- High through-put spectrometers
- CMOS/NMOS detectors with very low noise
Spectrometer with large dynamic range
If there are large (several orders of magnitude) variations in your signal levels you should in general go for:
- Low stray-light spectrometers
- Holographic, Master gratings rather than replicated, ruled gratings
- As few optical surfaces as possible
- Bandpass filters to block un-wanted light
- CMOS/NMOS detectors with very large well depth or non-cooled CCD/CMOS detectors where you average over many short integration periods.
Linearity
If you require a linear relation between signal level and integration time you should in general go for:
- NMOS/BT-CCD detectors with very good linearity or
- CCD/CMOS detectors where you make a software correction for linearity.
Athermal spectrometer
If your spectrometer should operate under varying temperature conditions you should in general go for:
- Spectrometers with low wavelength and power shift vs. temperature
- Lens-based, telecentric rather than mirror-based spectrometers
- All-dielectric, transmission grating based rather than reflection grating based spectrometers
- Thermally stable mounting methods
- Short integration time or temperature controlled detectors if you need longer integration time
Robust spectrometer
If your spectrometer should operate under demanding environmental conditions you should consider some of the following:
- Spectrometers with low wavelength and power shift vs. external impacts
- Lens-based, tele-centric rather than mirror-based spectrometers
- Transmission grating based rather than reflection grating based
- Environmentally qualified mounting methods for optics and gratings
- Short integration time and/or temperature controlled detectors if you need longer integration time
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