A new comparative study shows that scientific CMOS (sCMOS) cameras could rival traditional CCD detectors in certain Raman CARS spectroscopy applications, offering faster readout and dynamic range despite slightly higher noise levels.
CCD vs. sCMOS: A New Chapter in Spectroscopic Detection
In the field of Raman spectroscopy, charge-coupled device (CCD) cameras, especially electron-multiplied (EM-CCD) variants, have long been the gold standard for capturing weak signals. But a new international research collaboration has revealed that scientific CMOS (sCMOS) detectors may now offer a competitive, and in some cases superior, alternative (1).
The study, published in the Journal of Raman Spectroscopy, was conducted by W. J. Niels Klement and Philippe Leproux of the Xlim Research Institute at the University of Limoges (France), Wesley R. Browne of the University of Groningen (Netherlands), and Hideaki Kano of Keio University (Japan). Their work compared EM-CCD and sCMOS camera performance in both spontaneous Raman and multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopy (1).
Laser beam passing through a prism, splitting into a spectrum of colors © Waqasiii_Arts -chronicles-stock.adobe.com
A New Challenger Emerges
EM-CCDs are renowned for low noise, high sensitivity, and effectiveness in detecting weak signals in low-light scenarios. However, EM-CCDs are hampered by slow readout times and artifacts like blooming and smearing when exposed to intense light. These limitations can hinder performance in bright-light techniques such as multiplex CARS, where fast and high-dynamic-range detection is essential (1).
In contrast, sCMOS sensors offer faster readout, larger dynamic range, and immunity to readout artifacts—thanks to parallel pixel architecture. Unlike CCDs, which transfer charge through a column of pixels during readout, sCMOS detectors read out each pixel independently. This key difference allows sCMOS cameras to avoid blooming and smearing, enabling cleaner imaging even when weak signals are adjacent to strong ones (1).
Side-by-Side Spectral Testing
Using a custom-built broadband CARS microscope and polystyrene bead reference samples, the researchers compared both detector types under identical conditions. The EM-CCD (Newton DU970P-FI) and sCMOS (Zyla 4.2) cameras were installed on a Kymera 193 spectrograph with a switchable mirror system to alternate between them without altering the optical path. Similar comparisons were also conducted for spontaneous Raman spectra using cyclohexane as a reference (1).
While EM-CCDs maintained superior sensitivity at low light and faster exposure accumulation (for example, 100 × 5 ms frames), sCMOS detectors demonstrated faster readout and handled high-intensity spectra more cleanly. Notably, the sCMOS’s dynamic range and independence from blooming enabled it to detect subtle features—such as Raman overtones—more effectively when close to intense bands (1).
The EM-CCD’s larger pixel size (16 µm) allowed for higher per-pixel photon collection, while the sCMOS’s higher pixel density (2048 × 2048 at 6.5 µm) meant more spatial data but required stitching of spectral ranges due to reduced total sensor width. Even with lower quantum efficiency (QE) in the near-infrared (NIR), sCMOS still performed well in CARS applications, especially when avoiding fringing that can affect NIR-enhanced CCDs (1).
Implications for the Future of Spectroscopy
Despite their current sensitivity advantage, EM-CCD detectors may be approaching their technological ceiling in terms of readout speed. As sCMOS technology continues to improve in noise reduction and QE, the study suggests these cameras could become preferred tools in bright-light and rapid-acquisition spectroscopy techniques, including spectral imaging and time-resolved studies (1).
“The performances of the two detector types are not substantially different at readout rates above 20–50 Hz,” the authors noted. “We anticipate that sCMOS-based cameras will find application for bright spectroscopies, such as multiplex CARS, as well as spontaneous Raman spectroscopy and Raman spectral imaging” (1).
This work paves the way for broader adoption of sCMOS detectors in analytical spectroscopy, offering an alternative that is faster, artifact-free, and more cost-effective for many real-world applications of CARS (1–3).
References
(1) Klement, W. N.; Leproux, P.; Browne, W. R.; Kano, H. CMOS and CCD Detection in Raman Spectroscopy: A Comparison Using Spontaneous and Multiplex Coherent Anti‐Stokes Raman Scattering (CARS). J. Raman Spectrosc. 2025, n/a, e6773. DOI: 10.1002/jrs.6773
(2) Agarwal, U. P. Analysis of Cellulose and Lignocellulose Materials by Raman Spectroscopy: A Review of the Current Status. Molecules 2019, 24 (9), 1659. DOI: 10.3390/molecules24091659
(3) Inoue, K.; Okuno, M. Coherent Anti-Stokes Hyper-Raman Spectroscopy. Nat. Commun. 2025, 16, 306. DOI: 10.1038/s41467-024-55507-0
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