Posted in | Spectrometers

Spero® IR Microscope: Leading Mid-IR Spectroscopy Innovation

Using widely adjustable mid-infrared quantum cascade laser (QCL-IR) technology, the Spero® series of microscopes is a class apart and the world's first and best wide-field spectroscopic microscopy and imaging platform. Users can obtain high-quality data at unprecedented speeds.

Forged from Field Experience, Powered by Daylight™

The scientific community's demand for label-free, high-throughput, high-sensitivity infrared microscopy was met by the Spero® microscope. In 2014, they invented the first wide-field QCL-IR microscope to function over the crucial spectral fingerprint range (5–11 µm), building on Daylight’s experience in QCL-IR technology, systems, and equipment.

Since 2014, Daylight has worked to improve and increase the performance of the Spero platform, which is now in its third generation. Spero systems have been successfully deployed in over 12 countries and field-tested in various challenging applications, including tissue diagnostics, cancer research, and the characterization of innovative metamaterials and environmental microplastics.

QCL-IR Microscopy with Spero®

Spero-QT 340

The third-generation Spero system, the Spero-QT 340, builds on the achievements of its ground-breaking forerunners, which were introduced in 2014 and 2017, respectively. The Spero-QT 340, like its predecessors, offers unparalleled mid-IR spectroscopy and does so without the requirement for cryogenic cooling or expensive lab space. It also significantly outperforms FTIR microscopes in terms of speed, field-of-view, and spatial resolution.

Moreover, it preserves its two predecessors' high-resolution, wide-field characteristics while generating twice as much data in a tenth of the time and reaching unprecedented signal-to-noise ratios (SNR). The Spero-QT 340 stage has a larger sample container, making it more compatible with microfluidic accessories and devices. It can scan up to three microscope slides.

According to Daylight's own, patented QCL-IR light engine, Spero-QT 340 is orders of magnitude quicker than Raman and Photothermal IR microscopes. It avoids sample auto-fluorescence and sample deterioration caused by highly concentrated light sources.

Spero microscopes provide novel data collection modalities, including user-defined sparse discrete frequency data collection and live, real-time chemical imaging, thanks to a patented wide-field, low-noise instrument architecture. Spero is a suitable option for laboratories with limited space because of its compact desktop footprint (measured in centimeters here).

Spero-LT 340

The Spero-LT 340 is the latest addition to the Spero product line. The LT provides the same high-performance speed and resolution as the Spero-QT but at a reduced cost for users who simply want transmission and wide-field imaging (ideal for tissue imaging and microplastics). Spero-LT enables users to upgrade to Spero-QT later, if necessary.

Why Quantum Cascade Laser Infrared (QCL-IR) Microscopy?

Quantum cascade lasers have orders of magnitude higher spectral brightness than incoherent light sources employed in FT-IR, for example. The Spero QCL-IR microscope makes full use of this increased spectral brightness, as well as a set of patented compound refractive objective lenses, to illuminate hundreds of thousands of pixels simultaneously. This patented technique allows for extraordinarily high throughput chemical imaging without losing sensitivity.

The widely recognized and widely used Beer-Lambert absorption concept is the foundation of QCL-IR-based spectroscopy. As a result, it can be used to accurately and immediately quantify the amount of an unknown material present in addition to being able to spectrally fingerprint it.

Other methods, such as Raman and Photothermal microscopy, require a particular understanding of the sample material attributes (e.g., scattering efficiency, thermal diffusion, etc.) to provide a quantitative estimate. To accomplish spectral fingerprinting using single point raster scanning IR reflectance equipment, the real and imaginary components of the sample’s refractive index must be separated.

What is the Difference Between QCL-IR Microscopy and FT-IR Microscopy?

Since the late 1960s, Fourier Transform Infrared, or FT-IR, has been widely employed for spectroscopy and microscopy applications. With increasing throughput demands from imaging applications, other technologies have started to replace FT-IR.

The most significant difference between QCL-IR and FT-IR is in signal-to-noise ratio (SNR) and time-to-results. FT-IR is often used with incoherent light (such as Globar®), which is similar to an incandescent lightbulb.

This light produces photons throughout a wide spectral range and is detected with a scanning interferometer. Since the light source is thermal, high sensitivity detectors and liquid nitrogen are required.

Alternatively, QCL-IR microscopy employs all photons at about the same wavelength, significantly increasing spectral irradiance.

This enables the user to capture a chemical image using an uncooled focal plane array detector (FPA) 150 times quicker than a standard FT-IR microscope with equal SNR. While FT-IR has a broader spectrum, the success of QCL-IR in several applications has demonstrated that this additional coverage is not required for many applications.

How Does QCL-IR Microscopy Work?

A QCL-IR microscope consists of four major subsystems:

  1. A tunable quantum cascade laser or a string of QCLs operating together to span larger spectral ranges. 
  2. A set of wide-field imaging objective lenses
  3. An infrared-sensitive focal plane array imager
  4. A precision X, Y, and Z stage

The single wavelength (wavenumber) band that emanates from the QCL at any one time is narrow. The diffraction grating, an external cavity frequency selective element, is exactly regulated by the instrument at a fast tuning speed (msec) to produce the desired laser wavelength. This process is conducted seamlessly.

Following transmission (in the case of transmission imaging) through the sample, the laser light is then captured by the focal plane array imager after passing through a wide-field infrared objective. A unique, broadband, uncooled microbolometer camera running at video frame rates is the Spero microscope's imager.

Wide-field imaging provides a far larger field-of-view (FOV) than FT-IR, allowing for live, single-frequency, and quick hyperspectral imaging of materials.

Spero® IR Microscope: Leading Mid-IR Spectroscopy Innovation

Image Credit: DRS Daylight Solutions Inc.

Lasers and Coherence

Coherence is a fundamental and crucial quality of laser light, divided into two categories: temporal (frequency) and spatial.

Daylight has optimized the Spero’s overall performance and met the needs of key applications like tissue imaging and particle analysis by leveraging its almost two decades of expertise in designing and producing thousands of QCL-IR sources and instruments.

Under the hood, Daylight’s most cutting-edge and exclusive coherence control technology is utilized by the Spero platform to suppress spatial and temporal coherence effects resulting from light-sample interaction, while maintaining the two main intrinsic benefits of the laser source: high spectral brightness and a clearly defined linear polarization state.

In light-starved applications like flowing liquid analysis or reflectance studies on weekly reflecting samples, maintaining optical power is crucial to optimizing signal. When doing polarization dependent spectroscopic research on new materials, maintaining the polarization state is extremely important.

The visible (left) and infrared (right) images of a 50 Euro note taken by the Spero-QT 340 microscope below demonstrate how this technology generates high-quality images without the need for any digital post-processing. These raw (unprocessed) images do not contain coherence artifacts.

Visible (Left) vs QCL-IR (Right) reflection mosaic image of a 50 Euro note.

Visible (Left) vs QCL-IR (Right) reflection mosaic image of a 50 Euro note. Image Credit: DRS Daylight Solutions Inc.

ChemVision™ Software for Spero

Spero systems provides ChemVision™ software as part of a comprehensive imaging solution. ChemVision allows users to examine samples at a single frequency in real-time or acquire entire hyperspectral data cubes in under a minute. Data can be exported in MATLAB or ENVI format for additional processing.

Chemometrics packages are available. Daylight collaborated with Epina ImageLab to provide a flexible and open programming interface for improved data processing and image analysis.


Features and Benefits

  • Offers several configuration choices, including expanded wavelength coverage and automated polarization control
  • No cryogenic cooling needed
  • Quick setup means more time for analysis
  • Transmission, visible and reflection modes
  • Diffraction-limited, high-sensitivity imaging with Focal Plane Array (FPA) detector
  • Multiple, high-NA, large FOV imaging optics (0.7 NA and 0.3 NA)
  • Live, real-time infrared imaging
  • Ultra-high brightness QCL technology enables high-throughput hyperspectral imaging (>7 M spectral points per second)
  • Large, flexible sample compartment


  • Real-time reaction monitoring
  • Materials testing and analysis
  • Forensics
  • Chemical detection and identification
  • Microplastic Research
  • Biomedical imaging of tissues, cells, and fluids
  • Cancer research
  • Pharmaceutical testing of tablets, powders, and liquids
  • Drug discovery: API and excipient optimization and down-selection
  • Protein secondary structure and aggregation testing

Accessories and Configuration Options

  • Expanded Wavelength: Add extended wavelength coverage to 1900–950 cm–1
  • Polarization: Add rotation stage to take polarized images
  • Blue Shifted – Add blue shifted range to 2225–2000 cm–1 and 1800–1200 cm–1

Product Specifications

Source: DRS Daylight Solutions Inc.

. . .
Specifications  IR Imaging Mode
Wavelength Range Spero-LT Standard Configuration: 1750 cm-1 to 1000 cm-1
Spero-QT Standard Configuration: 1800 cm-1 to 950 cm-1
Customizable between 2300 cm-1 and 800 cm-1
Image Cube Acquisition Time < 40 s (450 absorbance images collected at 2 cm-1 spacing)
Camera Array Size  480 × 480 480 × 480
Image Pixel Size 1.3 µm (0.7 NA) 4.3 µm (0.3 NA)
Diffraction-Limited Spatial Resolution < 5 µm @ λ = 5.5 µm < 12 µm @ λ = 5.5 µm
Numerical Aperture  0.7 0.3
Spectral Resolution  Variable, down to 2 cm-1
Minimum Detectable Signal < 3 mAU per scan
Working Distance  > 8 mm > 25 mm
Field of View (FOV) 650 × 650 µm (0.7 NA) 2 mm x 2 mm (0.3 NA)


Microplastic Analysis with QCL-IR Microscope

Microplastic Analysis with QCL-IR Microscopy. Video Credit: Daylight Solutions Inc.

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