Spero® IR Microscope: Mid-IR Spectroscopy Solutions

The first and best wide-field spectroscopic microscopy and imaging platform in the world, the Spero^® series of microscopes is a class apart. Based on broadly tunable mid-infrared quantum cascade laser (QCL-IR) technology, they offer unmatched speeds and receive the highest-caliber data.

Forged from Field Experience, Powered by Daylight™

The Spero® microscope addresses the scientific community's need for high-throughput, high-sensitivity, label-free infrared microscopy.In 2014, Daylight expanded upon its proficiency in QCL-IR technology, systems, and equipment by creating the first wide-field QCL-IR microscope capable of functioning in the crucial spectral fingerprint range (5–11 µm).

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 new Spero-QT 340 system is the third-generation Spero, building on the success of its trailblazing predecessors, which debuted in 2014 and 2017, respectively. Like its predecessors, the Spero-QT 340 offers unsurpassed mid-IR spectroscopy, significantly surpassing FTIR microscopes in spatial resolution, speed, and field-of-view while removing the requirement for cryogenic cooling and costly lab space.

Furthermore, it retains its two predecessors' wide-field, high-resolution characteristics, but it also can generate twice the data in one-tenth of the time and achieve exceptional signal-to-noise ratios (SNR). The Spero-QT 340 stage can scan up to three microscope slides and has a bigger sample compartment, making it more compatible with microfluidic devices and accessories.

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

Spero-LT 340

The Spero-LT 340 is the most recent addition to the Spero product lineup. The LT provides the same high-performance speed and resolution as the Spero-QT, but at a reducedcost to those who simply want transmission, wide-field imaging (ideal for tissue imaging and microplastics). Spero-LT permits usersto upgrade to Spero-QT if necessary.

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

Quantum cascade lasers have orders of magnitude higher spectralbrightness than incoherent light sources employed in FT-IR. 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 exceptionally high throughput chemical imaging without losing sensitivity.

QCL-IR spectroscopy is based on the well-acknowledged Beer-Lambert absorption concept. It is therefore a technique for spectrally fingerprinting unknown substances and directly quantifying how much substance is present with great precision.

Other methods, such as Raman and Photothermal microscopy, require specific knowledge of the sample material's characteristics (e.g., scattering efficiency, thermal diffusion, etc.) to provide a quantitative estimate.

Single point raster scanning IR reflectance instruments require the decoupling of the sample’s real and imaginary refractive indexes to accomplish spectral fingerprinting. This post-processing can be heavily impacted by particle form and size, making it challenging to use existing spectral libraries.

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

FT-IR (Fourier Transform Infrared) has been widely employed in microscopy and spectroscopy since the late 1960s. As imaging applications require higher throughput, new technologies are displacing 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 quite 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, resulting in significantly increased spectralirradiance. This enables the user to capture a chemical image using an uncooled focal plane array detector (FPA) 150 times quicker than a traditional 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; and (4) a precision X,Y,Z stage. At any one time, the QCL emits just one short wavelength (wavenumber) band.

The exact wavelength of the laser is accurately regulated by activating an external cavity frequency selective element (a diffraction grating), which the device does flawlessly at a quick tuning speed (msec). In transmission imaging, the laser light is transmitted through the sample before passing through a wide-field infrared objective and being collected by the focal plane array imager.

The Spero microscope’s imager is a specialized, broadband, uncooled microbolometer camera that operates at video frame rates. 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.

Image Credit: DRS Daylight Solutions Inc.

Lasers and Coherence

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

Daylight has leveraged over two decades of expertise in building and producing thousands of QCL-IR sources and instruments to improve the Spero's overall performance and fulfill the needs of crucial applications, such as tissue imaging and particle analysis.

Under the hood, the Spero platform employs some of Daylight’s most advanced and proprietary coherence control technology to suppress both spatial and temporal coherence effects caused by light-sample interaction while retaining the laser source's two main intrinsic advantages: high spectral brightness and a well-defined linear polarization state.

Maintaining optical power is crucial for optimizing signalsin light-deprived applications, such as weekly reflecting sample reflectance studies or flowing liquid analysis. Polarization-dependent spectroscopy research on new materials requires special attention to maintaining the polarization state.

As seen by the accompanying visible (left) and infrared (right) images of a 50 Euro note taken by the Spero-QT 340 microscope, this technique generates high-quality images without needing any digital post-processing. These unprocessed or raw images do not contain coherence artifacts.

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 provide 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, open programming interface for improved data processing and image analysis.

Highlights

Features andBenefits

Large, flexible sample compartment

Multiple configuration options, including extended 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

High-throughput hyperspectral imaging enabled by ultra-high brightness QCL technology (>7 M spectral points per second)

Applications

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

Real-time reaction monitoring

Accessories & Configuration Options

Polarization – Add rotation stage to take polarized images

Blue Shifted – Add blue shifted range to 2225-2000 cm^-1 and 1800-1200 cm^-1

Extended Wavelength – Add extended wavelength coverage to 1900-950 cm^-1

Product Specifications

Source: DRS Daylight Solutions Inc.

Microplastic Analysis with QCL-IR MicroscopePlay

Microplastic Analysis with QCL-IR Microscopy. VideoCredit: DRS Daylight Solutions Inc.