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How to maximize gas detection performance by using the multi-gas sensing VAPIR™ lenses


Infrared (IR) imaging technologies first arrived in the 1940s as a part of military research into early night vision and detection capabilities. As the science of detector materials advanced, the available devices were eventually released to the civilian market under a “dual­­–use technology” status.[1] This expansion in the application of infrared sensing led to the discovery of thermal IR imaging via heat mapping which could “see” gasses that, otherwise, would have stayed invisible to the human eye. Thus, Optical Gas Imaging (OGI) was born. Today, gas sensing solutions have reached revolutionary heights, with a few examples including quantum sensing, tunable diode laser absorption spectroscopy (TDLAS) and quartz-enhanced photoacoustic spectroscopy (QEPAS). However, in this innovative mix, OGI technology has remained just as relevant next to the other emerging approaches by serving those that need accurate visual representations of leaks and a fast method to locate them.

A chain is only as strong as its weakest link, and as IR focal plane arrays (FPAs) have matured as a technology, their companion optical lenses must also equally evolve. The lenses used for gas visualization represent a cornerstone piece of instrumentation. If their features are not matched to the required application and respective FPA, accuracy failures are guaranteed to occur.

With the emergence of gas-sensing “mid wave” infrared (MWIR) cameras using IR FPAs, G&H also started producing compatible MWIR lens systems, initially for propane gas leaks. Propane emits thermal radiation at the very particular wavelength of around 3.3µm. In response to the particular request, the engineering teams at Gooch & Housego designed a lens specially for imaging around this wavelength. This allowed the customer to directly observe the size, nature and location of propane gas leaks with their specialized MWIR camera. Since then, we have invested 10+ years of consistent research and development in fine-tuning what would eventually become known as the VAPIR Series™, a commercial narrowband MWIR gas-sensing lens assembly with enhanced sensitivity and high customization capability.

Optical Gas Detection (OGI)

1. High-degree of lens sensitivity

The most important decision-making factor for MWIR lenses lies in their level of detection sensitivity. For OGI, gas detection, recognition, and identification rank high among the necessary functionalities for a thermal imaging camera. High sensitivity is critical to detecting small leaks and leaks with a faint thermal signature before they become worse. The VAPIR Series™ is designed with this in mind. The low F/# of the lenses gives them a large aperture relative to their focal lengths and the high-efficiency anti-reflective (AR) coating reduces Fresnel reflections from the lens materials. These features are combined to maximize the VAPIR™ series’ sensitivity.

2. Made for wide-field imaging, capable of small detail detection

Smaller fugitive gas leaks will become the main focus of the detection process in the future, as the available technology offers more precise locating capabilities within a faster timeframe. To accomplish this, OGI lenses must fulfill two specific design criteria. Firstly, lenses must be capable of imaging a sufficiently wide field of view (FOV), allowing them to monitor as much of a scene as is possible. Second, they must have a high resolution to preserve enough detail for gas detection and identification when looking at a smaller region of interest (ROI) in the image. The VAPIR™ series of lenses offers multiple shorter focal length options and are easily customizable to the specific needs of the given situation. All VAPIR™ lenses offer a high degree of resolution to preserve the detail needed for accurate identification.

3. Proximity

The distance at which the gas detection occurs influences the vapor identification process. This point represents the biggest difference between MWIR and LWIR thermal cameras in terms of their usage. In certain conditions LWIR thermal cameras are subject to much more “noise” in their image, which makes identifying the gas image “signal” more difficult. Both manual and motorized configurations using MWIR lens systems can cover this hindrance.

4. Taking care of product accessibility

Vertical integration is becoming an ever-growing interest for OGI camera manufacturers because of potential product availability issues. Currently, certain market shifts[2] around access to materials have generated a level of instability regarding reliability. Especially when thinking of product delivery, such a concern plays an important role in manufacturer choice. As the VAPIR series™ are a 100% “Made in the USA” solution, using a special combination of heritage IR glass elements, G&H has proactively tackled the issue of potential disruptions in the manufacturing cycle. At the same time, since we supervise all aspects of design and production for our solutions, the quality of delivered lenses is guaranteed and comes at a more cost-effective rate.

5. Tailoring the lens system to every need

The flagship trait of G&H as a business is our capacity for adaptable and swift delivery of outstandingly fitting products to our clients. Considering the wide scope of applicability for our MWIR lens systems, ranging from the oil and gas industry to aerospace and defence, healthcare, HVAR and others, each solution design requires careful customization on our part. Although critical to final performance, this aspect of the production cycle is often underrated by OGI businesses. G&H is equipped, both technologically and procedure-wise, to cater to the different demands when it comes to lens manufacturing for gas detection.

6. Contributing to a culture of safety

Risk mitigation through accurate gas detection is also affecting the overall organizational matrix, especially in high-risk industries. As mentioned by Health and Safety International, “A culture of safety built upon proper gas detection leads to increased employee trust, proactive responses to emergencies, and continuous improvement in safety protocols. Implementing a comprehensive gas detection strategy requires careful planning, technology selection, and ongoing maintenance.”[3] From trace levels of gas to higher concentrations, the ability to visualize leaks properly maximizes safety via preventive application. As such, the magnitude of incorporating MWIR multi-lens systems such as VAPIR™ upgrades the scope of the practice from a simple identification procedure to a vital health and safety measure.

From an engineering viewpoint, every problem drives a solution. Even more, through intelligent blueprinting and reliable design, this solution can become a state-of-the-art piece of technology that defines the quality standards in its particular field. This precise mindset has been employed in the development and upgrading of the VAPIR series™. The performance confirmation of our solutions can be traced back to the time and application maturity of the VAPIR™ lenses, being for the past 10+ years in continuous production. We look forward to contributing to the safety, profitability and performance of your business with our high-precision MWIR product line.

Highlights of VAPIR™ MWIR lens series:

  • Made in the USA.
  • Lightweight, sensitive, with versatile applicability.
  • Wavelength: 3.2–3.7 µm.
  • Aperture: f/1.5.
  • Focal length: 25 mm, 50 mm, 100 mm.
  • Image Diameter: 12.3 mm, 20 mm.
  • Detected gases:
  • Industries: oil and gas, petrochemical, chemical, HVAR, semiconductor manufacturing, emission monitoring, healthcare, aerospace and defence.


1 Rogalski, A. (2012). History of Infrared Detectors. Opto-Electronics Review, 20(3).

2 One example relevant for today’s manufacturing markets can be found in the current material restriction scenario coming from China: Marsh, A. L. & N. (2023, August 1). Gallium and germanium: What China’s new move in Microchip War means for World. BBC News.

3 October 2023, T. L. S. G. 20. (2023, October 20). Enhancing industrial safety culture through effective gas detection.

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