MKS-Ophir’s advanced SWIR, MWIR, and LWIR zoom lenses deliver exceptional long-range DRI capabilities, compact SWaP optimization, and compatibility with the latest small-pixel, large-format IR detectors.
Infrared (IR) imaging technology plays a crucial role in modern security and surveillance systems, enabling the detection, recognition, and identification (DRI) of objects in various environments.
These functions are vital across a range of applications, including intelligence, surveillance, reconnaissance (ISR), targeting, border security, and counter-drone operations.
While IR imaging has existed for decades, its significance—and the complexity of its deployment—has only grown with advancements in sensor technology, increasingly sophisticated threats, and emerging market trends. As a result, IR cameras equipped with high-performance zoom lenses are now more important than ever for capturing clear imagery of people, vehicles, drones, and other distant targets.
This article examines the challenges of designing and manufacturing high-performance IR zoom lenses for DRI applications. It reviews innovative solutions developed by MKS-Ophir to meet these challenges, as well as an overview of long-range product options in SWIR, MWIR, and LWIR to illustrate the current state-of-the-art in IR technology.
Products in the SWIR, MWIR, and LWIR spectral ranges coexist because each offers distinct advantages. SWIR is optimal for long-range daytime observation, while MWIR excels in long-range surveillance day and night.
Both MWIR and SWIR function well in adverse conditions, such as smoke, dust, heavy haze, and high humidity. LWIR, on the other hand, is the preferred spectral range for observing burning targets and against sun glints.
Key Requirements and Trends in DRI
DRI applications require highly specialized imaging systems to meet stringent requiremen
ts and perform optimally under a wide range of challenging conditions. However, the performance demands for DRI are constantly evolving due to several external factors.
Sensor Improvements
Continuous technological advancements are producing sensors with smaller pixel pitches and higher pixel counts, thereby increasing camera resolution. As a result, IR imager designers must avoid “optics-limited” scenarios, where imaging system performance is constrained by the optics rather than the sensor.
Today, sensors with a 10 μm pixel pitch are common, and even smaller sizes (8 μm, 7.5 μm, or 5 μm) are becoming more prevalent. The SXGA sensor format (1280 x 1024 pixels) is standard, with some systems incorporating full HD format (1920 x 1080 pixels) sensors.
SWaP-C Optimization
Size, weight, power, and cost (SWaP-C) optimization is a primary focus in military system design, influencing the development of advanced technologies across platforms. Unmanned aerial vehicles (UAVs) and drones used in DRI applications require optical systems that are lightweight, compact, and energy-efficient without sacrificing performance.
Multi-Spectral Operation
Modern surveillance systems frequently utilize multispectral imaging, operating over multiple spectral bands (visible, SWIR, MWIR, and LWIR) to perform effective surveillance under various lighting and weather conditions. This enhances situational awareness and improves the ability to detect, identify, and recognize elements and threats within a scene.
Environmental and Operational Challenges
Security and surveillance operations often take place in adverse environments, such as extreme temperatures, rain, fog, dust, and saltwater exposure.
Day-and-night operations are common, and imagers may experience shock, vibration, and require periodic cleaning. Lens designs must endure these operational challenges without compromising performance.
Table 1: Performance Comparison: SWIR vs MWIR vs LWIR
MKS Ophir Solutions
Meeting the requirements for modern security and surveillance operations necessitates a specialized approach in both design and manufacturing. MKS-Ophir employs various methods to meet the high demands for DRI and SWaP-C performance.
DRI Resolution Requirements
Ophir’s advanced design capabilities address the stringent resolution and optical performance standards for DRI lenses. The design process leverages extensive experience and advanced optical design software to create innovative solutions.
Ophir’s designers have access to a comprehensive set of materials, surface shapes, and surface types, allowing the use of spheres, aspheric elements, freeforms, and even diffractive or holographic elements to achieve high MTF targets and minimize chromatic aberrations.
The production capabilities at Ophir are key to realizing the full potential of these designs. High-precision fabrication techniques allow for accurate optical surface production and precise component alignment. The use of large diameter optics, for example, is advantageous for achieving high magnification in DRI zoom lenses.
Additionally, integrating design and manufacturing within a single facility enables Ophir to implement design for manufacturing (DFM) principles, facilitating continuous improvement and performance optimization.
SWaP-C Optimization
Using advanced IR materials enables Ophir to reduce lens element count, minimizing system size, weight, and production costs. Aspheric and diffractive elements help to minimize aberrations and reduce components, which is essential for compact continuous zoom lens designs. Ophir’s SWaP-C capabilities are further extended by employing folded-optics configurations and multi-spectral designs.
Environmental Stability and Durability
Ophir lenses are often constructed with materials like titanium and magnesium alloys, selected for their strength, low weight, and corrosion resistance. Athermalization techniques enable these lenses to maintain focus across a broad temperature range.
Combining materials with differing thermal expansion coefficients enables the creation of assemblies that inherently compensate for thermal changes. Lenses that remain stable and accurate in varying environmental conditions reduce the need for frequent recalibration, enhancing the operational efficiency of surveillance systems.
Hard carbon (HC / DLC) and high-durability (HD) coatings are applied to optical surfaces for resistance to abrasion and environmental degradation. Ophir lenses also meet or exceed IP67 environmental standards, ensuring reliable performance in rain, dust, and extreme conditions.
Production Capabilities
Ophir offers a wide range of IR optics for security and surveillance applications, including:
- SWIR lenses
- MWIR lenses for cooled cameras
- LWIR lenses for uncooled cameras
- Lightweight IR zoom lenses
- Long-range IR zoom lenses
Product Snapshot
Ophir manufactures over one hundred IR zoom lenses, including more than a dozen specifically designed for DRI applications. Below are examples of products that highlight Ophir’s achievements in optimizing performance, weight, and size.
SWIR & NIR 25-250mm f/5.5 (NFOV) / f/4.0 (WFOV)
The SWIR & NIR 25-250mm f/5.5 lens combines an extensive detection range with effective operation across varying conditions, including both day and night. Its capability to penetrate haze, smoke, and maritime fog enhances operational utility.
Designed to work with the latest 5 μm SXGA SWIR detectors, along with 10 μm SXGA and 15 μm VGA sensors, this lens represents a significant advancement in SWIR technology.
Notably, the lens is optimized for SWaP, achieving a weight of 0.86 kg and a length of 214 mm—about 60% lighter than comparable SWIR lenses. Additionally, chromatic correction extends usability down to 0.7 μm with minimal distortion.
Key Benefits
- Compatible with 12 μm pixel 1280×1024 SXGA uncooled LWIR cameras
- Passive athermalization for stable performance in various conditions
- Vehicle detection range exceeding 12.5 km
- High-durability, low-reflection hard-carbon AR coatings
Performance Analysis
Figures 1(a) and 1(b) illustrate the Modulation Transfer Function (MTF) performance for wide-field (WFOV) and narrow-field (NFOV) zoom positions.
These graphs showcase Sagittal (S) and Tangential (T) MTF components across spatial frequencies at different field positions for the SXGA 10 μm detector. The MTF holds at high values across the entire zoom range, especially in narrow FOV (NFOV) positions, where fine detail is crucial.
For the 5 μm sensor, the MTF, particularly at narrow and medium FOV positions, approaches the diffraction limit, outperforming the 10 μm sensor.
This results from the 5 μm sensor’s reduced maximum off-axis field (half of that of the 10 μm) while doubling the cycle/mm from 50 to 100. Sagittal MTF remains close to the diffraction limit across the focal plane, though Tangential MTF is somewhat lower, especially in WFOV.
SupIR® (MWIR) 60-1200 mm f/4.0
The SupIR® MWIR lens excels in nighttime detection and delivers robust performance in challenging environmental conditions, including smoke, haze, and high humidity.
Offering a detection range exceeding 28 km for vehicles, it supports long-range surveillance and counter-unmanned aerial systems (C-UAS) applications.
This lens is compatible with 10 μm pixel, 1280×1024 SXGA format cooled MWIR cameras and maintains accurate line-of-sight and focus throughout the zoom range.
Key Benefits
- Compatible with 10 μm SXGA/HD detectors
- Continuous zoom with extended range
- Withstands severe shock and vibration
- Automatic focus compensation across temperature and zoom range
Performance Analysis
As shown in Figure 2, MTF performance for this lens approaches the diffraction limit across the focal plane, especially in WFOV. This high MTF level indicates a sharp, high-resolution image quality throughout the zoom range.
SupIR (LWIR) 40-300 mm f/1.5
This LWIR lens leverages thermal radiation, naturally emitted by objects, allowing detection without any external light source. It performs in complete darkness and provides reduced susceptibility to glint in daylight.
Further, the LWIR lens operates effectively in adverse weather conditions. With a 7.5X zoom ratio, it offers a broad FOV, facilitating easy target acquisition and tracking.
The lens maintains sharp focus across its zoom range and provides a vehicle detection range exceeding 12.5 km.
The lens is compatible with both 12 μm and 17 μm pixel pitch 1280×1024 SXGA format uncooled LWIR cameras, offering versatility for integration with various camera systems.
Key Benefits
- Compatible with 12 μm pixel 1280×1024 SXGA uncooled LWIR cameras
- Passive athermalization for reliable performance across conditions
- Vehicle detection range exceeding 12.5 km
- High-durability, low-reflection hard-carbon AR coatings
Performance Analysis
Figure 3(a) illustrates MTF at WFOV (40mm) and Figure 3(b) at NFOV (300mm EFL). MTF performance remains high across the focal plane, particularly in WFOV, where off-axis MTF values are near on-axis values, ensuring consistent image quality.
By integrating innovative optical designs, high-grade materials, and precise manufacturing, these lenses offer high-performance, durability, and adaptability for modern security and surveillance applications.
This range of high-performance lenses meets the rigorous demands of today’s operational environments, ensuring superior imaging across diverse and challenging conditions.
