LWIR Lenses

Posted by Ningliu on May 13th, 2017

LWIR lens

LWIR lens plays a critical role in thermal imaging surveillance applications, beyond night vision capabiliity, critical targets differentiation in poor vision conditions is considered the most practical atrribute in homeland security and defence market segamentation.

Compared to cooled system, which focal plane array detector kept at -70℃ needs cooling support, uncooled cameras are much more affordable. Aside superior sensitivity of colled system, uncooled system are dominating the market for surveillance and automonile segamentation due to its cost.

LWIR solution

On the other hand, in short distance surveillance applications, uncooled system are the best choice, but the cameras have to be equipped with objectives that have larger focal length to maintain resolution. Meanwhile, the F number will increase due to the same entrance aperture, which will dramatically reduce the amount of light for detection. In return, the uncooled system becomes insensitive. Thus, the cost is driven by increasing the aperture (larger lens), eventually drives uncooled LWIR solution more expensive than cooled version.

Germanium is frequently used for LWIR lenses as its high refractive index in LWIR wave band; However, Germanium has large thermal drift which cause expected defocus with temperature change. Hyperion Optics provides sophisticated design that balance defocus and secure stable performance in consideration of defocusing attributes of the lens, by using ZnSe (8 times better thermal defocusing compare to Germanium)

In LWIR design, Hyperion Optics optical designers also conduct thorough calculation of what happens to the housing with the impact of thermal expansion. Aluminium is frequently used as housing, for example a 20mm long aluminium housing will increase by 28 microns if the temperature increases for 60℃, the 28 micron change can be considered the same as the LWIR system’s depth of focus.

Hyperion Optics optical design

At Hyperion Optics, we conduct both passive mechanical and passive optical solutions for the best to eliminate the thermal impact in athermalization system development. For passive mechanical solution, we develop inner and outer cell separated by spacer, geometrically precise machine the spacer with the right material to attain a thermal expansion equal and opposite to the combined effect of the lenses and rest of the housing over the whole temperature range. The spacer pushes the inner cell back to the right position to keep the lens in focus. Find out more by talking or writing to us for your current LWIR needs for our passive optical solution for your own LRIP Optics Project.

Our advantage of LWIR lens design and manufacturing:

  • Integration of ZnSe conic surface
  • Combination of refractive and diffractive lenses for maintaining low F number and Athermal perperties without mechanical compensation need.
  • Chalcogenide material can be combined in design and manufacturing to approach the expected compensation for thermal expansion.

Off-The-Shelf LWIR lenses

Off-The-Shelf LWIR lenses

Opto-Mechanical Property Specification
Focal Length 9 mm 18 mm 35 mm 50 mm 75 mm 100 mm 250 mm
F# 2.0 0.9 1.0 1.0 1.0 1.0 1.1
Wavelength 8 μm - 12 μm 8 μm - 12 μm 8 μm - 12 μm 8 μm - 12 μm 7 μm - 14 μm 8 μm - 12 μm 7 μm - 14 μm
Image Diagonal 4.5 mm 18 mm 7 mm 14 mm 5 mm 18 mm 10.2 mm
Average Transmission >94% >85% >85% >85% >85% >85% >85%
Circular FOV 42.5º 53º 11.4º 15.94º 60.35º 10.3º 2.3º
Back Focus Distance 6.25 mm - 16.64 mm 14.5 mm 14.8 mm 18.4 mm -
Back Working Distance 2.75 mm 10.9 mm 8.44 mm 8 mm 10 mm - 22.80
Dimension Length 16.67mm, Φ23mm Length 33.63mm, Φ41mm Length 49.07mm, Φ48mm Length 79.65 mm, Φ70 mm Length 80 mm, Φ86 mm Length 143.8 mm, Φ112 mm Length 366.5 mm, Φ247 mm
Focus Type Manual Focus Manual Focus Manual Focus Motorized Focus Manual Focus Manual Focus Motorized Focus
Focus Range - 1m to infinity 1m to infinity - 1m to infinity 5m to infinity -
Mount Type M19*0.5 M41*0.75 M34*0.75 M55*1 M34*0.75 M55*0.75 -
Detector 160*120 pixels, 35 μm 320*240 pixels, 45μm 160*120 pixels, 35 μm 320*240 pixels, 45μm 160*120 pixels, 35 μm 320*240 pixels, 45μm 320*256 pixels, 25μm
Operating Temperature - 20℃ to +60℃
Storage Temperature - 40℃ to +80℃
External Coating AR AR DLC DLC DLC AR DLC
Humidity 100%RH at 26℃ and 74%RH at 35℃ for 24 hours
Opto-Mechanical Property Specification
Focal Length 4mm 5mm 6mm 50mm 75mm 100mm 400mm
F# 1.0 1.0 1.0 1.0 1.0 1.0 1.8
Wavelength 8μm-14μm 8μm-14μm 8μm-14μm 8μm-12μm 8μm-12μm 8μm-12μm 7μm-14μm
Image Diagonal 10mm 10mm 10mm 12mm 12mm 15.2mm 10.2mm
Average Transmission >85% >85% >90% >85% >85% >85% >85%
Circular FOV - 90º 90º 13.69º 9.15º 8.69º 1.46º
Back Focus Distance - 12.9mm - 14.5mm 19.76mm 22.8mm 22.8mm
Back Working Distance 7.5mm - 8.3mm 8mm - - 11.1mm
Dimension Length 46.41mm, Φ44mm Length 29.5mm, Φ30mm Length 29.3mm, Φ34mm Length 79.65mm, Φ70mm Length 103.88mm, Φ100mm Length134.3mm, Φ112mm Length 428mm, Φ240mm
Focus Type Manual Focus Manual Focus Manual Focus Motorized Focus Manual Focus Motorized Focus Motorized Focus
Focus Range 1m to infinity 1m to infinity 1m to infinity - 1m to infinity - -
Mount Type M24*1 M24*1 M24*1 M45*1 M34*0.75 M59-12Teeth -
Detector 320*240 pixels, 25μm 320*240 pixels, 25μm 320*240 pixels, 25μm 320*240 pixels, 45μm 160*120 pixels,   35 μm 320*240 pixels, 38μm 320*256 pixels, 25μm
Operating Temperature - 20℃ to +60℃
Storage Temperature - 40℃ to +80℃
Humidity 100%RH at 26℃ and 74%RH at 35℃ for 24 hours

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Joined: May 4th, 2017
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