Ultraviolet (UV) Optics/Detectors: For Solar-Bind Imaging & Detections Application Note
When high-voltage equipment discharges electricity, corona discharge, arc flash, or arc discharge may occur depending on the electric field strength, during which electrons in the air continuously gain & release energy, emitting UV rays. UV imaging utilizes this principle to receive UV signals. UV optics are involved in solar-bind imaging. Solar radiation in the wavelength band of 190-285nm is completely absorbed by the ozone layer when passed through the atmosphere. The scattering of other components & the surface ozone in the atmosphere below the ozone layer also absorbs it, creating a natural “solar-blind” near the ground – where the naturally occurring solar signal is almost completely undetectable
Operation Principle
UV Lens
In UV imaging, UV light signals released are processed & overlapped with the image formed by visible light on a screen, allowing for the position & intensity of the electrical discharge to be determined. Our UV lens is developed for use across x-rays & visible light within the electromagnetic spectrum. Our UV lens has a wavelength over a range from 200nm to 385nm. Its apochromatic lens allows images to be formed across UV to visible light spectrums. It can be used in UV cameras or image intensifier tubes for observation. The addition of a close-up lens allows for obscure fingerprints on surfaces of materials, such as glass, to be detected & efficiently removed.
| Model | Range |
| Fixed Focus Lens | EFL: 10 ~ 300 mm |
| Zoom Lens (1.5x) | EFL: 40 ~ 60 mm |
| Super Achromatic Lens | Wavelength: 200 ~ 1100 nm |
UV lenses encompass features of chase light caliber, & high accuracy & resolution. In solar-bind imaging, the existence of light in the solar blind ultraviolet band on the earth usually consists of only three cases: (1) an unnatural danger signal, such as gunfire, explosive explosion, fire & corona generated by high-voltage transmission line leakage; (2) a man-made solar-bright ultraviolet light source; (3) abnormal weather such as strong lightning. This entails that if a solar blind UV signal is detected in the “dark room”, a specific event, such as a missile attack, occurs.
The area within 15 km of the surface layer is free from noise interference, allowing for the target to be detected without sophisticated image processing.
The key specifications of the UV wide-angle lens are listed below. Compared to similar products in the market, we offer small wide-angle distortion and better pixel resolution, useful for solar-blind imaging and detection.
| Wavelength | 254+/-20nm |
| Focal Length | 9.2mm |
| BFL | 13.5mm |
| Aperture | F#3.6 (manually tunable) |
| FOV (Imaging Plane) | 18mm |
| FOV (Angle) | 90° |
| Working Distance | 20cm ~ ∞ |
| Angle Distortion | </=2% |
| MTF | 70Ip/mm>0.3 |
| Mount | C-mount |
| Working Temperature | -40 ~ 50 °C |
UV Detectors
UV detectors include a UV image intensifier tube, UV ICCD/ICMOS, and solar-blind UV filter components. These are critical assemblies to form the hard core of a UV imaging/detection system. Combining the capabilities of UV detectors and UV lens/optics, we are able to offer customization solutions for different applications.
Applications
UV imaging technology could be used in but not limited to the following application scenarios:
- Ship fog breaking piloting
- Forest fire alarm
- Power grid safety monitoring
- Maritime search and rescue
- Satellite navigation
- Aircraft fog breaking blind drop
- Missile approach warning
- Document security feature identification under sunlight conditions (passport, license, etc.)
- Close-range criminal investigation; search for potential fingerprints, footprints, hidden blood prints, fibers, etc
In power & high-speed rail systems, UV imaging could be used to achieve high-sensitivity corona and arc detection as shown in Fig. 3 left; 100% filtered out of the sunlight during full-day blindness, to achieve high sensitivity corona and arc detection.
Another critical application is the forest fire alarm. Compared to existing fire alarm technology which cannot penetrate the “dark room” atmosphere under sunlight, UV imaging provides solar blindness adaptability. Secondly, it is not affected by environmental/weather changes and high-temperature interference sources. Utilizing high-sensitivity UV imaging technology, the occurrence of a fire in real-time can be detected several kilometers away. It can be covered by setting up a gimbal (as shown in Fig. 3 right) or installing it on a helicopter to cover the entire forest area.
| Wavelength | 185 – 330nm |
| Peak Response | 245nm |
| Diameter of Cathode | 18-25mm |
| Irradiation Sensitivity | 40 mA/W@254nm |
| Resolution | 20lp/mm |
| Background Irradiation | 5×10-11W/m2 |
| Irradiation Gain | 108(cd/m2)/(W/m2) |
| Size (mm x mm) | Φ35.5 x17.6/Φ45.5 x18 |
| Working Temperature | -55 to 70 °C |
| Parameters | 18-ICCD | 25-ICCD |
| Wavelength | 185 – 330 nm | 185 – 330 nm |
| CCD Size | Half inch | Half inch |
| CCD Pixels | 752 x 582 | 752 x 582 |
| Magnification | 1:2.2 | 1:3.1 |
| Resolution | 15 | 15 |
| Sensitive Area | 14mmx10.5mm | 20mmx15mm |
| Output signal | Composite Video /ethernet100fps | Composite Video |
| Input Voltage | DC 12, 5 | DC 12, 5 |
| Working Temperature | -25 to 45 °C | -25 to 45 °C |
| Wavelength | 264 +/-3nm | 264 +/-3nm | 264 +/-3nm |
| Peak Transmission | >20% | >20% | >20% |
| Bandwidth | 20+/-3nm | 20+/-3nm | 20+/-3nm |
| Serial | RMF-A | RMF-B | RMF-C |
| Size | Φ31.5 x21.5 | Φ31.5 x26.3 | Φ37 x21.5 |
| Aperture | Φ22.5 | Φ22.5 | Φ30 |
| Mass | <40g | <50g | <60g |
| Working Temperature | -40 to 60 °C | -40 to 70 °C | -40 to 60 °C |
| Reliability | GJB-369A-98 and GJB-150 | GJB-369A-98 and GJB-150 | GJB-369A-98 and GJB-150 |