Information collected using long-range surveillance techniques such as hidden cameras is used in modern warfare methods such as mobile surveillance or static monitoring. Detection, recognition and identification are the three different phases of surveillance.
Detection at long range may denote a variation or a change in the scene without any clear details whether it is a friend or an enemy.
Recognition occurs in a mid-distance range and provides clear details for evaluating the threat. Identification, however, is a short-range function and requires vast data and high quality images for clearly determining he threat.
With the development of digital imaging technologies, the resolution of long-range targets has been increased to achieve improved recognition and detection capabilities. High resolution cameras are relatively low-cost solutions providing good quality images in daylight.
However, they have limited capabilities of producing actionable data under low light conditions. Near infrared (NIR) LEDs / laser illuminators are therefore used as an alternative to provide light that cannot be detected by the naked eye.
High quality images are difficult to obtain using cameras with low light vision. To overcome this issue, PHOTONIS has developed a low- light CMOS camera – Nocturn with high resolution and high frame rate, for long-range observation in low lighting conditions.
It is available in various connection options such as USB3 (color), PAL (monochrome), NTSC, USB and Gigabit Ethernet.
Nocturn – a Low-Light CMOS Camera
Nocturn consists of a large 9.7 x 9.7µm pixel array with a rolling shutter. The array has up to 100Hz frames rates for providing high- quality images of both moving and static objects. Micro lenses have been provided to enhance the image sensitivity in low light conditions and quantum efficiency near 80% at peak efficiency. Figure 1 shows the QE curve of Nocturn.
Figure 1. QE curve of Nocturn
The CMOS camera offers SXGA (1280x1024) resolution with real-time imaging capabilities in the NIR and visible spectrum, and has low power consumption. With a wide range of standard CS mount lenses, the camera is capable of providing up to 8x digital zoom.
Test on long-range capabilities of Nocturn
A comparative test was carried out to determine the long-range characteristics of the Nocturn camera by analyzing the probability of detection, recognition, and identification of an adult human.
Apart from Nocturn, comparative testing was performed also on a low light CMOS (LLL CMOS) and a low light CCD (LLL CCD) at two light levels: quarter moon (15mlux) and full moon (100mlux). Figures 2, 3 and 4 show the probability range of detection, recognition and identification in varied lighting conditions.
Figure 2. Detection probability in varied lighting conditions
Figure 3. Recognition probability in varied lighting conditions
Figure 4. Identification probability in varied lighting conditions
Further, to evaluate the Signal to Noise (SNR) performance, Lux transfer curves were produced for all the cameras at same frame rates.
Although Nocturn is capable of 100fps, it was compared at 30fps – a limiting rate of LLL CCD cameras. Figure 5 shows the SNR comparison graph.
Figure 5. SNR comparison graph
It is evident from the charts above, the overall performance of the LLL CCD camera is lower than that of the CMOS sensor performance owing to its low resolution and low pixel numbers on target. A 50% reduction in identification range was also observed for both LLL CMOS and LLL CCD.
In comparison, Nocturn showed a reduction of less than 15%, and the difference in SNR indicates the ability of the Nocturn to produce good quality images to quarter moon illumination. LLL CCD and CMOS, however, showed a good performance down to approximately half moon illumination.
Nocturn can provide more than 90% detection probability at quarter moon at 1000m, over 80% identification at 200m and greater than 75% recognition capability.
The sensitivity of Nocturn was found to be three times of the ISO12232 minimum image quality limit. In addition, the actual images obtained from the camera in both color and monochrome versions display the capabilities of identifying unique characteristics of human such as the color of the shirt and eyeglasses. Figure 6 shows the monochrome and color actual still images of Nocturn at 15mlux.
Figure 6. Monochrome and color actual still images of Nocturn at 15mlux
From the experimental findings, it can be observed that the Nocturn provides excellent daylight images via low light, making it ideal for low-light conditions, specifically at long range. In addition, the high SNR provides excellent contrast at quarter moon, enabling target identification at long distance.
The small size, weight and power consumption (SWaP) of the Nocturn camera ensures remote installations and hand-held devices such as rifle sights or monocular devices. Moreover, high SXGA resolution offers high-quality video in applications such as UAVs.
About PHOTONIS Technologies
PHOTONIS is a leader in the innovation and manufacture of ion, electron and photon detection and amplification components that are the critical enabling technology within many analytical instruments. PHOTONIS is a market leader in image intensifiers, digital low-light cameras, mass spectrometer detectors, nuclear safety, power tubes and custom detection components for physics and space research instruments. Their products are manufactured in several facilities globally, including PHOTONIS France, PHOTONIS Netherlands and their three facilities that comprise PHOTONIS USA.
Their products are award-winning for their innovation and quality. PHOTONIS products can be found on most space telescopes, in many high-energy physics research laboratories, and in night vision goggles around the globe where highly sensitive low light amplification is required. They are also key suppliers to the nuclear industry with our gamma and neutron detectors, and to defense industries globally with digital and portable solutions.
This information has been sourced, reviewed and adapted from materials provided by PHOTONIS Technologies S.A.S.
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