Periodicity analysis on cat-eye reflected beam profiles of optical detectors

Suppressing retroreflection based on cubic phase mask

“…Wiener filter is widely used in image reconstruction due to its computational efficiency. The transfer function of wiener filter can be written as (5) where K is the noise-to-signal ratio which can be tuned in practical application. The reconstructed image can be obtained by (6) Where fi(x,y) is the decoded image and Fo(u,v) is the intermediate blurred image in frequency domain.…”

“…Since most of the photoelectric devices have sensors or reticles fixed to their focal planes, when they are illuminated by a laser, the echo wave is higher than the diffuse targets by 2-4 orders of magnitude on average, named as retroreflection effect 1,2 , also known as "cat's-eye" effect [3][4][5] . By means of applying an active laser reconnaissance technique based on the retroreflection, some passive photoelectric equipment, such as cameras, telescopes, and rifle sights, could be detected with high directional precision, which makes the optical devices easily exposed with active laser detection technique.…”

Design of an Active Laser Mini-Camera Detection System Using CNN

“…In general, traditional cat-eye target detection systems are developed based on bistatic optical designs [4], [9], [10], where the transmitting and receiving optical axes are separated. These systems perform well when detecting larger, traditional cat-eye targets, but do not perform well when detecting mini-cameras.…”

Mechanisms of active detection on micro-cameras based on cat-eye effect with different incident angles

“…The advantage of using a cat-eye system in detecting cameras is the reflecting mirror inside the camera will always reflect the incident lights back to the light source and it's unpreventable unless someone coats the camera lens, but this makes the camera unable to work. Thus, the cat-eye effect theory has been used and applied in many research for detecting eye-cat targets [5][6][7][8].…”