چكيده به لاتين
Abstract:
Nowadays, with development of science and technology, guided weapons with high accuracy has been prevailing. In order to have an effective defense against these weapons, a laser defense system called laser warning system (LWS) is needed. This system can be used for countermeasure against bombs, laser guided missiles, laser rangefinders (LRFs) and laser target designators (LTDs). Having a good reaction against laser threats, it is necessary to first detect the kind of threat, then measure the direction and angle of arrival with good accuracy.
In this thesis, we investigate all types of laser threats and their parameters, and also some methods for detection of these threats has been investigated. Then a system model for laser warning receiver has been introduced which we are able to investigate all types of wheather conditions and effects of every radiatition that emmits from the sun surface and hits to the receiver, based on it. The effects of change in parameters for operation of the receiver was studied as well.
In chapter 4, a new structure for an optical array in laser warning receiver (LWR) is introduced. According to the laser threats wavelengths (0.5 – 1.6 µm) and our desirable field of view, we used 6 lenses for gathering the incident radiation and optimized the optical array using genetic algorithm. Lenses’ radius, their semi diameter, their distance from each other, lenses’ thickness and the kind of glass used in them was chosen in a way that we access a very high transmission coefficient. Also the optical reflection and absorption of the array decreases at the same time. After optimization, the obtained optical transmission is up to 82% and the obtained optical reflection and absorption is less than 15%. Total aberration of the incident ray decreased notably and the results showed that this parameter is less than 2µm in the worst case. The laser spot diameter which is focused on the detector is smaller than 300 µm in the worst case and total track of the array is 66.819 mm and effective focal length and F/# parameter are small as possible as they can be which cause to high quality of the light’s focus on the detector and smaller dimension and lighter weight for the receiver.
The offered structure has a remarkable signal to noise ratio (SNR) because of using optical devices with appropriate arrangement and very good optical transmission coefficient. The receiver’s operation in far distances from laser sources and in hazy conditions and low temperatures is quite suitable as well.
Also an arrangement for these arrays is proposed that enables the receiver to detect the angle of arrival with 10 degrees of accuracy and this accuracy is so beneficial in detection of the laser sources position.
Keywords: Laser Warning Receiver, Angle of Arrival, Optical Transmission, Field of View
