DESC:TECHNICAL FIELD
The present invention relates an innovative Laser Warning System (LWS), meticulously engineered to safeguard terrestrial, aerial, or maritime platforms against laser-guided menaces. Specifically, the invention encompasses a novel method and apparatus designed for the precise detection and accurate determination of the directional origin of laser radiation or collimating optical sources. This system is characterized by its remarkable angular resolution capability, leveraging advanced detection technology and sophisticated algorithms to discern and localize the source of laser threats with unprecedented accuracy. Through its integration, the invention significantly enhances the defensive measures of various platforms, providing a critical layer of protection against the evolving landscape of laser-guided threats.
BACKGROUND

The laser warning receiver is one of the most important early warning sensor that is commonly used on various military platforms like armoured vehicles, aircrafts and ships. Various types of laser ammunitions are in use to pinpoint and home on to the target with high accuracy. The proliferation of laser guided threats in modern combat has led the researchers and many companies around the world to develop systems that can detect and determine the direction of laser sources.
The angle of arrival of a laser can be detected using various techniques like imaging, masking and time delay etc. the disclosed particular technique is related to the encoded masking technique category.
US5428215 titled “Digital High Angular Resolution Laser Radiation Detector (Harlid)” discloses an apparatus for detecting and determination of laser direction based on an encoded mask. The system includes an encoded mask that is placed in front of a linear array of radiation detectors arranged in a single plane, the distance between encoded mask and detectors are fixed at a predetermined distance. The mask contains a plurality of slits and each slit is located above the plurality of radiation detectors which gives a plurality of output signals corresponding to each slit and detector. The slits encoded on the mask are designed such a way that the output of the radiation detectors will give a Gray coded output. The slits are positioned above the radiation detector parallel with each other but perpendicular to the axis of the detector array. A well collimated radiation beam, incident on the apparatus containing Gray coded mask will project images of the slits onto the plane containing radiation detectors, these images are depending on the position of slits and angle of arrival of the beam. These images will create digital output signals from radiation detectors. The angle of arrive of laser will be determined from these output signal of the radiation detectors.
US4857721 titled “Optical Direction Sensor Having Gray Code Mask Spaced From A Plurality Of Interdigitated Detectors” discloses an apparatus for detecting and determining the angle of arrival of a radiation beam. The devices includes a first mask having one or more slit apertures placed on above of a second binary encoded mask at a fixed distance. The binary encoded mask is designed such a way that it uses a gray encoding scheme, this gray coding scheme senses the angle of arrival of a beam of radiation and gives a set of differential signal via interdigitated detector responsive to the beam’s angle of arrival. Detector’s proxy processing electronics will provide a plurality of digital signals these digital signal forms a digital code or word corresponding to the angle of arrival of the incident radiation.
WO2006/061819 titled “Complementary Masks” discloses an apparatus for detecting the direction of radiation beam of a collimated beam. The system contains a pair of encoded masks with detectors and at least one aperture. The distance between the pair of masks and aperture is predetermined based on the Field of view coverage. The determination of angle of arrival is similar to the approach mentioned in the US pat no: 4857721, except in this discloses the encoded mask is pair of masks contains one mask and a complementary mask. A pair of detectors for respective pair of masks and a summator circuit for respective pair of detectors. One detector of the pair is coupled optically with mask and second detector is optically coupled with complimentary mask. The summator being electrically coupled with the respective pair of detectors, wherein the mask is optically encoded and the complementary mask is complementarily optically encoded with respect to the mask, the aperture distributing light differently on the pair of masks for light impinging on the apparatus from different directions. The summator circuit produces subtracted signal between mask and complementary detectors signal, which enhances the power dynamic range of the system.
US2010/0208245A1 titled “Apparatus And Method For A Light Direction Sensor” discloses an apparatus that can detector angle of arrival in both azimuth and elevation direction. The system consists an image sensor, a patterned mask with plurality of slits and a spacer attached to the image sensor. The mask with slit pattern that is placed above image sensor will create a diffraction pattern as light passes through the slit patterned mask. The method operates by receiving a beam of light onto a patterned mask, where in the patterned mask as a plurality of a slit segments. Then, diffusing the beam of light onto an image sensor and determining the direction of the light source.
The major disadvantage of the reference patents US 5428215, US 4857721 and WO2006/061819 that uses shadow masked approach, is that it can resolve the angle resolution only in one direction i.e., either in azimuth or elevation. US Pat no: US 2010/0208245 disclosed a method for determining the resolution both in azimuth and elevation using an imaging focal plane array sensor, but the sensor is required to do a specialized image sensor processing to determine the angle of arrival.
There still remains a conspicuous necessity for a technical solution that efficaciously addresses the delineated challenges, thereby providing a method and apparatus capable of detecting and precisely determining the direction of laser radiation or collimating optical sources with superior angular resolution. This invention delineates an innovative approach, incorporating state-of-the-art sensors and cutting-edge computational algorithms, designed to enhance the accuracy of laser source localization. By optimizing the integration of hardware sensitivity and software intelligence, the proposed solution offers a significant leap in the capability to not only detect the presence of laser threats with unparalleled efficiency but also to ascertain their origin with an unprecedented degree of angular precision. Such advancements represent a pivotal development in protective measures for military and civilian assets alike, ensuring a robust defense mechanism against the increasing sophistication of laser-guided threats.

SUMMARY
This summary is provided to introduce concepts related to an innovative Laser Warning System (LWS), meticulously engineered to safeguard terrestrial, aerial, or maritime platforms against laser-guided menaces. Specifically, the invention encompasses a novel method and apparatus designed for the precise detection and accurate determination of the directional origin of laser radiation or collimating optical sources. This system is characterized by its remarkable angular resolution capability, leveraging advanced detection technology and sophisticated algorithms to discern and localize the source of laser threats with unprecedented accuracy. Through its integration, the invention significantly enhances the defensive measures of various platforms, providing a critical layer of protection against the evolving landscape of laser-guided threats.
In an embodiment of the present invention, an apparatus is designed for the precise detection of the angle of arrival (AoA) of a collimated radiation beam. This apparatus incorporates an attenuated optical encoded mask, specifically configured to intercept and modulate the incoming collimated beam contingent upon its angle of incidence. To this end, an amplifier is directly linked to the mask, tasked with amplifying the modulated beam for enhanced signal clarity. Subsequently, a pulse shaping circuit, connected to the amplifier, molds the amplified beam into a specific waveform, facilitating accurate signal processing. A multiplexer, in turn, selects and relays the shaped signal to an analogue to digital converter, which transforms the analogue signal into a digital format for computational analysis. The digital signal is then processed by a sophisticated processor, be it a microcontroller, microprocessor, FPGA, or GPU, engineered to deduce the AoA of the collimated beam with notable angular precision across one or more directional axes. Uniquely capable of determining the AoA in both one-dimensional and two-dimensional planes, this apparatus represents a significant innovation in the field of radiation beam analysis and detection.
In an embodiment of the present invention, a method for accurately detecting the angle of arrival (AoA) of a collimated radiation beam is disclosed. This method encapsulates a sequence of precisely defined operations. Initially, the method entails the reception of the collimated radiation beam by an attenuated optical encoded mask, which modulates the beam contingent upon its angle of incidence, thereby encoding angular information directly into the beam's structure. Following this modulation, an amplifier, which is interconnected with the attenuated optical encoded mask, amplifies the modulated beam to enhance its detectability. Subsequent to amplification, a pulse shaping circuit, linked to the amplifier, processes the amplified signal into a predetermined waveform, optimizing it for further analysis. The method further involves the use of a multiplexer, connected to the pulse shaping circuit, to select and relay the shaped signal for additional processing. An analogue to digital converter, connected to the multiplexer, then converts the selected analogue signal into a digital format, facilitating computational analysis. The culmination of this method is the computing of the AoA of the collimated beam, executed by a processor, selected from a range including a microcontroller, a microprocessor, an FPGA, and a GPU, connected to the analogue to digital converter. This processor computes the AoA based on the digital signal with high angular accuracy across at least one directional axis. Importantly, the method is adept at determining the AoA in both one-dimensional and two-dimensional planes, thereby offering a comprehensive solution for analyzing the directional attributes of collimated radiation beams.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The detailed description is described with reference to the accompanying figures.
Figure 1 illustrates an exemplary Field of view for azimuth and elevation represented in cartesian coordinate system, in accordance with an exemplary embodiment of the present invention.
Figure 2 illustrates a schematic diagram representing the one directional angle of arrival detection method, in accordance with an exemplary embodiment of the present invention.
Figure 3 illustrates a schematic diagram representing the two directional angle of arrival detection method, in accordance with an exemplary embodiment of the present invention.
Figure 4 illustrates an apparatus for the implementation of one directional angle of arrival method, in accordance with an exemplary embodiment of the present invention.
Figure 5 illustrates an apparatus for the implementation of two directional angle of arrival method, in accordance with an exemplary embodiment of the present invention.
Figure 6 illustrates an apparatus for the conversion of radiation sensor output current to optimum voltage signal, in accordance with an exemplary embodiment of the present invention.
Figure 7 illustrates an apparatus for the conversion of optimum analogue voltage from different channel to equivalent digital signal, in accordance with an exemplary embodiment of the present invention.
Figure 8 illustrates a digital block for conversion of real-time digital signal from sensors to attenuation normalised signal for digital comparison, in accordance with an exemplary embodiment of the present invention.
Figure 9 illustrates a digital block for conversion of real-time digital attenuation normalised signal to 2bit noise compensated digital representation, in accordance with an exemplary embodiment of the present invention.
It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative methods embodying the principles of the present invention. Similarly, it will be appreciated that any flow charts, flow diagrams, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

DETAILED DESCRIPTION
The various embodiments of the present invention describe about a novel method and apparatus designed for the precise detection and accurate determination of the directional origin of laser radiation or collimating optical sources. This system is characterized by its remarkable angular resolution capability, leveraging advanced detection technology and sophisticated algorithms to discern and localize the source of laser threats with unprecedented accuracy. Through its integration, the invention significantly enhances the defensive measures of various platforms, providing a critical layer of protection against the evolving landscape of laser-guided threats.
In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of systems.
However, the systems and methods are not limited to the specific embodiments described herein. Further, structures and devices shown in the figures are illustrative of exemplary embodiments of the present invention and are meant to avoid obscuring of the present invention.
Furthermore, connections between components and/or modules within the figures are not intended to be limited to direct connections. Rather, these components and modules may be modified, re-formatted or otherwise changed by intermediary components and modules.
The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
It should be noted that the description merely illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present invention. Furthermore, all examples recited herein are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
In an embodiment of the present invention, a method and an apparatus for detecting and determining the direction of laser radiation or collimating optical sources with high angular resolution.
A novel method for determining the angle of arrival is disclosed. The method uses prime and resolution channels for detecting and determination of angle of arrival instead of Gray code. The method is proposed for determining the angle of arrival in one direction and it can be extended to find the angle of arrival in both azimuth and elevation using the same number of detectors that are used for one direction sensor. The method can be implemented using an encoded mask and a radiation detector PCB placed at a predetermined distance. The method uses Analog-to-digital converter (ADC) in combination with mux which will reduce the number of ADC channel required. This reduces the cost as well as processing resources. The usage of ADC provides the capability to continuously measure the radiation detector output, this will allow to identify faulty sensor immediately. If this is identified during the operation with an angle correction algorithm, a corrected optimum possible angle can be calculated. The method measures the relative amplitude in comparison with the reference channel. This enables adaptive thresholding. The adaptive thresholding enable to improve noise reduction and increase in dynamic range. This also improve the false detection due to sun glitch.
In an embodiment of the present invention, a method and apparatus for the detection of angle of arrival of a collimated radiation beam suitable for one and two directions with high angular accuracy is disclosed. It consists of diverse attenuated optical encoded mask, amplifier, pulse shaping circuit, multiplexer, analogue to digital converter and microcontroller/microprocessor/FPGA/GPU.
In another embodiment of the present invention, the method consists of multiple channels which cover the total FOV. The prime channel covers the total FOV and allow the total radiation intensity without any change. Resolution channel’s also covers the total FOV, but these Resolution channels again divided into different transparency sectors which restrict the relative intensity of the radiation. First resolution channel is divided into two half FOV sectors which allow two different intensity levels of radiation, the next resolution channel is divided into four FOV sectors and third resolution channel is divided into Eight FOV sector. These different FOV sectors of resolution channels allow different radiation intensity levels as per the transparency of each sector. By comparing the radiation levels of resolution channel with prime channel the angle of arrival with high accuracy can be obtained.
In another embodiment of the present invention, the method is implemented using an example apparatus. The apparatus consists of an encoded mask and a radiation detector plane separated by a predefined distance. The encoded mask is with different dielectric coatings that give different transparency sectors as required for prime and resolution channels. The radiation detector plane consists of a set of radiation detectors, each radiation detector is coupled with a respective prime and resolution channel. When the collimated radiation falls on the encoded mask an image of the encoded mask will fall on the detector plane. When the radiation is incident on the apparatus at different angles the mask image which allow different intensities will wander on the detector plane, due to these different light intensity levels, different intensity levels of electrical signal will be generated for prime and resolution channel. By comparing the intensities of the resolution channels with prime channel intensity through which sectors of resolution channel the radiation is transmitted can be found out, through which the angle of arrival can be inferred.
In another embodiment of the present invention, the method is extended for detection of angle of arrival of collimated radiation beam in both azimuth and elevation with high angular accuracy. The method consists of multiple radiation intensity measurement channels which covers both in azimuth and elevation directions. Prime channels cover whole FOV both in azimuth and elevation and is allow the total radiation intensity without any change. Resolution channels also cover whole FOV, but the FOV of resolution channels are divided into FOV cells which covers only a predetermined FOV, these FOV cells are expected to have different radiation transparency and allow different levels of intensity passes through it. Resolution channel-1 is divided into four quadrants FOV cells with four different transparencies and next resolution channel-2 is divided into sixteen FOV cell by dividing each FOV cell of resolution channel-1 into four sub FOV cells with same transparencies as resolution channel-1. The next resolution channel-3 divided into sixty-four FOV cell by dividing each FOV cell of resolution channel-2 into four FOV cell with same transparencies as of resolution channel-1. By comparing the intensities of resolution channel with prime channel intensity the angle of arrival in both azimuth and elevation can be identified.
In another embodiment of the present invention, the method is implemented using an example apparatus. The method implemented using an encoded mask and radiation detector plane, the encoded mask is transparent in the concerned radiation band, the detector plane is located at a predetermined distance from the encoded mask. The encoded mask is with apertures of dielectric coated with different transparencies. The detector plane consists of a set of radiation detectors located centrally below the apertures of the encoded mask, each aperture and detector make a channel. The prime channel covers the whole FOV with full transmission, and resolution channel-1 has four FOV cells coated with four different dielectric coating with different transparencies, which allow four different level of intensities to pass. The next resolution cahnnel-2 has sixteen FOV cells by dividing each FOV cell of resolution channel-1 into four cell with same transparencies as resolution channel-1. The next resolution channel-3 is divided into sixty-four FOV cell by dividing each FOV cell of resolution channel-2 into four cells with same transparencies of resolution channel-1. This sequence of dividing resolution channel FOV cell into four cell for the next channel with same transparencies as first resolution channel may follow till the required resolution. By comparing the detector signal amplitudes of resolution channel with prime channel, the angle of arrival may be determined with height accuracy both in azimuth and elevation.
In another embodiment of the present invention, the combination of ADC with mux will reduce the need for multiple ADC.
In another embodiment of the present invention, the usage of reference channel based thresholding will help to identify faulty sensor on the fly. The system can work with reduced resolution even when there is a faulty sensor. Usage of ADC based relative thresholding based on reference channel will reduce the false sensing as it will eliminate background radiation effect. Digital Multiplication of calibrated reference input with angle channel will reduce the noise as the noise will not be coherent.
In another embodiment of the present invention, the usage of mask weightage based angle calculation and the optimised orientation between different resolution channel will reduce number of bit transition occurs for minimum angular change thus reduce transition angle error.
In another embodiment of the present invention, usage of low gain, high gain sensor will eliminate possibility of saturation and increase the dynamic range.
The present invention provides an apparatus that utilises multiple discrete sensors that can detect collimated incoming radiation and determine the angle of arrival in both elevation and azimuth directions. The apparatus includes an encoded mask and a plurality of radiation detectors arranged on a single PCB. The encoded mask is optically coupled with radiation detectors, pulse shaping circuit, amplifier, mux and ADC, which gives a digital signal outputs for both azimuth and elevation simultaneously.
Figure 1 illustrates an exemplary Field of view for azimuth and elevation represented in cartesian coordinate system, according to an exemplary implementation of the present disclosure. The example of Total Field of View (TFOV) 100, 90 deg x 90 deg FOV in both azimuthal and elevational directions are represented in a Cartesian coordinated system, and TFOV 100 is divided into four equal FOV’s quadrants 101 , 102,103 and 104.
Figure 2 illustrates a schematic diagram representing the one directional angle of arrival detection method, according to an exemplary implementation of the present disclosure. This figure describes the radiation intensity control for different channel for detecting angle of arrival. The scheme is for finding the direction arrival of the radiation in one direction, this scheme consists of one prime channels 10, and resolution channels 11,12,13,14 … etc. The prime channel 10 is expected to give an output electrical signal of certain level in whole TFOV 100. The resolution channel 11 is divided into two half sectors with one transparent and less transparent sectors. And is expected to give an output signal of two different levels for two FOV sectors. This electrical signal level will be compared with prime channel level and will decide the direction of light. The resolution channel 12 is divided into equal transparent and less transparent sectors. The FOV sectors 121, 122, 123, 124 width is half of the width of first resolution channel-11 and when collimated radiation direction incident on the resolution channel 12 and it is expected to give an output electrical signal of different levels depending on the transparency of the FOV sectors, transparent and less transparent sectors. The next resolution channel 13 is divided into equal FOV sectors of 131,132, 133, 134, 135, 136, 137, 138 the width of resolution channel 13 FOV sector is half of the width of FOV sectors of resolution channel 12 and resolution channel 13 is expected to give an output signal of certain level only when the radiation direction coming from the FOV sectors. The next resolution sensor has FOV division opening sectors which is equal to half of the width of previous resolution sensors width. And in this sequence the resolution channel’s FOV opening sectors will be halved from the FOV opening sectors of previous resolution channel. The combination of prime and resolution channels outputs signal after electrical processing will give a digital coded word which is specific to the angle of arrival of optical radiation. The resolution of the disclosed method is limited by the resolution channels FOV sector width and number of resolution channels.
Figure 3 illustrates a schematic diagram representing the two directional angle of arrival detection method, according to an exemplary implementation of the present disclosure. This figure describes the radiation intensity control for different channel for detecting angle of arrival. the disclosed method is extended to determining the angle of arrival of the collimated radiation for both azimuth and elevation directions. The basic principle of the disclosed method is illustrated in figure-3, reference is now made to figure-3, where the example total field of view (FOV) 100 90 deg in azimuth and 90 deg in elevation is represented in a Cartesian coordinated system, and TFOV 100 is divided into four equal FOV quadrants 101, 102, 103 and 104 respectively. The two directional method consists of prime channel 20, , , and resolution channels 21,22,23, 24, 25… etc. the prime channel 20 is expected to give an output signal of certain value when the collimated radiations direction is coming from whole TFOV both in azimuth and elevation direction.
The resolution channel is also expected to cover the TFOV 100 of figure-1, and the TFOV is divided into a matrix of Azimuth and Elevation FOV cells, these FOV cells are expected to have different transparencies. The Azimuthal directional FOV sectors may be represented using Alphabet letters A, B, C, D etc. and elevation directional FOV sectors may be represented using numerical digits 1,2,3,4,5 etc. The intersection of Azimuth and elevation sectors will form a matrix of FOV cells. Resolution channel-1’s TFOV may be divided into two columns and two rows of equal FOV alternate transmission and less transparent sectors, each transmission sectors allowed FOV in azimuth is half of the azimuth FOV of quadrant 101 and in elevation direction is half of the elevation FOV of quadrant 101. The resolution channel-1 is expected to give an output electrical signal of four levels when compared with the prime channel signal level and each level is corresponds to four FOV cell. Resolution channel-2’s TFOV may be divided into four columns and four rows of equal FOV alternate transparent and less transparent sectors. Each FOV cell’s width and height may be half of width and height of resolution channel-1 FOV cell’s width and height. The alternate opening of FOV sectors may follow a sequence, wherein odd columns and even rows sectors FOV and even column and odd rows sectors FOV’s have certain transmission sectors. The resolution channel-2 is expected to give an output signal of 16 levels corresponding to 16 FOV cells. The combination of prime and resolution channels outputs will form a digital coded word after electronics processing, this digital coded word will determine the angle of arrival of collimated optical radiation.
Figure 4 illustrates an apparatus for the implementation of one directional angle of arrival method, according to an exemplary implementation of the present disclosure. It contains an encoded mask with dielectric coating as and an array radiation detectors placed on detector plane at a predetermined distance. The apparatus 400 consists of an encoded mask 30 and one linear array of radiation detectors 40. The encoded mask 30 is made of glass window or any other material that is transparent to the concerned electromagnetic radiation band and it is dielectrically coated with different transparent levels. The encoded mask 30 includes various transparency level sectors of 30(0,0), 30(1,1), 30(2,1), 30(2,2), 30(3,1), 30(3,2), 30(3,3), 30(3,4), 30(4,1), 30(4,2), 30(4,3), 30(4,4), 30(4,5), 30(4,6), 30(4,7), 30(4,8) etc., the transparency sections are stretched along parallel to the length of the mask. The radiation detector plane 40 consists of a set of radiation detectors 410,411, 412, 413, 414 etc. The radiation detector plane 40 is located at a predetermined distance of ‘h’ from the encoded mask 30. The radiation detectors may be made of any material for example silicon or any other material which is sensitive to the concerned electromagnetic radiation, each detector’s output is electrically connected to a proxy electronics circuit which digitise the detected detector’s output based on predetermined detector signal threshold level. The transparency sectors are located directly above of the radiation detectors. When the collimated radiation incident on the apparatus 400, the encoded mask 30 will form a shadow image on the detector plane 40, this shadow image will lead to plurality of radiation detector’s output. The encoded mask apertures lengths and positions are arranged in a pattern to generate the digital code, wherein the digital code is based on the method described in figure-2.
The aperture 30(0, 0) and detector 410 makes the prime channel of the apparatus, which gives the output certain relative value for the total field of view. The FOV sectors 30(1, 1) and detector 411 makes the resolution channel and gives the output of two electrical signal certain relative value only for half of the FOV. The apertures {30(2,1) ,30(2,2)}, {30(3,1), 30(3,2), 30(3,3), 30(3,4)}, {30(4,1), 30(4,2), 30(4,3), 30(4,4), 30(4,5), 30(4,6), 30(4,7), 30(4,8)}etc. and detectors 412, 413, 414 etc. form the resolution channels. And all the aperture and detector pairs are independent of each other in signal generation, the coverage in the normal direction may be achieved by including a reflector waveguide for each channel. When the collimated radiation incident on the apparatus 400 inclined at an angle with the detector array axis and due to this radiation based on the angle of arrival a particular digital code will be generated by the detector array. For a device having one prime and ‘n’ resolution channels there will be 2^n binary combinations may be possible, and the least angle of arrival that can be resolved by the apparatus will be TFoV/(2^n ).
Figure 5 illustrates an apparatus for the implementation of two directional angle of arrival method, according to an exemplary implementation of the present disclosure. It contains an encoded mask with dielectric coating as and radiation detectors place d directly below the different channel aperture of encoded mask on the detector plane at a predetermined distance. The device 500 consists of an encoded shadow mask 50, a set of radiation detectors located on a single detection plane 70.The purpose of the encoded mask 50 is to generate the digital code that is expected as per the figure-3. Figure-5 consists of detectors 7000, 7010, 7020, 7030, 7040 centrally located directly below the channels 50(00), , 50(10), 50(20), 50(30), 50(40) and 50(50).The encoded mask is made of thin glass or dielectric material or any other material that is transparent in the interested electromagnetic radiation. The encoded mask 60 forms a shadowed image on the detector plane 70 based on the masks pattern. The radiation detector plane 70 is located at a predetermined distance of ‘h’ from the encoded mask 60. The radiation detectors may be made of any material for example silicon or any other material which is sensitive to the concerned electromagnetic radiation, each of detector’s output is electrically connected to a proxy electronics circuit which digitise the detected detector’s output into certain relative value based on predetermined detector signal threshold level and mask attenuation. Each radiation detector and transparency matrix may be considered as a single channel. The detector 7000 and transparency window 50((00)) may be considered as prime channel, the prime channel will cover full FOV in both azimuth and elevation with maximum allowed intensity. The prime channel produces certain relative output signal for whole TFOV in azimuth and elevation.
The transparency window 50(10) and detector 7010 forms the resolution channel R1. The transparency window 50(10) width and height is same as prime channel but the channel is divided into a 2x2 matrix of FOV cells , each FOV cell covers half of TFOV in azimuth and in elevation and is having four different level of known transparency in the concerned radiation, when the collimated radiation passes thorough transparency window 50(10), the detector 7010 gives an output of certain relative value the amplitude of the signal value is depend on the FOV cell through which radiation is passes through.
By comparing the signal amplitude of resolution channel-1 amplitude with prime channel signal we can find out from which FOV cell of resolution cahnnel-1 the radiation is incident on the radiation detector 7010, which gives the angle resolution of a quadrant of TFOV.
In another embodiment of the present invention, as per the method described in figure 3, on the encoded mask an aperture 50(20) and detector 7020 forms the resolution channel-2 in the disclosed apparatus 500. The aperture 50(20) is not a single aperture extended in one direction but a square shape area with 4x4 matrix of different transparency apertures extended both in azimuth and elevation directions, the resolution channel-2 maximum height and width is equivalent to height and width of resolution channel-1. The channel consists of a set of transparent and less transparent, each cell’s FOV is one fourth of the total FOV in elevation and in azimuth direction. In the disclosed example of figure-4, the FOV cell B3 of column B and row 3 covers a FOV of 22.5 deg in azimuth and 22.5 deg in elevation. The resolution channel-2 is having total 16 FOV Cells, each quadrant consists of four FOV cells and these four FOV cells will have four different transparency levels same as of resolution channel-1.When the collimated radiation incident on the apparatus 500, a shadowed image of resolution channel-2 will be formed on the detector plane, wherein the detector 7020 is located centrally directly below the aperture 50(20). The encoded image on the detector plane 70 consists of a matrix of radiation with different intensity regions and encoded image will wander on the detector plane 70 based on the collimated radiation angle of incidence, the detector 7020 will give an output of certain value based on which intensity region of radiation moved on to the detector 7020. The wondering of encoded mask may be confined to within resolution channel-2 square area using four thin metal sheets placed on all the four sides of the resolution channel-2.
As per the method described in figure 3, on the encoded mask an aperture 50(30) and detector 7050 forms the resolution channel-3 in the disclosed apparatus 300. The aperture 50(30) is a square shape area with 8x8 matrix of apertures extended both in azimuth and elevation directions, the resolution channel-3 maximum width and height is same as prime channel, The channel consists of a set of transparent and less transparent, each cell’s FOV is one eight of the total FOV in elevation and in azimuth direction. In the disclosed example of figure-4, the FOV cell D5 of column D and row 5 covers a FOV of 12.25 deg in azimuth and 12.25 deg in elevation. The resolution channel-3 is having total 64 FOV Cells, each quadrant of TFOV is again divided into four sub quadrants and these sub quadrants consists of four FOV cells and these four FOV cells will have four different transparency levels same as of resolution channel-1. Likewise in the case of resolution channel-2, when the collimated radiation incident on the apparatus 500, an encoded image of resolution channel-3 will be formed on the detector plane, wherein the detector 7030 is located centrally directly below the aperture 50(30). The encoded image on the detector plane 70 consists of a matrix of radiation with different intensity regions and encoded image will wander on the detector plane 70 based on the collimated radiation angle of incidence, the detector 7030 will give an output of certain value based on which intensity region of radiation moved on to the detector 7030. By comparing the signal amplitude of resolution channel-3 with the intensity amplitudes of prime channel and resolution channel-1&2, from which cell the radiation is transmitted can be assessed and intern the angle of arrival can be found. The wondering of shadow mask may be confined to within resolution channel-3 square area using four thin metal sheets placed on all the four sides of the resolution channel-3.
This method of encoded mask and detector can be extended to n- number of channels and the resolution depends on the FOV cell matrix in azimuth and elevation. This novel approach of finding the angle of arrival in both azimuth and elevation using same photodetectors will significantly reduce the number of radiation detectors required for finding the angular resolution compared with finding the resolution separately for azimuth and elevation.
Figure 6 illustrates an apparatus for the conversion of radiation sensor output current to optimum voltage signal, according to an exemplary implementation of the present disclosure. It consists of amplification and pulse shaping circuit. This figure represents optical to electrical conversion of collected radiation by photo detector, the conversion uses a high gain bandwidth operational amplifier for current to voltage conversion with a feedback resistor acting as an amplifier. A compensating capacitor in parallel to the gain resistor to serve the purpose of reducing gain peaking and bandwidth limiting is used. Followed by the optical to electrical conversion a pulse shaping circuit would expand the pulse so that its available for a longer duration, pulse shaping circuit is an operational amplifier with unity gain and pulse expansion R and C elements at output. The pulse shaping circuit also acts a low pass filter by reducing spurious noise pulses which may occur after optical to electrical conversion.
Figure 7 illustrates an apparatus for the conversion of optimum analogue voltage from different channel to equivalent digital signal, according to an exemplary implementation of the present disclosure. It consists of multiplexer, analogue to digital converter and a controller/FPGA to control these apparatuses. This figure represents the signal chain of selection and digital conversion, the shaped pulse signals will be processed by a high speed analog to digital converter preceded by a multiplexer for selection of respective optical to electrical conversion channel. The selection of channels is performed by a controller with programmable digital logic, the controller can also be microcomputer or a logic circuit or a high end processor, the controller selects respective channel to read the digital equivalent value of analog amplitude collected from current to voltage conversion circuitry shown in Figure 6. The number of channels required depends on resolution of interest, the multiplexer/multichannel ADC is accommodated with required number of input channels to resolve as per requirement.
Each radiation detector is a combination of two or more detectors with input attenuation filters, detectors with different attenuation factors would facilitate the system for dynamic range improvement.
An independent and always illuminated radiation detector termed as reference detector is used in this approach, the reference detector is similar to an angle resolving detector which can be single or combination of two or more detector with different attenuation factors to facilitate the system for dynamic range.
The prime detector is connected to a signal chain similar to that represented in Figure 1, the current to voltage converted signal from reference channel is given to ADC through Mux as shown in similar setup as figure 7.
Figure 8 illustrates a digital block for conversion of real-time digital signal from sensors to attenuation normalised signal for digital comparison, according to an exemplary implementation of the present disclosure. The Digital equivalent signal of prime channel is passed to a Digital Attenuator which generates attenuated digital equivalents of angle channels, the digital attenuator does the job of attenuation by a factor equivalent to attenuation factor used with resolution channels per angle resolver.
The digital output extracted from angle sensors after being passed through an analog to digital converter is then given to a digital case comparator which validates from which angle channel the signal would have come from. The output from each angle sensor amplitude is multiplied with reference channel output. This is to reduce the noise and amplify the signal. Multiplied signal output signal is compared with calibrated model of attenuation.
There will be a separate block for calculating transition angle. These are the angle at which radiation falls on intersection of different attenuation mask. This is done with the help of nearest approximation principle. By which whenever the relative amplitude value falls intermediate as compared to the attenuation a, b, c and d. The reference channel output are multiplied with different possible weightage combination for attenuation a, b, c and d to achieve nearest value as that of angle channel. This weightage value are used to identify the azimuth elevation angle.
Figure 9 illustrates a digital block for conversion of real-time digital attenuation normalised signal to 2bit noise compensated digital representation according to an exemplary implementation of the present disclosure. It consists of comparator and noise removed block. It also consists of digital block for faulty sensor identification. Faulty sensor detector block is used to identify non-working radiation sensor. This is achieved by comparing the digital output of each detector output with predetermined threshold over time. As the radiation sensor output will have some radiation exposure all the time and would not have full exposure all the time. Continuous different static value as relative to other sensor will help to identify these faulty sensors.
The noise removed block is used to avoid the noise input. The noise model for electronic circuit will be stored this subtracted from real-time signal. As already reference channel input is multiplied with angle channel. The output of this block will have less noise.
This is further processed to create binary out. As shown in the table. This done with the help of data base of threshold value for each attenuator and the resolution channel number. This because each resolution channel will have different attenuation factor due to mask characteristics.
Further the combination of output of faulty sensor identification along with transition angle correction and noise removal is used to achieve final corrected binary table as shown in table. Here each quadrant with attenuation A,B,C &D is represented by 2 bit binary .00,01,10,11, respectively.
The apparatus gives a digital code as the output for the determination of the angle of arrival of the incident collimated radiation, all the possible digital outputs of the apparatus is listed in table-2. As per the table-2, 2 bit digital coded word will give a definite information about the direction.
TABLE-1
Sr. No. RESOLUTION channel-1 RESOLUTION channel-2 RESOLUTION channel-3
1 00 00 00
2 00 00 01
3 00 00 11
4 00 00 10
5 00 01 00
6 00 01 01
7 00 01 11
8 00 01 10
9 00 11 00
10 00 11 01
11 00 11 11
12 00 11 10
13 00 10 00
14 00 10 01
15 00 10 11
16 00 10 10
17 01 00 00
18 01 00 01
19 01 00 11
20 01 00 10
21 01 01 00
22 01 01 01
23 01 01 11
24 01 01 10
25 01 11 00
26 01 11 01
27 01 11 11
28 01 11 10
29 01 10 00
30 01 10 01
31 01 10 11
32 01 10 10
33 11 00 00
34 11 00 01
35 11 00 11
36 11 00 10
37 11 01 00
38 11 01 01
39 11 01 11
40 11 01 10
41 11 11 00
42 11 11 01
43 11 11 11
44 11 11 10
45 11 10 00
46 11 10 01
47 11 10 11
48 11 10 10
49 10 00 00
50 10 00 01
51 10 00 11
52 10 00 10
53 10 01 00
54 10 01 01
55 10 01 11
56 10 01 10
57 10 11 00
58 10 11 01
59 10 11 11
60 10 11 10
61 10 10 00
62 10 10 01
63 10 10 11
64 10 10 10

In one of the exemplary implementation, a method and an apparatus for the detection and determination of angle of arrival of a collimated radiation for one direction and the same method is extended for both azimuth and elevation directions. The apparatus for the detection and determination of angle of arrival of a collimated radiation consist of diverse attenuated optical encoded mask and a radiation detector plane separated by a predefined distance, amplifier (602), pulse shaping circuit (604), multiplexer (702), analog to digital converter (704) and controller/FPGA/GPU (706). Here each radiation detector is combination of two sensors with low and high sensitivity. This is used to avoid saturation. When an optical radiation which is collimated falls on the apparatus containing the encoded mask and radiation detectors, the optical to electrical conversion happens Radiation detector is followed by amplifier followed by pulse shaping circuitry followed by multiplexer followed by an analogue to digital converter. This optical to digital conversion is fully controlled by a controller which control the optical to digital conversion resolution, channel selection and reference voltage selection.
In another exemplary implementation, the one direction method is expected to have multiple channels with prime channel which allow total radiation intensity to transmit without any change, and resolution channels which allow a different intensity transmission for different field of view sectors, the two dimensional method consists of a prime and resolution channels, the prime channel of two dimensional allow both azimuth and elevation coverage radiation without any change in the intensity, and resolution channel are divided into a FOV cells where each cell width is one fourth of the width of the previous cell. The resolution channel -1 cell width is one fourth of prime channel and resolution channel-2 cell width is one fourth of resolution channel-2. An apparatus with encoded mask and detector plane which are separated by a predetermined distance to maintain the FOV, the encoded mask is with dielectric coated apertures for implementation of the method that transmits different intensities of radiation through it as per the method. The encoded mask contains a prime channel with one sector in one direction and a cell in two directional case that transmits all the radiation, the resolution channels are divided into different sectors and cell as per the method that allow different intensities, when the collimated radiation incident on the apparatus image of the encoded mask forms on the detector plane, the image wanders on the detector plane as per the radiation angle of arrival, by comparing the detector signal of prime and resolution channel, the angle of arrival of the radiation can be determined with high angular accuracy.
In another exemplary implementation, the orientation between different resolution channel is optimised so that less number of bit transition occurs for minimum angular change. The digital signal is then processed to reduce the noise and faulty sensor identification. The controller updates the angle table on-the-fly based on attenuation normalisation and faulty sensor identification. The usage of mask weightage based angle calculation will reduce transition angle error. This error happens when the radiation falls between attenuation mask boundaries.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.
,CLAIMS:
1. An apparatus for detecting the angle of arrival of a collimated radiation beam, said apparatus comprising:
an attenuated optical encoded mask configured to receive the collimated radiation beam and modulate the beam based on its angle of incidence;
an amplifier (604) connected to the attenuated optical encoded mask, configured to amplify the modulated beam;
a pulse shaping circuit (604) connected to the amplifier (602), configured to shape the amplified signal into a predetermined waveform;
a multiplexer (702) connected to the pulse shaping circuit (604), configured to select and forward the shaped signal;
an analogue to digital converter (704) connected to the multiplexer (702), configured to convert the selected analogue signal into a digital signal; and
a processor selected from the group consisting of a microcontroller (706), a microprocessor, a Field Programmable Gate Array (FPGA), and a Graphics Processing Unit (GPU), connected to the analogue to digital converter, configured to compute the angle of arrival of the collimated radiation beam based on the digital signal with high angular accuracy for at least one directional axis, wherein the apparatus is configured to detect the angle of arrival in both one and two dimensional directions.

2. The apparatus as claimed in claim 1 further includes:
a plurality of prime channels configured to transmit a total radiation intensity without modification, wherein the prime channel covers a total field of view (FOV) in both azimuth and elevation directions and;
a plurality of resolution channels covering the total FOV, wherein each resolution channel is subdivided into distinct transparency sectors designed to modulate the relative radiation intensity, wherein each subdivided resolution channel further includes:
a first resolution channel divided into two sectors, each covering half of the FOV and allowing two distinct levels of radiation intensity;
a second resolution channel divided into four sectors, each covering a quarter of the FOV, and
a third resolution channel divided into eight sectors, each covering an eighth of the FOV, with each sector of the resolution channels permitting different levels of radiation intensity based on the transparency of that sector;
determining the angle of arrival in both azimuth and elevation directions by comparing the radiation intensity levels received through the resolution channels with those received through the prime channels, thereby achieving high angular accuracy in one directional axis.

3. The apparatus as claimed in claim 1 and claim 2, said apparatus further includes:
radiation detector plane which is positioned along with the optical encoded mask at a predefined distance from each other, wherein the optical encoded mask includes different dielectric coatings that establish various transparency sectors corresponding to the prime channels and the resolution channels;
the radiation detector plane is equipped with a plurality of radiation detectors, each radiation detector being associated with the respective prime channel or resolution channel to receive radiation transmitted through the optical encoded mask;
wherein upon incidence of the collimated radiation on the optical encoded mask, an image of the optical encoded mask is projected onto the radiation detector plane, such that when the radiation beam strikes the apparatus at varying angles, the image of the optical encoded mask shifts across the radiation detector plane, resulting in varying light intensity levels at different locations on the radiation detector plane corresponding to the prime channels and the resolution channels, the varying light intensity levels cause the generation of electrical signals of different intensities in the radiation detectors associated with the prime channels and the resolution channels; and
the angle of arrival of the collimated radiation beam is determined in both azimuth and elevation directions by comparing the electrical signal intensities corresponding to the resolution channels with the electrical signal intensity of the prime channel, thereby identifying through which sectors of the resolution channel the radiation has been transmitted and inferring the angle of arrival based on these intensity comparisons.

4. The apparatus as claimed in claim 1 further includes an analogue to digital converter (ADC) which is operatively coupled with a multiplexer (MUX), wherein this configuration effectively reduces the necessity for plurality of ADCs by enabling the MUX to selectively route signals from various channels through a single ADC.

5. The apparatus as claimed in claim 1 further includes:
a reference channel configured for thresholding, which enables the identification of a faulty sensor in real-time and allows the apparatus to maintain operational functionality with reduced resolution in the event of a sensor failure;
the analogue to digital converter (ADC) based relative thresholding utilizes input from the reference channel, and is configured to reduce the occurrence of false sensing by effectively mitigating the impact of background radiation on the sensor readings;
wherein the apparatus includes digital multiplication, wherein a calibrated reference channel is multiplied with the signal from the angle channel.

6. The apparatus as claimed in claim 1, said apparatus further includes a configuration that utilizes mask weightage for the calculation of angles, whereby the weightage assigned to different portions of the mask based on their resolution channel and orientation contributes to the determination of the angle of arrival of the collimated radiation beam.

7. The apparatus as claimed in claim 1, wherein the apparatus is equipped with both low gain and high gain sensors, this dual-gain configuration is designed to prevent sensor saturation by adjusting the sensitivity of the apparatus based on the intensity of the incoming radiation which enhances the dynamic range of the apparatus.

8. A method for detecting the angle of arrival of a collimated radiation beam, said method comprising:
receiving, by an attenuated optical encoded mask, the collimated radiation beam and modulate the beam based on its angle of incidence;
amplifying, by an amplifier (602) connected to the attenuated optical encoded mask, the modulated beam;
shaping, by a pulse shaping circuit (604) connected to the amplifier (602), the amplified signal into a predetermined waveform;
selecting and forwarding, by a multiplexer (702) connected to the pulse shaping circuit (604), the shaped signal;
converting, by an analogue to digital converter (704) connected to the multiplexer (702), the selected analogue signal into a digital signal; and
computing, by a processor selected from the group consisting of a microcontroller (706), a microprocessor, a Field Programmable Gate Array (FPGA), and a Graphics Processing Unit (GPU), connected to the analogue to digital converter, the angle of arrival of the collimated radiation beam based on the digital signal with high angular accuracy for at least one directional axis, wherein the apparatus is configured to detect the angle of arrival in both one and two dimensional directions.