Adaptive phase lighting system for synchronous celestial and terrestrial observations

Abstract

This application related to adaptive phase lighting system, which cancels the effect of sky-glow on the detection of terrestrial and celestial targets. It comprises a synchronization signal (26) radio transmitter (25), an adaptive modulated lighting phase receiver (12), and a synchronous optical detection receiver (12). The system permits the unification of outdoor lightings (10) phase to allow synchronous optical detection of faint target (18) berried in heavy light-pollution (17), protects astronomical observatories (21) from urban sprawl, helps terrestrial surveillance, earth satellites and airborne optical imaging device (22) to detect intruder targets under extreme sky-glow, and boosts homelands security.

Description

[0001] ADAPTIVE PHASE LIGHTING SYSTEM FOR SYNCHRONOUS CELESTIAL AND TERRESTRIAL OBSERVATIONS

[0002] FIELD OF INVENTION

[0003]

[0001] The present invention is an integrated electronic system for cancelling the effect of sky glow on electro-optical detectors.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] The glow level of natural unpolluted starry sky is usually less than 1.74 ped / m2or more commonly higher than 21.63 mag / arcsec2, which corresponds to very low effect of stray light on the observation and detection of both celestial faint objects (such as satellites, comets, planets, stars, nebulae, galaxies, quasars,..) and intruder terrestrial targets (such as stealth planes, missiles, camouflaged ground targets . . . ).

[0006]

[0003] But since the invention of white quantum lighting, the sky glow began to increase all over the world, obstructing the activities of astronomical observatories and limits the sensitivity of terrestrial surveillance satellites and air bom systems.

[0007]

[0004] The reason behind this phenomenon is the fact that modem outdoor lighting systems based on LED (light emitting diodes) technology, which extensively used in urban areas, emit a tremendous amount of short wavelength up light, that tends to increase sky glow several order of magnitude via Mie scattering.

[0008]

[0005] Urban sprawl towards astronomical observatories and starlight reserves may increase sky glow level to more than 3000 ped / m2or less than 14 mag / arcsec2, which reduces the number of visible stars in the hemisphere from 6000 to 5 only. It also decreases the limit of detectivity of terrestrial targets by satellites and airborne cameras.

[0009]

[0006] Many methods have been adopted to reduce sky glare, and consequently, its effect on celestial and terrestrial observations including; limiting the lighting angles to reduce up lights, reducing blue emissions in lighting spectmm, regulating lighting source operation time, prohibiting urbanization around observation cites for a distance between 10 to 30 km, using optical and digital filters to suppress background light in processing optical observations captured by astronomical and terrestrial cameras, and decreasing the amount of air pollution around the detection horizon.

[0010]

[0007] Most of the previously mentioned solutions for reducing sky glare seem to be inefficient in spite of their high cost, so that there is always a crucial need to redeploy astronomical observatories in remote sites far from urbanization.

[0011]

[0008] The present invention cancels the effect of urban lighting on the detection and observation of terrestrial and celestial target in presence of heavy sky glow, at a relatively low cost and high cutoff efficiency without need for redeploying both urban lighting and / or the observation facility.

[0012] SUMMARY OF THE INVENTION

[0013]

[0009] According to the present invention a novel category of electronic devices has been introduce to optoelectronics to unify the modulation phase of a huge number of urban light sources contributing in light pollution and causing sky glow, to enable heterodyne synchronous detection of faint celestial and terrestrial objects buried in heavy stray light by observation cameras.

[0014]

[0010] The present invention comprises three units including a synchronization signal radio transmitter, radio controlled adaptive phase light source modulator and a radio controlled synchronous camera trigger, forming between them a lock-in loop.

[0015] [Oi l] The role of the first unit is to generate and transmit a radio frequency signal, modulated by square wave synchronization signal of frequency fsin the order of 102Hz.

[0016]

[0012] While the role of second unit is to receive and demodulate the synchronization signal and use it to regulate the phase of a voltage controlled oscillator (VCO) in a phase locked loop where the center frequency f0equals fs, with an angular phase shift <psof n / 2. In the mean time f0modulates a power amplifier to force high power LEDs to emit amplitude modulated lighting having the same frequency and phase of f0prior to scattering on tropospheric aerosols and dust particles as an up light and causing sky glow.

[0017]

[0013] Similarly, the role of the third unit is to receive and demodulate the synchronization signal and use it to regulate the phase of a voltage controlled oscillator (VCO) in a phase locked loop where the center frequency f0equals fs, with an angular phase shift of n / 2. In the mean time f0signal is inverted so that the angular phase shift between the inverted trigger signal fDand fsincreases to 3n / 2 to trigger a detection camera with a frame rate that equals fssuch that it works only when the sky glow is minimum, and the detection of faint object is possible.

[0018]

[0014] It is possible to compensate the propagation delay 8 of both the synchronization signal and the sky glow by adding a variable phase shifter to the camera trigger output in the third unit.

[0019]

[0015] Knowing that c is the speed of electromagnetic waves in space and equals 108m / s, D is the distance between the first and the third unit, x is the horizontal distance between the first and the second unit, d is the horizontal distance between the second unit and the third unit, h is the maximum vertical altitude of the troposphere layer over the camera detector, and assuming that the maximum up-light total propagation distance till reaching the detection camera (which has the same position as the third unit) is the hypotenuse of a right angle triangle whose sides are d and h , which equals h2+ d2, it is possible to calculate 8 as the difference in propagation delays of both the sky glow and the synchronization signals, according to the relative position of the three units, from the expression:

[0020] 8 = TT+ TL- TD= - - - (1) where TTis the propagation delay in the tropospheric layer, TLis the propagation delay of the synchronization signal between the first and the second unit, and TDis the propagation delay of the synchronization signal between the first and the third unit.

[0021]

[0016] If h « 103m, d = 104km, d = 30 km, and D = x then 8 « 10-4s so that it represents an error of only 1% of the synchronization period which equals / i1= 10-2Hz, neglecting the propagation delay inside the hardware which is in the order of 10-12s.

[0022]

[0017] In case of long capture duration where detector camera is used in the photon counting mode, it is possible to merge the trigger signal to an optical shopper if digital shopper mode is note available.

[0023]

[0018] It is possible to use the first unit as a beacon with digital signature to provide a time / position coded signal, by adapting high speed digital PLL techniques in both the second and the third units.

[0024]

[0019] Equation 1 is valid in case of satellite and airborne camera assuming that, h is the minimum vertical altitude of the troposphere layer from the ground beneath the camera detector.

[0025]

[0020] The present invention can be deployed within a circle of radius 10-30 km from the astronomical observatory site, to suppress sky glow during camera observations to more than 106folds.

[0026] OBJECTIVES AND ADVANTAGES

[0027]

[0021] The present invention compromises between the need for urban lightings in sustaining nocturnal metropolitan activities, and the need for low sky glow to boost celestial and terrestrial observations.

[0022] By deploying the present invention with urban outdoor lightings it will be possible, to enable heterodyne synchronous detection of very faint celestial and terrestrial objects buried in heavy sky glow with a minimum stray light suppression ratio of 60 dB .

[0028]

[0023] The present invention enables normal operation of lighting sources, even at the absence of synchronization signal, and without any noticeable visible flickering.

[0029]

[0024] The present invention protects astronomical observatories from the light pollution caused by urban sprawl, and from being redeployed in another area, and consequently saves billions of money used for rebuilding.

[0030]

[0025] The present invention can be produced with extremely low budget so that the cost of one adaptive phase light source modulator unit is less than the cost the light bulb itself.

[0031]

[0026] The present invention assists earth satellite and airborne surveillance systems to perform detection and tracking of intruder terrestrial target buried in urban sky glow, to boost homelands security.

[0032]

[0027] The present invention can bring old astronomical observatories back to work, after being merged in urbanization, to retake advantage of their latitude and excellent location in celestial observations.

[0033]

[0028] The present invention helps countries with high light pollution levels to retaliate their astronomical activities.

[0034]

[0029] The invention can be used to assist airplanes to distinguish the runway lightings from urban lighting during approach prior to landing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035]

[0030] The present invention is explained more closely by means of different embodiments and with reference to the attached drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, the invention may admit to other equally effective embodiments.

[0036]

[0031] FIG. la illustrates the different elements contributing in an adaptive phase lighting system for synchronous celestial and terrestrial observations according to an embodiment of the present invention;

[0037]

[0032] FIG. lb illustrates the geometric modeling of an adaptive phase lighting system for synchronous celestial and terrestrial observations according to another embodiment of the present invention;

[0038]

[0033] FIG.2 illustrates the circuit block diagram of an adaptive phase lighting system for synchronous celestial and terrestrial observations according to another embodiment of the present invention;

[0039]

[0034] FIG.3a illustrates the time diagram representing the system output signals in absence of synchronization signal according to another embodiment of the present invention;

[0040]

[0035] FIG.3b illustrates the time diagram representing the system output signals in presence of synchronization signal according to another embodiment of the present invention;

[0041]

[0036] FIG.4 illustrates the global control loop of the system according to yet another embodiment of the present invention.

[0042]

[0037] Drawings reference numerals

[0043] 10 Outdoor LED lighting panel

[0044] 11 Street lighting pole

[0045] 12 Radio controlled adaptive phase light source modulator unit

[0046] 13 Useful light

[0047] 14 Light trespass (stray light)

[0048] 15 Up light (light pollution)

[0049] 16 Atmospheric aerosol and dust particles

[0050] 17 Sky glow (scattered light)

[0051] 18 Celestial object

[0052] 19 Celestial object light

[0053] 20 Observatory dome

[0054] 21 Telescope collector

[0055] 22 Telescope camera

[0056] 23 Radio controlled synchronous camera trigger

[0057] 24 Communication tower

[0058] 25 Synchronization signal radio transmitter unit

[0059] 26 Synchronization signal

[0060] 27 Satellite link

[0061] 28 Intrader target

[0062] 29 Intruder target light

[0063] 30 Earth satellite

[0064] 31 Earth satellite camera

[0065] 32 Satellite synchronous optical detection receiver

[0066] 33 Surveillance balloon

[0067] 34 Surveillance plane

[0068] 35 Radio transmitter

[0069] 36 Radio frequency modulator

[0070] 37 Digital buffer

[0071] 38 Frequency divider

[0072] 39 Crystal oscillator

[0073] 40 Radio frequency receiver

[0074] 41 Radio frequency demodulator

[0075] 42 Power amplifier

[0076] 43 Voltage controlled oscillator

[0077] 44 Loop filter

[0078] 45 Phase detector type II

[0079] 46 Exclusive OR gate phase detector type I 47 NOR gate lock detector

[0080] 48 LED lock-in indicator

[0081] 49 Inverting buffer phase shifter

[0082] 50 Programmable phase shifter

[0083] 51 Telescope camera field of view

[0084] 52 Camera monitor

[0085] S Difference in propagation delays between both the sky glow and the synchronization signals <psAngular phase shift of the synchronization signal

[0086] CW Continuous light wave from faint celestial object

[0087] D Horizontal distance from synchronization signal transmitter to detection camera d Horizontal distance from illumination source to detection camera h Maximum vertical altitude of the troposphere layer over the camera detector f0Phase locked loop central frequency fDCamera trigger frequency fLLighting modulation frequency fsSynchronization signal frequency x Horizontal distance from synchronization signal transmitter to illumination source

[0088] DETAILED DESCRIPTION OF THE INVENTION

[0089]

[0038] According to an embodiment of the present invention, figure la illustrates the physical elements contributing in the present invention where a transmission tower (24) is used for broadcasting a synchronization signal (26, 27) generated by a synchronization signal radio transmitter unit (25) to be received, by outdoor illumination poles (11) comprising an adaptive phase lighting source (10) modulator unit (12), by weather balloons (33), by reconnaissance planes (34), by surveillance satellites (30) carrying a synchronous optical detection receiver (32) controlling a camera (31) for the optical detection (29) of intruder objects (28), and by synchronous camera (22) trigger unit (23) as an imaging equipment of an optical telescope collector (21) inside an observatory dome (20) used for collecting the faint light (19) of a celestial object (18) berried in sky glow (17), scattered on tropospheric aerosols (16) from up light illuminations (15) and stray lights (13, 14). While figure lb illustrates the ground wave distances form transmission tower (25) to the receivers (12) and (23) denoted x and D, the ground distance from the lighting source (10) to the receiver (23) denoted d, the maximum vertical altitude of the troposphere layer over the camera detector (22) denoted h , and the up light (15) longest tropospheric scattering path from the lighting source (10) to the telescope collector (21) calculated as ( Vh2+ d2+ h).

[0090]

[0039] According to another embodiment of the present invention, figure 2 illustrates a simplified block diagram representing the electronic circuits used in each unit of the system, in which the first unit (25) comprises a crystal oscillator (39), a frequency divider (38), a digital buffer (37), a radio frequency modulator (36), and a radio transmitter (35). The second (12) and the third (23) units comprises a radio frequency receiver (40), a radio frequency demodulator (41), a digital buffer (37), a phase locked loop (PLL) built with a phase detector type II (45), a loop filter (44), and a voltage controlled oscillator (43) having a center frequency f0which equals to the synchronization signal frequency fsand connected to an in- lock built with an exclusive-or gate (46) , a Nor gate (47) and a LED lock-in indicator (48). The PLL output of the second unit (12) is driving a power amplifier (42) or a MOSFET chopper transistor to modulate a high power LED lighting source (10) with a frequency °f / i which equals fswith an angular phase difference of 7T / 2, while The PLL output of the third unit (23) is driving an inverting buffer (49) and a programmable phase shifter (50) to trigger a telescope camera (22) with a frequency of fDwhich equals fswith an angular phase difference of 3TT / 2 SO that the camera (22) captures the faint light (19) of the celestial object (18) during the period in which the LED lighting is off.

[0091]

[0040] According to another embodiment of the present invention, figure 3a illustrates the time diagram representing the system output signals, in absence of synchronization signal fswhere the phase angles of f0, fDand fswhich are completely random and the effect of sky glow (17) is altering the observation (51) of a faint (19) celestial object (18), while figure 3b illustrates the time diagram representing the system output signals, in presence of synchronization signal fswhere the phase angles of f0, fDand fsare synchronized and the effect of sky glow (17) is suppressed.

[0092]

[0041] According to yet another embodiment of the present invention, figure 4 illustrates the global control loop of the lock-in detection method used to suppress the effect of sky glow (17) on the telescope camera (22), where the synchronization signal (26), controls the adaptive modulated lighting phase receiver (12), and a synchronous optical detection receiver (23), to provide unification of outdoor lightings (10) phase, to allow synchronous optical detection of faint target (18) berried in heavy light-pollution (17).

[0093] SUMMARY, RAMIFICATION AND SCOPE

[0094]

[0066] From the preceding illustration, it will be seen that the described invention is a layout of an adaptive phase lighting system, which cancels the effect of sky glow on the detection of terrestrial and celestial targets. It comprises three units including a synchronization signal radio transmitter, radio controlled adaptive phase light source modulator and a radio controlled synchronous camera trigger, forming between them a lock-in loop. The present invention compromises between the need for urban lightings in sustaining nocturnal metropolitan activities, and the need for low sky glow to boost celestial and terrestrial observations at via low cost solution, which protects astronomical observatories from urban sprawl and saves billions of money used for rebuilding, and helps terrestrial surveillance, earth satellites and airborne optical imaging device to detect intruder targets under extreme sky glow to boost homelands security. Basing on the previous description, the scope of the invention shall not be limited on the given design example that is subject of changes by skilled artisans, but rather on the scientific methodology behind this embodiment.

Claims

CLAIMSWhat is claimed is:

1. An adaptive phase lighting system for synchronous celestial and terrestrial observations, said adaptive phase lighting system comprising: a remote synchronization signal transmitter with a standard modulation frequency oscillator, a carrier modulator and a high power transmitter providing long range broadcasting and coverage, a plurality of remotely controlled adaptive phase light source modulators with a carrier receiver, a carrier demodulator, a digital phase locked loop and a power amplifier driving a plurality of quantum and / or thermal urban light sources to provide modulated illumination, a remotely controlled synchronous camera trigger with a carrier receiver, a carrier demodulator, a digital phase locked loop, a phase inverter and a programmable phase shifter providing synchronous trigger / shopper signal to an observation camera, wherein said remote synchronization signal transmitter controls both the phase angle of said remotely controlled adaptive phase light source modulators and the phase angle of said remotely controlled synchronous camera trigger / shopper to perform synchronous observations for very faint celestial and / or terrestrial objects berried in said modulated stray light by said observation camera.

2. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein the lighting modulation depth is one hundred percent whereby square wave in the sub kilo Hertz frequency range, providing normal visual illumination profile with no flickers and / or dimming for the indoor and / or outdoor urban lightings3. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein the angular phase shift between said modulated lightings and said trigger / shopper camera and / or detector signal is a hundred and eighty degrees out of phase such that said camera and / or detector is active during the dark period of said modulated illumination.

4. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein the propagation delay of said synchronization signal and both said modulated lighting signal and said camera trigger / shopper signal is negligible with respect to said synchronization signal period.

5. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein said synchronization signal is transmitted through radio frequency, and / or microwave, and / or laser, and or optical fiber links whereby any type of carrier modulation techniques.

6. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein said synchronization signal frequency is within the frequency response of said quantum and / or thermal lighting source providing said full depth of modulation.

7. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein the maximum frame rate of said camera is less or equal to said synchronization signal frequency.

8. An adaptive phase lighting system for synchronous celestial and terrestrial observations according to claim 1 wherein the absence of said synchronization signal does not disturb normal operation of said lighting sources.

9. The method of unifying said modulation phase of a plurality urban lighting sources contributing in light pollution and causing sky glow, to enable homodyne and / or heterodyne synchronous detection of said faint celestial and / or terrestrial objects buried in said modulated stray light by said observation earner as / detectors .

10. The use adaptive phase lighting system for synchronous celestial and terrestrial observations in any application or under any modification whereby changing the type of communication link, the nature of transmission media, the frequency and / or the waveform and / or the protocol of synchronization signal, the electronic processing technology, the nature of the photo-detector, the nature of the target, or whereby appending or omitting or replacing one or more consisting part of said adaptive phase lighting system.

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