IMPROVEMENTS IN AND RELATING TO LASER DESIGNATOR PODS (LDP)

Abstract

A Laser Designator Pod (LDP) protective system, the LDP protective system comprising: a protective hood a laser detector arranged within the protective hood to generate a signal when exposed to laser radiation within a predefined range of wavelengths; and a computing device to record the generated signal.

Claims

1. A Laser Designator Pod (LDP) protective system, the LDP protective system comprising: a protective hood; a laser detector arranged within the protective hood to generate a signal when exposed to laser radiation within a predefined range of wavelengths; and, a computing device to record the generated signal.

2. The system of claim 1 wherein the laser detector and the computing device are physically separated, with the laser detector being arranged for use within the protective hood and the computing device being arranged for use outside the protective hood.

3. The system of claim 2 wherein the laser detector and the computing device are electrically connected by means of a cable.

4. The system of claim 1, wherein power is provided to the system by means of a portable battery pack, a mains to DC convertor, or Power over Ethernet, PoE.

5. The system of claim 1, wherein the laser detector is provided with an optical emitter (D1, D2) operable at a wavelength within the predefined range of wavelengths and arranged to function in a self-test mode.

6. The system of claim 5 wherein the laser detector is provided with a further optical emitter arranged to emit light at a wavelength outside the predefined range of wavelengths to indicate a power-on status of the system.

7. A Laser Designator Pod (LDP) comprising the system according to claim 1.

8. The LDP of claim 7 wherein the predefined range of wavelengths correspond with a range of wavelengths emitted by a laser in the LDP.

9. The LDP of claim 8, wherein the system is arranged to indicate that the laser in the LDP has fired and that the laser is operating within the predefined range of wavelengths.

10. The LDP of claim 7, wherein the system is configured to detect a plurality of predefined wavelength ranges, each of the plurality of predefined wavelength ranges corresponding to an operational mode of the LDP, each operational mode comprising a discreet range of predefined wavelengths.

11. The LDP of claim 10 wherein the predefined wavelength ranges correspond to three operational modes of the LDP, the operational modes comprising: a training mode comprising a predefined wavelength in the range of from 1200 to 1700 nm; a combat mode comprising a predefined wavelength in the range of from 800 to 1200 nm; and a marker mode comprising a predefined wavelength in the range of from 500 to 1100 nm.

12. The LDP according to claim 7, wherein the system is arranged for communication with a further computing device via a wired or wireless connection wherein the further computing device is arranged to execute a program to perform a test procedure on the LDP.

13. A method of detecting laser fire within a protective hood fitted over a Laser Designator Pod, LDP, using the system and/or LDP of claim and comprising the steps: providing the laser detector within the protective hood; performing a test on the LDP; detecting the presence of a fired laser within a predefined range of wavelengths; wherein the predefined range of wavelengths correspond with a range of wavelengths emitted by a laser in the LDP; generating a signal in response to the laser detector being exposed to laser radiation within the predefined range of wavelengths; and recording the generated signal using a computing device.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] Embodiments of the invention will now be described by way of example only with reference to the figures, in which:

[0045] FIGS. 1a and 1b show a prior art arrangement including an LDP and safety hood;

[0046] FIG. 2 shows a system according to an embodiment of the invention;

[0047] FIG. 3 shows a circuit schematic for the system of FIG. 2, according to an embodiment of the present invention; and

[0048] FIG. 4 shows a flowchart of a method according to an embodiment of the present invention.

DETAILED DESCRIPTION

[0049] FIG. 2 shows a system 100 according to an embodiment of the present invention. The system 100 is arranged to be partially installed inside the hood 10, and to communicate with an external computer to report any instances of laser firing within the hood.

[0050] FIG. 3 shows a circuit schematic of various features of the system 100 and both FIGS. 2 and 3 are referred to in the following description.

[0051] In more detail, the system 100 comprises a laser detector 110 which is arranged within the interior of the hood 10. The laser detector comprises an optical sensor D4, which is sensitive to laser radiation at a wavelength of transmission. Upon receipt of laser radiation at optical sensor D4, a voltage is presented at an input of integrated circuit U1 which is operable to create a 1 ms pulse which is transmitted via means of a cable 120 to a computing device 140, which is located outside the hood 10.

[0052] U1 is a monostable multivibrator (part number 74LVC1G123DP). When powered from a supply between 3.0V & 3.6V the shortest pulse that U1 is guaranteed to detect (across R4) is 3 ns. The duration of the electrical pulse generated by D4 across R4 is dependent on: [0053] i. The power of the light incident on the detector (More power=shorter light pulse required to trigger U1) [0054] ii. The duration of the incident light pulse [0055] iii. The wavelength of the incident light pulse (Shorter wavelength=longer light pulse required to trigger U1) [0056] iv. Circuit capacitance (higher capacitance=longer light pulse required to trigger U1) [0057] V. The resistance of R4 (Higher resistance=shorter light pulse required to trigger U1)

[0058] The optical detector D4 is a photodiode which is sensitive to wavelengths in the range of 500 nm to 1700 nm. If light from the laser, within this range of wavelengths, falls on the detector D4, then this causes a current to flow through resistor R4. This creates a voltage that is sensed by pin 2 of U1. If this voltage is greater than about 2V then U1 will output a single 3V3 pulse with a duration set by resistor R5 & capacitor C3 (approximately 1 ms). This pulse is used to set an interrupt to the computing device 140, which is described later.

[0059] The light falling on D4 must be removed, to a level where the voltage on U1 pin 2 is less than about 1V, and then re-applied in order to cause U1 to output another pulse. Thus, the computing device 140 is interrupted each time a new light pulse is detected. The software running on an external computer (not shown) connected to the computing device 140 can then measure the time between successive pulses to distinguish between the Marker and either the Combat or Training Lasers, which represent different operational modes of the LDP. If the Pulse Repetition Frequency, PRF, of the combat & training lasers are sufficiently different from each other, then the computing device 140 will be able to distinguish between them.

[0060] The laser detector 110 is connected, through the body of the hood 10, via a length of electrical cable 120, such as multi-connector ribbon cable, to the computing device 140, such as a Raspberry Pi. The computing device receives the 1 ms pulse generated by the laser detector 110 at a General Purpose Input/Output (GPIO) pin. Receipt of this pulse triggers a hardware interrupt which can be registered and processed by a further external computing device (not shown) which is connected to the computing device 140. The connection from the computing device 140 to the further external computer device may be effected by a further wired connection, such as Ethernet, fibre optic, or, where possible, via a wireless connection, such as Wi-Fi.

[0061] Power may be provided to the system 100 via a portable battery pack, a mains to DC convertor or Power over Ethernet (POE).

[0062] The further external computer device, which is arranged to run software associated with the ongoing testing of the LDP, is therefore alerted to the firing of the laser in the LDP, even though there is no physical access to the interior of the hood 10. Such a firing may be intentional or not, but the fact that it may be reliably detected and recorded allows an operator to take any corrective action which may be required. The corrective action may involve further tests and/or remedial action.

[0063] When the computing device, 140, GPIO output 16 is set high, then transistor Q1 will turn on and cause Infra-Red IR emitters D1 & D2 to illuminate. The light from D1 & D2 will then illuminate D4, simulating the laser light produced by the LDP. This will allow the computing device 140 software to perform a built-in test. D1 & D2 emit light with a wavelength between 900 nm & 1000 nm. These devices are eye safe and so there is no risk to personnel if these are used outside the confines of the hood 10.

[0064] D3 is a Power-On LED that emits in the visible spectrum. A blue LED is preferably used so that its spectrum (400 nm to 600 nm) is not detected by D4 and so does not interfere with the normal operation of the system 100. In one test set up, a visible-light camera which forms a part of the LDP is able to see the blue light, thus confirming power is being supplied to system 100.

[0065] In one embodiment, the laser detector 110 is fitted inside the hood 10 at the time of manufacture of the hood so that it is a truly integral part of the hood. Alternatively, the laser detector 110 may be retro-fitted to an existing hood 10.

[0066] The exact location of the laser detector 110 inside the hood is relatively unimportant, since the laser radiation typically reflects around and effectively illuminates the entire interior. As such, the laser detector can be located at any convenient location. Some trial and error may be required to find the optimum position. However, it is not necessary for the laser to be directly incident on the detector.

[0067] Since the LDP, when undergoing EMC testing, is located in a very delicate environment, from an EMC point of view, care is required in the design and manufacture of the system 100. As such, screened and wired connections are preferred over wireless links and battery power is preferred over mains power. Such steps can assist in avoiding additional possible sources of EM interference.

[0068] FIG. 4 shows a flowchart depicting the steps of a method 200 according to an embodiment of the present invention. At 202, a hood 10 is provided, which comprises a laser detector 110. The laser detector may be integrally formed with the hood or it may be retro-fitted at a later time.

[0069] At 204, the EMC test is performed on the LDP or aircraft. At 206, the computing device 140 continually monitors the laser detector to determine if a pulse signal is generated, which is indicative of a fired laser within the hood. As a part of the monitoring process, an operator is able to determine whether the test should be completed or terminated and whether any remedial action is required.

[0070] By means of an embodiment 100 as set out above, it is possible to monitor an interior space of a protective hood 10 fitted to an LDP 1 when undergoing testing, especially EMC testing. Such an arrangement permits reliable monitoring of laser activity, whether intentional or not, thereby ensuring that the LDP is operating within permitted limits.