JP2009139569A - Optical response device and optical response system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical response device and an optical response system that can avoid being tracked by a flying object having an infrared sensor. <P>SOLUTION: Provided is the optical response device comprising a laser generator which emits laser light wavelength-swept in the infrared range, a receiver which has sensitivity in the wavelength band wherein the wavelength sweeping is performed and detects the laser light emitted by the laser generator and reflected by a body to be detected, and an analyzer which analyzes a detection signal obtained by the receiver, the optical response device being characterized in that the analyzer analyzes a search wavelength where the intensity of the laser light reflected by the body to be detected decreases, and the laser generator emits the laser light fixed to the search wavelength toward the body to be detected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical response device and an optical response system.

  The radiation of high-temperature exhaust gas emitted from an aircraft such as a jet has a wavelength in the infrared band. For this reason, it is possible to track the flying object with a sensor having sensitivity in this wavelength band.

  If this sensor emits interfering light toward the sensor in a wavelength band having detection sensitivity, normal operation of the sensor becomes difficult and tracking from the flying object can be avoided.

  The infrared transmittance at the flight altitude depends on the wavelength, and the infrared band having a high transmittance is called an “atmosphere window”. Usually, a sensor for tracking a flying object is designed to have detection sensitivity in a narrow wavelength band within the band of the atmospheric window.

There is a technical disclosure example regarding a wavelength conversion laser device (Patent Document 1). In this technology disclosure example, the intensity ratio of at least two laser beams having different wavelengths output from the first-stage wavelength conversion optical system can be made variable. However, the wavelength of the laser light to be irradiated to obstruct the tracking from the flying object may be the search wavelength of the sensor provided in the flying object, and laser light of other wavelengths is unnecessary.
JP 2002-139757 A

  An optical response device and an optical response system capable of avoiding tracking from a flying object having an infrared sensor.

  According to one aspect of the present invention, a laser generator that emits laser light that has been wavelength-swept in the infrared band, and a sensitivity that is emitted in the wavelength band that is swept in the wavelength range, is emitted from the laser generator and A receiver for detecting the reflected laser beam; and an analyzer for analyzing the detection signal obtained by the receiver, wherein the analyzer reduces the intensity of the laser beam reflected by the detected object. An optical response device is provided in which the search wavelength is analyzed, and the laser generator emits laser light fixed to the search wavelength toward the detection target.

  Moreover, according to another aspect of the present invention, toward a flying body that tracks the moving body using a search wavelength in a wavelength band narrower than the wavelength band of infrared rays emitted from the exhaust gas of the moving body, A laser generator for emitting wavelength-swept laser light from the moving body, and an analyzer for estimating the search wavelength based on wavelength dependence of reflected light intensity of the laser light reflected by the flying body. An optical response system is provided, wherein laser light fixed to the estimated search wavelength is emitted from the laser generator toward the flying object, and tracking of the flying object can be obstructed. Is done.

  Provided are an optical response device and an optical response system capable of avoiding tracking from a flying object having an infrared sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual diagram for explaining an optical response system according to the present embodiment.
Aircraft 10 such as a jet emits hot exhaust gas 14. Radiation from the exhaust gas 14 has a wide infrared wavelength band corresponding to the temperature. The flying object (detected object) 30 includes a sensor 30a having light receiving sensitivity to the infrared ray 16 having a narrow wavelength band, and tracks the flying object (moving object) 10.

  On the other hand, the flying object 10 is equipped with a light response device 12. The optical response device 12 includes a laser generator 12a, a receiver 12b, and an analyzer 12c. The laser generator 12 a irradiates the flying object 30 with a pulsed laser beam 18 that can be swept in wavelength. The laser generator 12a will be described later.

  The receiver 12b is sensitive to the infrared wavelength band of the pulsed laser light 18 from the laser generator 12a, receives the reflected light 20 from the flying object 30, converts it into an electrical signal 13, and transmits it to the analyzer 12c. For the receiver 12b and the sensor 30a of the flying object 30, an infrared detection element using a semiconductor pn junction can be used. In this case, the cutoff wavelength of the infrared detection element is 1.1 μm for Si, 1.8 μm for Ge, 3 μm for PbS, and 7.7 μm for InSb. Further, it is possible to provide a solid-state imaging device in which infrared detection elements are arranged in a one-dimensional or two-dimensional array instead of a single element and are hybrid-connected to a Si CCD drive circuit to display an infrared intensity distribution.

  The analyzer 12c estimates the search wavelength of the sensor 30a of the flying object 30 based on the electrical signal 13, and transmits a control signal 15 for emitting the pulsed laser light 22 fixed to the same wavelength to the laser generator 12a. The analyzer 12c estimates the spatial position of the flying object 30 by reflected light analysis.

  The laser generator 12a emits pulsed laser light 22 having the same wavelength as the search wavelength of the sensor 30a toward the sensor 30a, thereby hindering normal operation of the sensor 30a.

  Note that if the reflected light from the pulsed laser light having a constant repetition frequency is subjected to frequency analysis, the flying object can be identified but the search wavelength cannot be identified. If the sensor is disturbed using a wavelength different from the search wavelength, the disturbing effect may be reduced or not disturbed. Compared with this, in the optical response device 12 and the optical response system according to the present embodiment, the search wavelength can be estimated, and therefore, the pulse laser beam 22 fixed to this wavelength can be irradiated and the normal operation of the sensor 30a can be disturbed. Therefore, it is not necessary to irradiate a pulsed laser beam, and it becomes easy to further enhance the interference effect.

FIG. 2 is a flowchart showing the response order of the optical response system according to the present embodiment.
FIG. 3 shows the wavelength dependence of the light intensity used in the optical response system. The vertical axis represents the relative light intensity, and the horizontal axis represents the relative wavelength. FIG. 3A is an example of the wavelength dependence of the infrared intensity of the exhaust gas 14 of the flying object 10 and has a wide infrared wavelength band.

  Since the sensor 30a included in the flying object 30 uses a band pass filter or the like, the light receiving sensitivity is often narrow in the search wavelength λ1 and the wavelength pass band Δλ as shown in FIG. As shown in FIG. 3C, the laser generator 12a scans and emits the pulsed laser light 18 into the space while sweeping the wavelength in the infrared wavelength band (S100).

  The pulse laser beam 18 is reflected by the flying object 30, and the pulse train of the reflected light 20 is incident on the receiver 12b (S102). The spatial position of the flying object 30 can be estimated by analyzing the electrical signal 13 from the receiver 12b (S104).

  Further, the analyzer 12c estimates the search wavelength λ1 at which the reflected light intensity decreases from the reflected light intensity wavelength dependency which is a pulse train (S106). The search wavelength λ1 shown in FIG. 3D indicates that the sensor 30a absorbs the pulsed laser light 18.

  Next, the laser generator 12a emits the pulsed laser light 22 having the same wavelength as the search wavelength λ1 toward the flying object 30 as shown in FIG. 3E by the control signal 15 from the analyzer 12c (S108). ). The optical response device 12 controls and emits the output of the pulse laser beam 22, the modulation method, the modulation waveform, the emission direction, etc., and interferes with the normal operation of the sensor 30a of the flying object 30. For example, if the output of the pulse laser beam 22 is made higher than the infrared intensity emitted from the flying object 10, the sensor 30a can be easily disturbed. When the detection element of the sensor 30a is a single element, the sensor 30a erroneously recognizes the traveling direction of the flying object 10 when the pulse modulation frequency is changed. Furthermore, when the detection element is an image pickup device, halation or the like occurs, making sensing difficult.

  If the normal operation of the sensor 30a is thus obstructed and tracking of the flying object 30 can be avoided, the irradiation of the pulsed laser light 22 is terminated. If tracking is continued, irradiation is continued (S110).

  When the light response device 12 is mounted on the flying object 10, the light response device 12 and the light response system according to the present embodiment obstruct the tracking of the flying object 30 such as a missile, and shoot down the flying object 10. I can be spared. Further, even when the optical response device 12 is mounted on a ship or a vehicle, the tracking of the flying object 30 can be similarly prevented.

  Next, the infrared wavelength band used in the above optical response system will be described. Infrared rays have a wavelength band in which absorption by water vapor or carbon dioxide is large in the atmosphere. FIG. 4 shows the wavelength dependency of the infrared transmittance. FIG. 4A shows the case where the altitude is 6 km from the ground, and FIG. 4B shows the case where the altitude is 1 km. The vertical axis represents infrared transmittance (%), and the horizontal axis represents wavelength (μm).

  Generally, the infrared wavelength band is 0.7 μm to 1 mm. In FIG. 4, the infrared transmittance is high in the vicinity of the bands having wavelengths of 2 to 2.4, 3.4 to 4.2, and 4.5 to 4.9 μm. This band is called an atmospheric window and can increase the light receiving sensitivity of the sensor 30a. Also, when used in an optical response system, optical loss can be reduced, so that attenuation of pulse laser light can be reduced and reception sensitivity can be increased.

  As shown in FIG. 4, the difference in infrared transmittance at altitudes of 1 km and 6 km is small, and it can be said that the windows of the atmosphere are substantially the same. For the sensor 30a of the flying object 30, a narrow wavelength band in the wavelength band of the atmospheric window is selected using a band-pass filter. This band is naturally unknown from the flying object 10, and the wavelength of the pulse laser beam 18 toward the flying object 30 needs to be swept widely within a possible range.

  FIG. 5 is a configuration diagram showing a specific configuration of the laser generator 12a in the optical response device 12 according to the present embodiment. The laser generator 12 a includes a seed light source 50, a fiber amplifier 70, a wavelength conversion unit 95, and a combining mirror unit 100, and emits pulsed laser beams 18 and 22 to the outside along the emission optical axis 65.

  First, the seed light can be obtained by exciting the YAG rod 53 with the LD excitation light source 51 or the like and generating stimulated emission by the Fabry-Perot resonator constituted by the mirrors 55 and 57. In addition, it is set as pulsed laser light using the Q switch 54 which consists of an AO (Acousto-Optic) element.

The obtained pulse laser beam is wavelength-converted by an OPO (Optical Parametric Oscillator) element 58 using a nonlinear crystal such as KTP (KTiOP ₄ ). That is, wavelength conversion is performed by dividing one high energy (high frequency) photon into two low energy photons in a nonlinear crystal arranged in an optical resonator formed by two mirrors. Signal light and idler light can be obtained from the excitation light. The wavelength (λs) of the signal light is shorter than the wavelength (λi) of the idler light. If the wavelength of the excitation light is λp, (Equation 1) holds between them.
1 / λp = (1 / λs) + (1 / λi) (Formula 1)

When the excitation light is an Nd: YAG laser and the wavelength λp is 1.064 μm, for example, λs = 1.9 μm and λi = 2.418 μm. A case where λs = λi = 2.128 μm is called degenerate OPO. The obtained pulse laser beam is wavelength-converted by an OPO element using a nonlinear crystal such as KTP (KTiOP ₄ ).

  Since the signal light and idler light emitted from the seed light source 50 are orthogonal to each other, they are polarized and separated by the polarizer 60. That is, idler light having a long wavelength is bent, further bent by the mirror 61, and emitted to the outside. On the other hand, short-wavelength signal light enters the fiber amplifier 70. Since the peak output of the seed light is low and long-distance transmission is difficult, it is preferably amplified by a fiber amplifier 70 using a thulium (Tm) -doped optical fiber 75 or the like. Also in this case, excitation light is incident from the LD excitation light sources 71a and 71b from both ends of the optical fiber 75 to excite Tm. Since the amplification gain band of Tm is wide, it is easy to obtain an amplified output even if the incident wavelength changes.

Even if the seed light is linearly polarized light, the amplified light becomes random polarized light including orthogonal components generated by transmission and amplification in the optical fiber 75. For this purpose, the laser light emitted from the fiber amplifier 70 is separated into a p-wave and an s-wave by a polarization separation mirror (or polarization beam splitter) 90 and is incident on the wavelength conversion unit 95 via the optical isolators 92 and 93. That is, the laser light from the fiber amplifier 70 emits signal light and idler light by the OPO elements 95a and 95b made of _two ZGP (ZnGeP ₂ ) provided in the horizontal and vertical directions.

  Further, when the direction of the optical crystal constituting the OPO element and the installation angle of the excitation light with respect to the optical axis are rotated in the direction determined by the optical crystal, λs and λi are continuously set while maintaining the relationship of (Equation 1). Wavelength sweep is possible by changing. For example, when the angle of the ZGP crystal is changed with respect to the optical axis of the wavelength light separated by the polarization separation mirror 90, the wavelengths in the 3 μm band and the 4 μm band can be swept.

  When emitting the pulsed laser light 22 having the search wavelength λ1 determined within the 3, 4 μm band, it is preferable to fix the angles of the two OPO elements 95a, 95b to emit the same wavelength. .

  The combining mirror unit 100 bends the laser beam from the OPO element 95a by the mirror M2, and bends the laser beam from the OPO element 95b by the mirror M1.

  The laser beam bent by the mirror M1 passes through the mirror M2, and is combined with the laser beam bent by the mirror M2 to become laser beams in the 3 μm band and the 4 μm band.

  The optical axis of the 3 μm and 4 μm band laser light in which the p wave and s wave are combined without waste is bent by the dichroic mirror M 3, and the 2 μm band laser light not passing through the fiber amplifier 70 is bent by the mirrors 62 and 63. Together with the optical axis thus obtained, it becomes the outgoing optical axis 65 of the laser generator 12a. The light that passes through the mirror M1 and enters the detector 101 is used as a time measurement start pulse when measuring the distance from the round-trip time of the light to an object such as the flying object 30a.

  Note that the required wavelength is often determined at 2 μm, and in this case, only the 3 and 4 μm bands are swept. Thus, if the use band of the search wavelength λ1 of the sensor 30a can be further limited, the wavelength sweep band can be further limited, and the laser generator 12a can have a simpler configuration.

  Since the pulsed laser light 22 emitted after estimating the search wavelength λ1 may be a fixed wavelength, it is not necessary to generate other wavelength light, and the output of the pulsed laser light 22 having the wavelength λ1 can be further increased to increase the effective interference distance. It becomes easy. Further, the operation of the optical response device 12 can be simplified.

  Further, the laser generator 12a illustrated in FIG. 5 sweeps the wavelength by the OPO element, makes the output high by the fiber amplifier 70, and makes the pulse laser output high by the Q switch 54. Since a solid optical material is used for this component, the optical response device 12 including the laser generator 12a can be easily downsized and easily mounted on an aircraft.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiment. Even if a person skilled in the art makes a design change with respect to the circuit, material, arrangement, size, shape, etc. of the laser generator, receiver, analyzer, and optical component constituting the optical response device, it deviates from the gist of the present invention. Unless otherwise included in the scope of the present invention.

Conceptual diagram of the optical response system of this embodiment Flow diagram showing the order of light response Graph showing the wavelength dependence of light intensity Graph showing the wavelength dependence of infrared absorptance Configuration diagram of the laser generator of the optical response device according to the present embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Aircraft, 12 Optical response device, 12a Laser generator, 12b Receiver, 12c Analyzer, 14 Exhaust gas, 16 Infrared, 18 pulse laser light, 20 Reflected light, 22 Pulse laser light, 30 Aircraft, 30a Sensor, 50 seed light source, 65 outgoing optical axis, 70 fiber amplifier, 90 polarization separation mirror, 95 wavelength conversion unit, 100 synthesis mirror unit, search wavelength λ1

Claims (8)

A laser generator that emits laser light that has been swept in the infrared band; and
A receiver having sensitivity in the wavelength band to be swept, and detecting laser light emitted from the laser generator and reflected by a detection object;
An analyzer for analyzing the detection signal obtained in the receiver;
With
The analyzer analyzes a search wavelength at which the intensity of the laser beam reflected by the detected object decreases,
The laser generator emits a laser beam fixed to the search wavelength toward the detected object. The laser generator includes a seed light source, and a wavelength conversion unit that converts emitted light from the seed light source,
The seed light source and the wavelength conversion unit include a nonlinear crystal element,
2. The optical response device according to claim 1, wherein the wavelength of the emitted light from the nonlinear crystal element can be swept by changing the angle of incident light to the nonlinear crystal element.   3. The optical response device according to claim 2, wherein the nonlinear crystal element performs optical parametric oscillation. The laser generator further includes a combining mirror unit,
The seed light source includes a first nonlinear crystal element, and emits a first signal light and a first idle light,
The wavelength conversion unit includes a second nonlinear element, and emits a second signal light and a second idle light,
4. The light according to claim 2, wherein the first idle light, the second signal light, and the second idle light can be emitted along an outgoing optical axis of the combining mirror unit. 5. Response device.   The optical response device according to claim 2, wherein the laser generator further includes a fiber amplifier provided between the seed light source and the wavelength conversion unit.   The laser generator further includes a polarization separation mirror provided between the fiber amplifier and the wavelength conversion unit, and the p-wave and the s-wave separated by the polarization separation mirror are wavelength-converted, and the synthesis is performed. 6. The optical response device according to claim 5, wherein the optical response device is synthesized by a mirror unit and emitted along the outgoing optical axis. Laser that emits wavelength-swept laser light from the moving body toward a flying body that tracks the moving body using a search wavelength in a wavelength band narrower than the wavelength band of infrared rays emitted from exhaust gas of the moving body A generator,
An analyzer for estimating the search wavelength based on the wavelength dependence of the reflected light intensity of the laser light reflected by the flying object;
With
An optical response system characterized in that a laser beam fixed to the estimated search wavelength is emitted from the laser generator toward the flying object so that tracking of the flying object can be disturbed.   The optical response system according to claim 7, wherein the reflected light intensity decreases in the vicinity of the search wavelength.

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