JP2001343220A - Apparatus and method for measuring window face distortion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an apparatus and a method for measuring a window face distortion in order for measuring and correcting a wavefront aberration because of the distortion generated by a pressure of a flight wind or a temperature difference to the window face set to an aircraft optical antenna or the like. SOLUTION: There are provided modulating means 2 for modulating a light intensity of light generated from each of light sources 1, a small aperture part 3 for emitting the light from spatially different positions, an optical system 4 for irradiating the light to the window face 11 to be measured, a condenser lens 5 for collecting the light affected by the distortion of the window face 11, detecting means 6a and 6b for detecting a light intensity of the collected light, demodulating means 7a and 7b for demodulating detected light intensity signals, a signal-operating means 8 for calculating a wavefront inclination and the wavefront aberration generated by the distortion of the window face 11 with the use of demodulation signals, a light propagation direction variable means 9 for changing an advance direction of the light, and a control means 10 for controlling the light propagation direction variable means 9 on the basis of the operated result by the signal-operating means 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for measuring window distortion, and more particularly, to an apparatus and a method for measuring window distortion of an optical antenna for spatial optical communication between an airborne laser radar and an aircraft.

[0002]

2. Description of the Related Art In recent years, techniques for transmitting and receiving laser light from within an aircraft to carry out optical communication between aircraft and to measure wind speed and distance from within the aircraft using a lightwave radar have been studied. An optical antenna for transmitting and receiving laser light is protected from wind, temperature difference, obstacles, and the like by a protective window. FIGS. 9 and 10 show Proc. SPIE Vol.
The example of the optical antenna described in p178-197 is shown. This is an antenna system that has been prototyped to perform spatial optical communication between aircraft at altitudes of 12 km and altitudes of 50 to 500 km.
In these figures, reference numeral 101 denotes an electronic system (system e).
electronics 102) GPS / INS 102, emergency hatch (aircraft hatch mounting structure), 1
04 is a bulkhead mounting surface, 1
05 is a turret assembly and 106 is a window.

[0003] The emergency hatch 103 at the bottom of the aircraft fuselage
An optical antenna system is installed in a dedicated small tower 105 attached to the, and light is transmitted and received through a window 106 having a diameter of 20 cm. When cruising over the sky, the window 106 is subject to shape distortion and a change in refractive index distribution due to pressure and temperature differences due to the flying wind. As a result, when light passes through the window 106, a difference in optical path length is caused depending on the passing position, and as a result, a wavefront aberration occurs. This wavefront aberration degrades the light-gathering characteristics and transmission characteristics, causing communication errors and measurement errors. Usually, it is considered that the shape of the window 106 is made to match the curvature of the outer wall of the fuselage so as not to impair the smooth flow of the wind. However, the shape distortion and the refractive index distribution of the window 106 change from moment to moment depending on the flight conditions and the surrounding weather environment. The pressure applied to the window 106 by the flight and the change in the refractive index of the window surface are described in Proc. SPIE vol. 3705, p266.
It is analyzed in detail by calculation in -275.

On the other hand, as an example in which the change in the optical path length due to the passage through the window is taken into consideration, there is a document Proc. SPIE vol. 3705, p221-226. The change was measured before operation, not from inside the cabin during operation of the optical antenna during cruising.

[0005]

In the above-mentioned conventional optical antenna, a wavefront aberration occurs when light passes through a window, but the wavefront aberration cannot be taken into consideration. There has been a problem that the light collection characteristics and the transmission characteristics are deteriorated, and a communication error and a measurement error occur.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and in the case of using an optical antenna or an image sensor mounted on an aircraft, the wavefront aberration generated when light passes through a window is reduced. It is an object of the present invention to obtain a window surface distortion measuring device and a measuring method capable of measuring from a window.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a window surface distortion measuring device for measuring the distortion of a window surface provided in an optical antenna for transmitting and receiving a laser beam. A plurality of light sources that generate light, a modulation unit that modulates the light intensity of light generated by each light source independently and at an arbitrary frequency, an emission unit that emits light from the light source from a spatially different position, and an emission unit. A first optical system that irradiates the emitted light to the window surface of the object to be measured, and a second optical system that collects light that is irradiated to the window surface by the first optical system and is affected by the distortion of the window surface System, detecting means for detecting the light intensity of the light collected by the second optical system, demodulating means for demodulating a light intensity signal output from the detecting means, and a demodulated signal output from the demodulating means. Wavefront tilt and wavefront caused by window distortion Calculating means for calculating the difference; light propagation direction changing means for changing the traveling direction of light emitted from the emission means and irradiated by the first optical system; and light propagation direction changing means based on the calculation result by the calculation means. This is a window distortion measuring device including a control unit for controlling.

The first optical system and the second optical system are shared.

Further, the apparatus further comprises an optical path separating means for spatially separating the condensing position of the condensed light condensed by the second optical system.

[0010] The emitting means has a plurality of small openings for emitting light from spatially different positions.

Further, small openings are distributed in the central part and the peripheral part.

Further, the end faces of the small openings are arranged on the same plane.

Further, the end face of the small opening in the center and the end face of the small opening in the peripheral part are arranged on different planes.

The light emitting means is constituted by an optical fiber, transmits light from a light source via the optical fiber, and emits light from a spatially different position using an end face of the optical fiber.

[0015] The emitting means is constituted by an optical lens array.

Further, the second optical system collects light transmitted through the window surface.

Further, the light source, the modulation means, the emission means, the first optical system, the second optical system, the detection means, the demodulation means, the arithmetic means, the light propagation direction changing means and the control means are housed in the same housing.

In addition, the emitting means and the first optical system are housed in the same housing, and the light source, the detecting means, the demodulating means and the calculating means are installed separately from the housing.

The second optical system collects the light reflected from the window surface.

Further, the small opening in the peripheral portion is set at a rotationally symmetric position.

Each light source has a different combination of wavelengths.

In the light from the light source, a wavelength that transmits the window surface to the center light and a wavelength that easily reflects the window surface to the peripheral light are used.

Further, the modulation means modulates by assigning a different frequency for each wavefront aberration.

Further, the modulation means modulates by assigning a different phase to each wavefront aberration.

The modulating means allocates and modulates a different signal sequence for each wavefront aberration.

The detecting means is constituted by a detector having a light shielding mask.

Further, there is further provided an optical fiber for converging light provided between the second optical system and the detecting means for transmitting the condensed light condensed by the second optical system to the detecting means. ing.

Further, an optical fiber connector is provided at an input portion of the optical fiber constituting the emission means and at an output portion of the optical fiber for condensing light.

Further, the detecting means is provided for the central portion and the peripheral portion.
It comprises a detector capable of detecting light intensity by separating two regions.

The detection area at the center is circular.

Further, the detection means is constituted by a detector having a detection area in a peripheral area.

Further, the calculating means performs a calculation of only a combination of the sum, difference and coefficient multiplication of the demodulated signals.

The second optical system comprises a Cassegrain reflection optical system.

Further, there is further provided a converging power varying means for changing the converging power of the second optical system.

Further, there is further provided a light-collecting power control means for controlling the light-collecting power varying means by using the calculation result of the calculating means as an error signal.

The condensing power varying means changes the condensing power by controlling the curvature of the primary mirror of the Cassegrain reflection optical system.

The second optical system comprises a liquid crystal lens.

The present invention also relates to a window distortion measuring method for measuring distortion of a window provided in an optical antenna for transmitting and receiving laser light, wherein the method generates a plurality of lights having arbitrary wavelengths. Generating a light, modulating the light intensity of the light independently and at an arbitrary frequency, emitting the light from a spatially different position, and irradiating the emitted light to a window surface of the object to be measured. One optical step, a second optical step of condensing the light that has been affected by the distortion of the window surface illuminated on the window surface, and a detection step of detecting the light intensity of the collected condensed light, A demodulating step of demodulating the light intensity signal obtained in the detecting step, a calculating step of calculating a wavefront tilt and a wavefront aberration generated by distortion of the window surface using the demodulated signal obtained in the demodulating step, and an emitting step A light propagation direction changing step of changing the traveling direction of light emitted and irradiated by the first optical step, and a control step of controlling the light traveling direction by the light propagation direction variable step based on a calculation result of the calculation step And a window surface distortion measuring method comprising:

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 The principle of operation of the method and apparatus for measuring window distortion and refractive index change according to the present invention will be described with reference to the embodiment shown in FIG. The measuring apparatus of the present invention comprises a plurality of probe light sources 1 having arbitrary wavelengths for generating probe light, and a probe light intensity modulation for independently and temporally modulating the light intensity of the probe light from each light source 1 at an arbitrary frequency. Means 2, a small opening 3 having a plurality of small openings for emitting probe light, a collimating optical system 4 for illuminating a window 11 to be measured with the probe light emitted from the small opening 3,
Condenser lens 5 for condensing light affected by the distortion of window 11
Light intensity detecting means 6a and 6b for detecting the light intensity of the light condensed by the condenser lens 5, light intensity demodulating means 7a and 7b for demodulating the detected light intensity signal, It comprises a signal calculation means 8 for performing a signal calculation, a light propagation direction changing means 9 for changing the traveling direction of light, and a control means 10 for controlling the light propagation direction changing means 9. The light intensity detecting means 6a is provided on the object side of the condensing point of the condensed light by the condensing lens 5, and the light intensity detecting means 6b is located on the image plane rather than the condensing point of the condensing light by the condensing lens 5. It is installed on the side.

Next, the operation will be described. The probe light generated by the light source 1 is emitted from a spatially different position through the small opening 3. The small openings 3 are formed, for example, in a disk shape. Here, as shown in FIG. 2, a plurality of small openings 3 a provided in the small openings 3 are distributed in a center portion and a peripheral portion. I have. The six small openings provided in the peripheral portion are installed at rotationally symmetric positions. The light emitted from the small aperture 3a is converted into parallel light by the collimating optical system 4, and then applied to the window 11. The traveling direction of the parallel light differs depending on the position of the small aperture to be emitted, and the light condensing position is also spatially separated.

In this embodiment, a case where light transmitted through the window 11 is condensed by the condensing lens 5 will be considered as an example.
The intensity of the condensed light is detected by light intensity detecting means 6a and 6b installed before and after the converging point.

When the window 11 is not deformed, the spatial intensity of the small opening 3 which is the exit end of the probe light is maintained at the light intensity at the light condensing point. A spot appears.

On the other hand, when the window 11 is distorted or the refractive index distribution changes, the optical path length changes depending on the position where the window 11 passes, and a wavefront aberration ΔW occurs. As a result, the position of the focused spot and the shape of the focused spot change.

For example, when a uniform pressure is applied to a circular window having a fixed outer peripheral portion and a deflection occurs, the wavefront aberration accompanying the change in the optical path length is approximately expressed by equation (1).

[0045]

(Equation 1)

Here, ΔP: pressure difference on axis, R: window radius, E: elastic modulus of window material, ν: Poisson's ratio, t: thickness of window, λ: wavelength of probe light is there. Further, ρ is a normalized radius of the window, and when ρ = 1, represents the outer peripheral portion. Actually, since the pressure difference ΔP is not a uniform distribution, a higher-order term for ρ in Expression (1) is added.

It is generally known that the wavefront aberration generated due to the change in the optical path length can be expanded into various aberration components by the Zernike polynomial of the equation (2). Here, θ is the angle of the propagating light beam in the circumferential direction.

[0048]

(Equation 2)

A1 is a translation of the wavefront in the optical axis direction, A2 and A3 are wavefront tilts, A4 is defocused, A5 and A6 are astigmatisms A7 and A8 are coma components. In the first embodiment, the aberrations from A2 to A4 will be considered.

When a wavefront tilt is generated by passing through the window surface,
The focused spot moves in parallel in the wavefront tilt direction. When the inclination angle is further small, the spatial arrangement of the spots and the spot shape are maintained. FIG. 3 shows how the spot moves on the light intensity detecting means 6a or 6b due to the wavefront inclination. Therefore, the inclination angle can be estimated by detecting the movement amount of the spot. For example, when the spot movement amount is Δx and the focal length of the condenser lens is F, the wavefront inclination angle α can be calculated by Expression (3).

[0051]

(Equation 3)

A case will be described in which, for example, a one-dimensional detector having a detection sensitivity inside a circle is used as the light intensity detection means 6a and 6b. The radius of the detection area is set so that each converging spot condenses just outside the detection area. When a wavefront tilt occurs due to window distortion, the detected light intensity changes.

By modulating each spot, the movement of the spot can be detected only from the point detection signal, whereby the tilt direction and the tilt amount can be estimated. The procedure will be described below.

The names of the spots at the periphery are Sa, Sb, Sc,
Sd, Se, and Sf. Now, the probe light corresponding to the spots Sa, Sb, Sf is modulated at the frequency f1, and the probe light corresponding to the spots Sc, Sd, Se is modulated at the frequency f1 having a phase difference of 180 degrees.
The detection signal is demodulated at the frequency f1. For example, a synchronous detection method is used as demodulation means. This is because after multiplying the detection signal by the local oscillation signal synchronized with the modulation frequency of the probe light intensity,
By performing integration and averaging, a frequency component responding to the modulation is extracted as a DC amplitude. When the phases of the probe light modulation signal and the demodulation signal are the same, a positive value is obtained. Value.

Accordingly, the spots Sa, Sb and Sf are demodulated in the same phase, the demodulated signals are positive, and the spots Sc, Sd and Se are in the opposite phase, and the demodulated signals are negative.

In the case where there is no wavefront inclination, as shown in FIG. 3 (a), the focused spot is located at the center-symmetric position, and the in-phase demodulation component and the anti-phase demodulation component have the same absolute value and opposite signs. The demodulated signal becomes zero.

When the wavefront is inclined in the + x direction, FIG.
As shown in (b), the entire spot moves to the right, and the in-phase component increases in the detection signal. As a result, a positive value is output as the demodulated signal. On the other hand, when tilting in the −x direction, FIG.
The demodulated signal has a negative value as shown in FIG. Therefore, the amount of tilt in the x direction can be estimated from the demodulated signal of frequency f1.

Similarly, when the probe light corresponding to the spots Sb and Sc is modulated at the frequency f2 and the probe light corresponding to the spots Se and Sf is modulated at the opposite phase of the frequency f2, the wavefront tilt amount in the y direction is determined by the frequency f2. It can be estimated from the demodulated signal.

Accordingly, the wavefront inclination in the x and y directions can be separately estimated from the two types of demodulated signals using the frequencies f1 and f2. Further, calibration characteristics can be obtained by plotting a demodulated signal value when a known angle change is applied to the probe light with the window 11 removed. Determining the wavefront tilt amount from the demodulated signal value with reference to this calibration characteristic enables quantitative measurement.

Further, the frequency f in the demodulating means 7a, 7b
The demodulated signal of 1, f2 is used as an error signal, and the light propagation direction changing means 9 and its control means 10 are operated so as to change the traveling direction of the wavefront so that the error signal becomes zero. Can be corrected.

After the wavefront tilt is corrected by the above procedure, the change in the wavefront curvature becomes dominant as an effect of the window distortion. When the curvature of the wavefront changes, defocus (A4 in equation (2)) or astigmatism (A5 and A6 in equation (2)) occurs as a wavefront aberration term. As a result, the shape of the spot spreads.

Further, the spread of the spot is different before and after the light condensing position. FIG. 4 shows the difference in the spread of the spot distribution. FIG. 4A shows the defocus A4, FIG. 4B shows the astigmatism A5, and FIG.
(c) shows the change of the spot shape before and after the focal point for each component of the astigmatism A6. For simplicity, only one spot is shown as a representative, but in the actual case, spots having the same shape are arranged in the same arrangement as the position of the small opening.

FIG. 5 shows the spread of the focused spot due to the defocus. In order to consider the difference in the spread of the spot before and after the focal point, the light intensity detecting means 6a and 6b are fixed at positions equidistant before and after the ideal focal position. 5 (a) and 5 (c) show the distribution of condensed spots in the light intensity detecting means 6a, and FIG. 5 (b).
(d) shows the distribution of the converging spots in the light intensity detecting means 6b.

In order to detect the defocus, first, the probe light corresponding to all the condensed spots Sa, Sb, Sc, Sd, Se, and Sf is modulated at the frequency f3. Next, the difference between the signal from the detector fixed before and after the focusing position, which is demodulated at the frequency f3, is obtained. When there is no defocus, the areas of the spots included in the detection areas of the detection means 6a and 6b are equal as shown in FIGS. As a result, the two demodulated signals from the demodulating means 7a and 7b become equal, and the difference signal becomes zero. When the defocus occurs, the area of the spot included in the detection area changes as shown in FIGS. As a result, the values of the two demodulated signals are different, and the demodulated signals increase in proportion to the shift amount. The change in the direction of defocus appears as a change in the sign of the difference signal.

Next, a case where an astigmatism component exists will be described. FIG. 6A shows the distribution of condensed spots in the light intensity detecting means 6a when the astigmatism component A5 exists, and FIG. 6B shows the distribution of condensed spots in the light intensity detecting means 6b. Focus spot S to detect astigmatism component A5
Modulate the probe light corresponding to a, Sc, Sf at frequency f4,
In addition, the probe light corresponding to the converging spots Sb, Sd, and Se is subjected to opposite-phase modulation at a frequency f4. When the astigmatism A5 does not exist, the three spots on each detecting unit are circular as shown in FIGS. 6C and 6D, and the spot areas included in the detection areas are equal. Therefore, the difference between the two demodulated signals is zero. On the other hand, when the astigmatism A5 is present, the difference between the two demodulated signals is A5 because the spot areas included in the detection areas of the two detection means are different as shown in FIGS. Increases or decreases in proportion to

FIG. 7A shows the distribution of condensed spots in the light intensity detecting means 6a when the astigmatism component A6 exists, and FIG. 7B shows the distribution of condensed spots in the light intensity detecting means 6b. . Focus spot to detect astigmatism component A6
The probe light corresponding to Sb, Se is modulated at frequency f5. When the astigmatism A6 does not exist, the two spots on each detecting means are circular as shown in FIGS. 7C and 7D, and the spot areas included in the detection areas are equal. Therefore, the difference between the two demodulated signals is zero. On the other hand, when the astigmatism A6 exists, the difference between the two demodulated signals is A6 because the spot areas included in the detection areas of the two detection means are different as shown in FIGS. 7 (a) and 7 (b). Increases or decreases in proportion to

Therefore, the defocus A4, the astigmatism A5, and the astigmatism A6 are separated by the difference between the demodulation frequencies f3, f4, and f5.
Each aberration amount can be estimated.

Further, the demodulated signal can be calibrated using a window whose aberration amount is known in advance as a measurement object. By using this calibration characteristic, the amount of wavefront aberration accompanying the change in the curvature of the window can be quantitatively measured. Further, the signal operation means may be an operation of only the sum, difference, and coefficient multiplication of the demodulated signals.

When a condensing power varying means for changing the condensing power and a means for controlling the condensing power varying means are added to the condensing lens 5 of the first embodiment, the window distortion Can be used as an error signal to correct wavefront aberration due to window distortion.

In the first embodiment, as the light intensity detecting means, a detecting means having a detecting sensitivity inside the center circle is used. However, the detecting sensitivity does not exist in the center circular area but only in the peripheral orbicular zone. Even when the detection means is used, the window distortion can be measured in the same procedure. In this case, the inner radius of the annular zone is set to be slightly larger than the distance from the center to the condensing position of each spot, and each spot is set to be above the edge of the annular zone. Further, in this case, the sign of the demodulated signal with respect to the wavefront inclination is opposite to the sign shown in FIG.

As the light intensity detecting means 6a and 6b, the case where the central circular region is the detection region and the case where the central circular region has no detection sensitivity and the peripheral ring region is the detection region are described above. However, in order to realize each detection region, a light-shielding mask may be placed in front of the detection region to shield the periphery and the center from light.

Further, a light intensity detecting means which has both the inside of the circle and the circumferential portion as the detection area and which can separate and detect signals from the two areas may be used. In this case, the influence of the intensity variation of the condensed spot can be compensated for by providing a detection area outside the circle and taking the ratio between the demodulated signal and the demodulated signal in the circle inside detection area.

In the first embodiment, as an example of the probe light modulating means for measuring the amount of wavefront aberration due to the distortion of the window and the like, different frequencies are assigned to the respective wavefront aberrations for modulation, but the present invention is not limited to this case. Instead, a different phase may be assigned for each wavefront aberration and modulated, or a different signal sequence may be assigned and modulated for each wavefront aberration. It may be assigned and modulated.

An optical lens array may be used as the small opening 3.

In the plurality of light sources 1 having arbitrary wavelengths, each light source may have a different combination of wavelengths.

Embodiment 2 FIG. 8 shows an example in which the present invention is applied to an optical antenna as a second embodiment. In this embodiment, window distortion is measured using reflection of probe light from a window, an optical fiber is used as an output end of probe light, and an optical fiber is used as an incident end of collected light. It is a feature.

This measuring apparatus comprises a probe light source 21, a probe light intensity modulating means 22, an optical fiber 23 for outgoing light,
Collimating / condensing lens 24, optical path separating means 25, optical fiber 26 for condensed light, optical fiber connector 32, light intensity detecting means 27, light intensity demodulating means 28, signal calculating means 2
9, a light propagation direction changing means 30, a means 31 for controlling the changing means 30, and an optical communication / laser radar transceiver 33. In the drawing, the window 20 to be measured is also shown.

As an arrangement of the optical fiber 23 for the outgoing light, it is assumed that a fiber core is arranged at the small opening position (FIG. 2) of the first embodiment, for example, but the peripheral fibers may be arranged symmetrically. As long as it is not 6 points, it may be.

In the optical fiber 23, the peripheral fiber is used for emitting the probe light, but the central fiber can be used for purposes other than the probe light. In the second embodiment, it is assumed that a connection is made to the transceiver 33 of the optical communication / laser radar.

The probe light emitted from the optical fiber 23 is converted into parallel light by the collimating / condensing lens 24, and is converted into parallel light.
It is irradiated to 0. The probe light reflected by the window 20 passes through the collimating / collecting lens 24 again and is collected.

Here, the wavelength of the light to be emitted is determined by using a wavelength that easily transmits through the window 20 as the light emitted from the center and a wavelength that is easily reflected by the window 20 as the light emitted from the periphery. It is possible to achieve both the securing of the signal level and the reduction of the loss of light for optical communication / laser radar.

When window distortion or refractive index change occurs as in the first embodiment, a wavefront aberration occurs in the reflected probe light. The influence of the wavefront aberration appears as a movement of the converging spot with respect to a change in the wavefront inclination, and as a spread of the converging spot with respect to a change in the wavefront curvature.

In the same manner as in the first embodiment, the measurement and correction of the wavefront aberration caused by the window distortion can be performed.

In the second embodiment, the connection between the optical fiber 23 and the probe light source 21 and the transceiver 33 of the optical communication / laser radar, and the optical fiber 26
An optical fiber connector 32 is used to connect the light intensity detecting means 22 to the optical fiber.

In the first embodiment, the small opening 3
Although the end faces of “a” are arranged on the same plane as shown in FIG. 2, the present invention is not limited to this, and the small opening end face of the central part and the small opening end face of the peripheral part may be arranged on different planes. In the second embodiment, since the optical fiber 23 is used, the small opening end face at the center and the small opening end face at the peripheral part can be easily arranged on different planes.

In the second embodiment, it is assumed that all components necessary for window distortion measurement other than the window 20 and the transmitter / receiver 33 of the optical communication / laser radar are housed in the same housing. . However, the optical fiber connector 32 described above allows the output light optical fiber 23, the collimating / condensing lens 24, the optical path separating means 25, the condensing light optical fiber 26, the light propagation direction changing means 30, and the changing means 30 to be connected. The controlling means 31 is housed in the same housing, and the probe light source 21, the light intensity detecting means 30, the transceiver 32 of the optical communication / laser radar, the light intensity demodulating means 28, and the signal calculating means 29 are located at remote positions. Can be installed. As a result, the probe light source 21, the light intensity detecting means 30, and the transceiver 33 of the optical communication / laser radar are independently adjusted, repaired,
Replacement is possible, which has the effect of improving reliability and maintainability.

In the second embodiment, the description is made assuming that a refraction type lens is used as the collimating / condensing lens 24. However, the collimating and condensing functions are performed by using a Cassegrain reflection optical system or a liquid crystal lens. Any optical system that satisfies the condition may be used.

When a Cassegrain reflecting optical system is used, a means for controlling the curvature of the primary mirror of the Cassegrain reflecting optical system may be added. Thereby, the condensing power can be changed.

By using the signal obtained by the signal operation means 29 as an error signal and controlling the condensing power by means for controlling the curvature of the primary mirror of the Cassegrain reflection optical system, the change in the wavefront curvature caused by the window distortion is obtained. Can be corrected.

[0090]

According to the present invention, there is provided a window surface distortion measuring device for measuring the distortion of a window surface provided in an optical antenna for transmitting and receiving a laser beam. A plurality of light sources that generate light, a modulation unit that modulates the light intensity of light generated by each light source independently and at an arbitrary frequency, an emission unit that emits light from the light source from a spatially different position, and an emission unit. A first optical system that irradiates the emitted light to the window surface of the object to be measured, and a second optical system that collects light that is irradiated to the window surface by the first optical system and is affected by the distortion of the window surface System, detecting means for detecting the light intensity of the light collected by the second optical system, demodulating means for demodulating a light intensity signal output from the detecting means, and a demodulated signal output from the demodulating means. Wavefront tilt and wavefront yield caused by window distortion Calculating means for calculating the light propagation direction, changing the traveling direction of the light emitted from the emitting means and irradiated by the first optical system, and controlling the light propagation direction changing means based on the calculation result by the calculating means. And a control means for controlling the window surface distortion, the laser light of an optical antenna provided in an aircraft or the like, when passing through the window surface, due to the distortion of the window surface due to the pressure and temperature difference due to the flying wind. The generated wavefront aberration is measured from the inside of the device, the wavefront aberration is corrected, and a communication error, a measurement error, and the like due to a distortion of a window surface of the optical antenna can be prevented.

Further, since the first optical system and the second optical system are shared, the size of the apparatus can be reduced and the manufacturing cost can be reduced.

Further, since the apparatus further comprises an optical path separating means for spatially separating the light condensing position of the condensed light condensed by the second optical system, the light is converged at a plurality of spatially separated positions. Light can be emitted, and the accuracy of strain measurement can be increased.

Further, since the emitting means has a plurality of small openings for emitting light from spatially different positions, light can be emitted from spatially different positions with a simple configuration.

Further, since the small apertures are distributed in the central portion and the peripheral portion, the wavefront tilt and the wavefront aberration can be easily measured depending on the position and shape of the condensed spot.

Further, since the end faces of the small aperture are arranged on the same plane, the converging points coincide with each other, which facilitates the measurement.

Further, since the end face of the small opening at the center and the end face of the small opening at the peripheral portion are arranged on different planes, the degree of freedom of the configuration of the apparatus can be increased.

Also, since the light emitting means is constituted by an optical fiber, the light from the light source is transmitted through the optical fiber, and the light is emitted from a spatially different position using the end face of the optical fiber. It is possible to easily realize emission from a desired position.

Further, since the light emitting means is constituted by an optical lens array, light can be easily emitted from a desired position.

Further, since the second optical system condenses the light transmitted through the window surface, it is possible to more accurately measure the influence caused by the distortion when the laser light is transmitted under the same conditions. .

Further, the light source, the modulation means, the emission means, the first optical system, the second optical system, the detection means, the demodulation means, the arithmetic means, the light propagation direction changing means and the control means are housed in the same housing. Therefore, installation of the device is easy.

Also, since the emitting means and the first optical system are housed in the same housing, and the light source, the detecting means, the demodulating means and the calculating means are installed separately from the housing, the components in the housing are provided. , Repair and replacement can be performed independently, and reliability and maintainability can be improved.

Further, since the second optical system condenses the light reflected from the window surface, the first optical system and the second optical system can be shared, and the size of the apparatus can be reduced.

Further, since the small opening in the peripheral portion is set at the rotationally symmetric position, the wavefront tilt and the wavefront aberration in the x and y directions can be separately measured.

Also, since each light source has a different combination of wavelengths, it is possible to use light from each light source for different purposes depending on the wavelength.

Further, of the light from the light source, the wavelength that transmits the window surface as the central light and the wavelength that easily reflects at the window surface are used as the peripheral light, so that the signal level for measuring the window distortion can be secured. It is possible to achieve both reduction in loss of light for optical communication / laser radar.

Further, since the modulating means modulates by assigning a different frequency for each wavefront aberration, it is possible to easily distinguish the condensed spot.

Further, since the modulating means assigns and modulates a different phase for each wavefront aberration, the condensed spot can be easily distinguished.

Further, since the modulating means allocates and modulates a different signal sequence for each wavefront aberration, the condensed spot can be easily distinguished.

Further, since the detecting means is constituted by a detector having a light shielding mask, a desired detection area can be easily and accurately realized.

Further, there is further provided a condensed light optical fiber provided between the second optical system and the detecting means for transmitting the condensed light condensed by the second optical system to the detecting means. Therefore, light can be transmitted reliably and at a high speed.

Further, since the optical fiber connectors are provided at the input portion of the optical fiber and the output portion of the optical fiber for condensing light which constitute the emission means, each means is housed in one housing. Instead, the predetermined means can be installed at a position away from the housing.

Further, the detecting means is provided for the central part and the peripheral part.
It consists of a detector that can detect light intensity by separating two areas, so that a signal demodulated by providing a detection area outside the circle and a signal demodulated by the detection area inside the circle By taking the ratio, it is possible to compensate for the influence of the intensity variation of the condensed spot.

Since the detection area at the center is circular, the detection result at the center of the circle is used, so that the distortion of the window surface can be measured accurately.

Further, since the detection means is constituted by a detector having a detection area in the peripheral area, the distortion of the window surface is measured from the detection result at the peripheral contour, so that the amount of calculation can be reduced. Can be planned.

Further, since the arithmetic means performs only the combination of the sum, difference and coefficient multiplication of the demodulated signals, the processing time of the arithmetic operation can be reduced.

Since the second optical system is composed of a Cassegrain reflection optical system, it can perform two functions of collimation and light collection.

Further, since the apparatus further includes a condensing power varying means for changing the condensing power of the second optical system, the condensing power can be varied, and the convenience is improved.

Further, since the apparatus further includes a light-collecting power control means for controlling the light-collecting power varying means using an operation result of the calculating means as an error signal, a desired light-collecting power can be obtained.

Further, the condensing power can be easily changed by controlling the curvature of the primary mirror of the Cassegrain reflecting optical system by the condensing power varying means.

Further, since the second optical system is composed of a liquid crystal lens, it can perform two functions of collimation and light collection.

The present invention also relates to a window distortion measuring method for measuring the distortion of a window provided in an optical antenna for transmitting and receiving laser light, wherein the method generates a plurality of lights having arbitrary wavelengths. Generating a light, modulating the light intensity of the light independently and at an arbitrary frequency, emitting the light from a spatially different position, and irradiating the emitted light to a window surface of the object to be measured. One optical step, a second optical step of condensing the light that has been affected by the distortion of the window surface irradiated to the window surface, and a detection step of detecting the light intensity of the collected condensed light, A demodulation step of demodulating the light intensity signal obtained in the detection step, a calculation step of calculating a wavefront tilt and a wavefront aberration generated by distortion of the window surface using the demodulation signal obtained in the demodulation step, and an emission step A light propagation direction changing step of changing a traveling direction of light emitted and irradiated by the first optical step, and a control step of controlling a light traveling direction by the light propagation direction variable step based on a calculation result of the calculation step The wavefront generated by the distortion of the window surface due to the pressure and temperature difference due to the flying wind when the laser light of the optical antenna provided on the aircraft etc. passes through the window surface Measure the aberration from inside the aircraft,
Wavefront aberration can be corrected, and communication errors and measurement errors due to distortion of the window surface of the optical antenna can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a window distortion measuring device according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a position of a small aperture for emitting probe light according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing movement of a condensed spot due to a wavefront inclination.

FIG. 4 is an explanatory diagram showing a spread of a condensed spot due to a change in curvature of a wavefront.

FIG. 5 is an explanatory diagram of a spread of a condensed spot on a light intensity detection surface due to a defocus A4 component.

FIG. 6 is an explanatory diagram of a spread of a condensed spot on a light intensity detection surface due to an astigmatism A5 component.

FIG. 7 is an explanatory diagram of a spread of a condensed spot on a light intensity detection surface due to an astigmatism A6 component.

FIG. 8 is a block diagram showing a configuration of a window surface distortion measuring device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing an example of a conventional optical antenna system for mounting on an aircraft.

FIG. 10 is a diagram illustrating an example of a conventional optical antenna system mounted on an aircraft.

[Explanation of symbols]

1 probe light source, 2 probe light intensity modulation means, 3
Small aperture for probe light emission, 4 collimating optics,
5 Condensing lens, 6a, 6b Light intensity detecting means, 7a, 7b
Light intensity demodulation means, 8 signal calculation means, 9 light propagation direction variable means, 10 light propagation direction variable means 9 control means,
11 window surface, 20 window surface, 21 probe light source, 22
Probe light intensity modulating means, 23 Optical fiber for outgoing light, 24 Collimating / condensing lens, 25 Optical path separating means, 26 Optical fiber for condensing light, 27 Light intensity detecting means, 28 Light intensity demodulating means, 29 Signal operation Means, 30
Light propagation direction changing means, means for controlling the light propagation direction changing means, 32 optical fiber connector, 33 optical communication / laser radar transceiver.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA49 BB01 BB22 CC21 DD11 FF41 HH01 HH03 HH04 LL02 LL04 QQ13 2H051 BA49 BA53 BA72 5J084 AB20 AC04 AD03 BA05 BB02 BB31 EA04 EA31

Claims (32)

[Claims] 1. A window surface distortion measuring device for measuring distortion of a window surface provided in an optical antenna for transmitting and receiving laser light, comprising: a plurality of light sources for generating distortion measuring light having an arbitrary wavelength. A light source; a modulating means for modulating the light intensity of the light generated by each of the light sources independently and at an arbitrary frequency; a light emitting means for emitting the light from the light source from a spatially different position; A first optical system for irradiating the window surface of the object to be measured with the light emitted from the light source, and a light beam irradiated on the window surface by the first optical system and affected by the distortion of the window surface. A second optical system that emits light, a detection unit that detects the light intensity of the condensed light collected by the second optical system, and a demodulation unit that demodulates a light intensity signal output from the detection unit, Using the demodulated signal output from the demodulation means Calculating means for calculating a wavefront tilt and a wavefront aberration generated by the distortion of the window surface; light propagation direction changing means for changing a traveling direction of the light emitted from the emission means and irradiated by the first optical system; And a control means for controlling the light propagation direction changing means based on a calculation result by the calculation means. 2. The window distortion measuring apparatus according to claim 1, wherein the first optical system and the second optical system are shared. 3. The apparatus according to claim 1, further comprising an optical path separating unit for spatially separating a condensing position of the condensed light condensed by the second optical system. Window distortion measurement device. 4. The window distortion according to claim 1, wherein the emission means has a plurality of small openings for emitting the light from spatially different positions. measuring device. 5. The window distortion measuring device according to claim 4, wherein said small openings are distributed in a central portion and a peripheral portion. 6. The window distortion measuring apparatus according to claim 4, wherein end faces of the small openings are arranged on the same plane. 7. The window distortion measuring apparatus according to claim 5, wherein an end face of the small opening in the central portion and an end face of the small opening in the peripheral portion are arranged on different planes. 8. The light emitting means comprises an optical fiber, transmits the light from the light source through the optical fiber, and transmits the light from a spatially different position by using an end face of the optical fiber. 2. The light is emitted.
4. The window distortion measuring device according to any one of claims 3 to 3. 9. The window distortion measuring apparatus according to claim 1, wherein said emission means is constituted by an optical lens array. 10. The window distortion measuring device according to claim 1, wherein the second optical system collects light transmitted through the window surface. 11. The light source, the modulating means, the emitting means, the first optical system, the second optical system, the detecting means, the demodulating means, the calculating means, the light propagation direction varying means, and 11. The window distortion measuring device according to claim 1, wherein the control means is housed in the same housing. 12. The light source, the detection means, the demodulation means, and the arithmetic means are provided separately from the housing, while the light emitting means and the first optical system are housed in the same housing. The window distortion measuring device according to any one of claims 1 to 10, wherein: 13. The window distortion measuring device according to claim 1, wherein the second optical system collects light reflected by the window surface. 14. The window distortion measuring device according to claim 5, wherein the small opening in the peripheral portion is set at a rotationally symmetric position. 15. The window distortion measuring apparatus according to claim 1, wherein each of said light sources has a combination of wavelengths different from each other. 16. The light source according to claim 1, wherein, of the light from the light source, a wavelength that transmits through the window surface is used as central light, and a wavelength that is easily reflected by the window surface is used as peripheral light. The window distortion measuring device according to any one of the above. 17. The apparatus according to claim 1, wherein the modulating means modulates by assigning a different frequency to each wavefront aberration.
17. The window distortion measuring device according to any one of claims 16 to 16. 18. The window distortion measuring apparatus according to claim 1, wherein the modulating means modulates by assigning a different phase to each wavefront aberration. 19. The window distortion measuring apparatus according to claim 1, wherein the modulating means allocates and modulates a different signal sequence for each wavefront aberration. 20. The window distortion measuring apparatus according to claim 1, wherein said detecting means comprises a detector having a light shielding mask. 21. Condensed light for light which is provided between the second optical system and the detecting means and which transmits the condensed light condensed by the second optical system to the detecting means. 21. The device according to claim 1, further comprising a fiber.
The window distortion measuring device according to any one of the above. 22. The window according to claim 21, wherein an optical fiber connector is provided at an input portion of the optical fiber and an output portion of the optical fiber for condensing light constituting the emission means. Strain measuring device. 23. The apparatus according to claim 1, wherein said detecting means comprises a detector capable of detecting light intensity by separating two regions of a central portion and a peripheral portion. 23. The window distortion measuring device according to any one of 22. 24. The window distortion measuring apparatus according to claim 23, wherein the central detection area is circular. 25. The window distortion measuring apparatus according to claim 1, wherein said detecting means comprises a detector having a detection area in a peripheral area. 26. The arithmetic means, comprising: a sum of the demodulated signals;
26. The window distortion measuring apparatus according to claim 1, wherein only a combination of the difference and the coefficient multiplication is calculated. 27. The window distortion measuring apparatus according to claim 1, wherein said second optical system comprises a Cassegrain reflection optical system. 28. The window distortion measuring apparatus according to claim 1, further comprising a converging power varying means for changing the converging power of the second optical system. 29. The apparatus according to claim 2, further comprising condensing power control means for controlling said condensing power variable means using an operation result of said operation means as an error signal.
8. The window distortion measuring device according to 8. 30. The light-collecting power varying means changes the light-collecting power by controlling the curvature of a primary mirror of the Cassegrain reflection optical system.
The window distortion measuring device as described in the above. 31. The window distortion measuring apparatus according to claim 1, wherein the second optical system comprises a liquid crystal lens. 32. A window distortion measuring method for measuring distortion of a window provided in an optical antenna for transmitting and receiving laser light, comprising: generating a plurality of lights for measuring distortion having an arbitrary wavelength. A light generating step of causing the light to be emitted, a modulation step of modulating the light intensity of the light independently and at an arbitrary frequency, an emission step of emitting the light from a spatially different position, and the window surface of the object to be measured A first optical step of irradiating the light on the window surface, and a second optical step of condensing light that has been affected by the distortion of the window surface by irradiating the window surface; and A detecting step of detecting; a demodulating step of demodulating the light intensity signal obtained by the detecting step; and a wavefront tilt and a wavefront aberration generated by distortion of the window surface using the demodulated signal obtained by the demodulating step. A calculating step of calculating; a light propagation direction changing step of changing a traveling direction of the light emitted in the emission step and irradiated by the first optical step; and the light propagation direction based on a calculation result of the calculation step. Controlling a traveling direction of the light by a variable step.