JP6256876B2 - Accelerometer and active vibration isolator using the same - Google Patents

Description

  An extremely accurate atomic clock is realized by stabilizing the frequency of light from the light emitting element to the transition frequency of atoms. At this time, a light source that outputs a clock laser beam whose spectral line width is extremely narrow is used, but this may be configured using an external optical resonator. The external resonator is known to be affected by vibration from the installed environment. The present invention relates to an acceleration sensor using a plurality of optical resonators provided in a common spacer, and an active vibration isolator using the same, in order to suppress the influence of the vibration by negative feedback control of the vibration acceleration. .

As a laser light source having a narrow spectral line width, the following method is known.
(1) As shown in FIG. 8A, a laser beam from a laser oscillator whose length can be adjusted by a piezo element is converted into a Fabry-Perot optical interferometer whose length can be adjusted by a piezo element. Through wavelength scanning with a Fabry-Perot optical interferometer, light detection is performed in synchronization with the scanning, and the piezoelectric element of the optical resonator is controlled by PID (Proportional Integral Derivative) control with the detected light intensity. A laser source that locks to the top of the transmission spectrum of a Fabry-Perot interferometer.
(2) As shown in FIG. 8B, laser light from a laser oscillator whose length can be adjusted by a piezo element is passed through a reference Fabry-Perot optical interferometer. A laser light source that locks on the slope of the transmission spectrum of the Fabry-Perot optical interferometer to be referred to by adjusting the length of the optical resonator with an absorption signal.
(3) As shown in FIG. 8C, the light from a laser oscillator whose oscillation wavelength can be controlled by voltage is phase-modulated and input to a reference Fabry-Perot interferometer, and the reflected light is phase-modulated. By feeding back the signal obtained by synchronous detection with the signal and controlling the oscillation wavelength of the laser oscillator, the oscillation wavelength can be locked to the transmission spectrum of the Fabry-Perot optical interferometer to be referenced. This is known as the PDH method (Pound-Drever-Hall method).
(4) If there is a laser light source with a sufficiently stable output light wavelength and a laser light with a stable wavelength can be used, the laser light is shifted to a wavelength shifter that shifts with the output of a VCO (voltage controlled oscillator). By inputting, any laser oscillator with the above wavelength can be used instead.

  Non-Patent Document 2 describes an overall view of the Sr clock laser stabilization system shown in FIG. In the clock laser shown in FIG. 3 of Non-Patent Document 1, first, a laser beam having a relatively stable wavelength is generated in the pre-stabilization resonator portion by the PDH method using a diode laser. The wavelength of the laser light is slightly changed by a wavelength shifter (AOM in FIG. 3) and input to the ULE resonator. This ULE resonator is a Fabry-Perot resonator of a ULE spacer, and exhibits a characteristic that the resonance wavelength is very stable as described above. In addition, this ULE resonator has a very high finesse F and a very narrow transmission spectrum. The wavelength shifter adjusts the laser light stabilized by the pre-stabilization resonator using the wavelength shifter so as to match the transmission spectrum of the ULE resonator. This adjustment is based on the PDH method. As a feedback signal, a voltage or current corresponding to a deviation between the laser beam and the stabilized laser beam becomes the feedback signal. For example, this feedback signal is converted into a change in frequency by a VCO (voltage controlled oscillator) whose oscillation frequency changes according to the voltage, and is applied to the wavelength shifter. By this feedback loop, it is possible to obtain clock laser light locked to the transmission spectrum of the ULE resonator.

  The optical resonator is a key component for creating a local optical oscillator having no frequency fluctuation with the stable resonator length as a reference (reference).

It is known that ULE (Ultra-Low-Expansion, Corning) glass is desirable as a spacer material for a Fabry-Perot optical interferometer. This is because, as described in Non-Patent Document 1, the thermal expansion coefficient of ULE glass is about 10 ⁻⁸ / K, and the creep is as small as 0.2 to 0.5 × 10 ⁻¹⁵ / s. is there. One ULE glass member is conventionally provided with one optical resonator.

  As described above, ULE glass has a relatively small thermal expansion coefficient and creep value. However, in general, in order to achieve the stability required for an atomic clock, temperature management in units of millikelvin is required.

  In general, since the resonator length changes due to ground vibration transmitted from a point supporting the resonator, vibration from a vacuum pump, or the like, vibration isolation performance is extremely important. Usually, the above-mentioned clock laser is installed on a large vibration isolation table and becomes a large-scale device as a whole, and there is a problem in portability at present. Therefore, for the purpose of improving portability, it is desired to eliminate the vibration isolation table itself or at least to use a simple vibration isolation table.

  More specifically, for example, a vibration isolation table is used to suppress the influence of ground vibration. Generally, the vibration isolation table has a resonance frequency, and the vibration isolation performance is exhibited from this resonance frequency. On the high frequency side. For example, in a commercially available vibration isolation table having a footprint size of about 1 m × 1 m used for optical frequency standard applications, the lowest resonance frequency is 0.5 Hz. For example, the ground vibration is affected by a wave hitting the coast and has a peak of amplitude in a frequency region with a period of several seconds or more, and the amplitude is extremely small, but the ground reaching the support point of the resonator is described above. It is very difficult to suppress the influence of vibration. For this reason, usually, the shape of the resonator is devised so that the resonator length does not change even if the supporting point vibrates, and the influence is reduced.

  The vibration isolator can be classified into a passive vibration isolator and an active vibration isolator. In general, the former uses a large mass platform (or stage), and the latter uses a small mass platform. In this classification, the present invention belongs to an active vibration isolator.

  In general, even with an active vibration isolator, in the case of a table top size, it is difficult to create an acceleration sensor that is sensitive to vibration in the 0.1 Hz region that reaches the resonator. As described above, the reason why it is difficult to create an accelerometer having sensitivity in a low frequency range is that there is no so-called “non-moving reference” necessary for distinguishing very slow vibration as vibration.

  As a conventional acceleration sensor using an optical resonator, for example, Patent Document 1 (US Patent Application Publication No. 2013/0327146) is disclosed. In this disclosure, one reflector of an optical resonator is moved by a spring, and the change in the resonance frequency of the optical resonator is measured when acceleration is applied to the resonator, and the change in the resonance frequency is measured. Thus, the acceleration applied to the resonator is detected. However, the present invention uses a structure different from this.

  In addition, the optical resonator itself has been devised to be insensitive to vibration. In Non-Patent Document 3, there is a hollow mirror at the center of the optical resonator spacer, and one high-reflectance plane mirror and one spherical mirror at both ends. A vibration insensitive optical resonator is described in which the connected optical resonator is supported laterally by a mount. This vibration insensitive optical resonator is made into a vibration insensitive type by optimizing the mounting position of the mount. Non-Patent Document 4 describes an example in which the wavelength of output light from a diode laser is stabilized using an optical resonator in which an optical resonator is vertically mounted.

  As an example of a clock laser light generator, FIG. 3 of Non-Patent Document 2 shows an overall view of an Sr clock laser stabilization system. In the clock laser shown in FIG. 3 of Non-Patent Document 1, first, a laser beam having a relatively stable wavelength is generated in the pre-stabilization resonator portion by the PDH method using a diode laser. The wavelength of the laser light is slightly changed by a wavelength shifter (AOM in FIG. 3) and input to the ULE resonator. This ULE resonator is a Fabry-Perot resonator of a ULE spacer, and exhibits a characteristic that the resonance wavelength is very stable as described above. In addition, this ULE resonator has a very high finesse F and a very narrow transmission spectrum. The wavelength shifter adjusts the laser light stabilized by the pre-stabilization resonator using the wavelength shifter so as to match the transmission spectrum of the ULE resonator. This adjustment is based on the PDH method. As a feedback signal, a voltage or current corresponding to a deviation between the laser beam and the stabilized laser beam becomes the feedback signal. For example, this feedback signal is converted into a change in frequency by a VCO (voltage controlled oscillator) whose oscillation frequency changes according to the voltage, and is applied to the wavelength shifter. By this feedback loop, it is possible to obtain clock laser light locked to the transmission spectrum of the ULE resonator.

US Patent Application Publication No. 2013/0327146 US Patent Application Publication No. 2008/0271533

"Development of a 1Hz linewidth laser for optical lattice clocks", AIST Metrology Standard Report Vol. 7, No. 1 March 2008, pages 11-24 "3-3 Strontium Optical Lattice Clock", National Institute of Information and Communications Technology Quarterly 135-144 Vol.56 Nos.3 / 4 2010 S. A. Webster, M. Oxnorrow, and P. Gill, Phys. Rev. A 75, 011701 (R) (2007) A. D. Ludlow, X. Huang, M. Notcutt, M. Zanon-Willette, S. M. Foreman, M. M. Boyd, and J. Ye, Opt. Lett. 32, 641 (2007)

  It is known that a light source that outputs a clock laser beam constituted by using an external optical resonator is affected by vibration from an installed environment. The present invention realizes an acceleration sensor using a plurality of optical resonators provided in a common spacer in order to suppress the influence of the vibration, and further, using the acceleration sensor, the influence is negatively fed back to the vibration acceleration. An active vibration isolator that is suppressed by control is realized.

  In the acceleration sensor of the present invention, in addition to the main resonant optical path provided at the center of the spacer of the optical resonator, a plurality of optical paths are arranged at the eccentric position of the spacer, and the relative values of the resonant frequencies of these resonators The characteristic is that the fluctuation of the reflection reflects the vibration that has reached the resonator. In this case, the above-mentioned “non-moving reference” is the optical resonator itself, and the fluctuation of the relative value is obtained by differential detection. Therefore, common components such as the fluctuation of the resonator length due to the temperature change are canceled out. Furthermore, if a crystalline material such as a silicon single crystal is used as a material for the resonator spacer, unlike the case of glass, there is little aging drift of the resonator length, and the frequency component in the ultra-low frequency region is reduced. , Vibration sensitivity can be further increased to a low frequency range. Further, as a negative feedback, this resonator is installed on a movable piezo stage or the like, and the piezo stage is driven so that vibration detected as a change in the relative value is suppressed. This enables active vibration isolation. In this case, since the acceleration sensor is the resonator itself, there is no need to worry about a phase delay or the like in the transfer function from the sensor that tends to occur generally to the optical resonator length.

For this reason, the present invention is a plurality of optical resonators provided in a common spacer in an acceleration sensor that can detect vibrations reaching the resonator,
An acceleration sensor that detects the acceleration by measuring a change in the resonance frequency of a Fabry-Perot optical resonator using a laser beam,
A composite optical resonator comprising a plurality of optical resonators;
Acceleration deriving means for deriving acceleration applied to the composite optical resonator from at least two comparisons of the resonance frequencies of the plurality of optical resonators,
The composite resonator is a composite optical resonator including cavities for three or more optical resonators using a spacer having a rotational symmetry with respect to a center line as a common spacer,
Each of the cavities is parallel to each other,
One of the cavities is provided at a position including the center line, and the other cavity is provided at a position not including the center line and a symmetric position with respect to the center line.

The composite optical resonator is provided with an optical path in the direction of gravity,
Supported at a support point in the support provided on the outer periphery of the common spacer,
Each of the support points is provided at a position equidistant from the center line on an equidistant surface from any two of the cavities provided at a position not including the center line.

  By using a single crystal for the spacer material, an optical resonator in which secular change in resonance frequency is suppressed can be configured.

The number of the optical resonators and the number of the support points provided at positions not including the center line are 3 respectively.
The optical resonators are sequentially designated as A, B, and C, and the support points on the opposite sides of the center lines of A, B, and C are the support points A, B, and C, and the support points A, B, and C are When the Cartesian coordinates on the plane including the xy coordinates,
The acceleration deriving means derives an acceleration in the y direction from a difference between respective resonance frequency shifts from the optical resonator provided at a position including the center lines of B and C, and an x direction acceleration as the center of the A. This is derived from the resonance frequency shift from the optical resonator provided at the position including the line.

In addition, regarding the xy coordinates,
The acceleration in the x direction is determined from the average of the resonance frequency shift from the optical resonator provided at the position including the center line of B and C from the optical resonator provided at the position including the center line of A. This is obtained by subtracting the resonance frequency shift.

  Resonance frequency shifts of A, B, and C are incident on the optical resonators A, B, and C, respectively, and the laser beams locked to the optical resonators provided at positions including the center line. The deviation of the respective resonant frequency of A, B and C from the frequency.

Further, the present invention is an active vibration isolation device using an acceleration sensor by a plurality of optical resonators provided in a common spacer,
A driven table on which the composite optical resonator is mounted;
A drive system for driving the driven table so as to move on the surface;
A negative feedback circuit that applies negative feedback by applying the output of the acceleration deriving means to the drive system,
The negative feedback suppresses the output of the acceleration detecting means.

  The present invention solves the problem that it has been difficult to eliminate the influence of ground vibration of 1 Hz or less in an optical resonator. At present, an optical resonator of the 10 16th level is realized with a stability of 1 second, and further improvement of the vibration isolation performance is required for further improvement. Conventionally, it has been difficult to distinguish the aging effect of resonator materials in the low range from the change in resonator length due to vibration, but the aging effect is reduced by using a single crystal material as a resonator. Therefore, the present invention solves this point. Further, even in a portable or satellite-mounted local optical frequency oscillator in which it is difficult to use a heavy vibration isolation table, vibration isolation performance can be provided by using the present invention. In addition, in the ultimate optical resonator operated at extremely low temperatures, a prescription for the vibration of the refrigerator is required. The present invention is also effective as vibration isolation for the refrigerator vibration.

FIG. 2 is a block diagram showing an example of a stabilized light source 100 that is part of the configuration example of the present invention and that has stabilized the wavelength by locking the oscillation wavelength of the laser light source 101 to the resonance wavelength of the optical resonator 105. FIG. 3 is a block diagram of a stabilized light source 200 that is wavelength-stabilized by locking to the resonance wavelength of an optical resonator 205 when laser light 201 is input instead of the laser light source 101 of the stabilized light source 100. It is a schematic diagram which shows the optical resonator which comprises the acceleration sensor by the some optical resonator provided in the common spacer of this invention. It is a block diagram which shows the structural example of the acceleration sensor by the some optical resonator provided in the common spacer. It is a block diagram which shows the structural example of an acceleration sensor. The active vibration isolator using the acceleration sensor by the several optical resonator provided in the common spacer shows the structural example of the system which drives a vibration isolator, (a) Front view, (b) Plan view, (C) is a drive voltage generator. The active vibration isolator using the acceleration sensor by the several optical resonator provided in the common spacer shows the structural example of the system which drives the housing | casing of a composite optical resonator, (a) Front view, (b) Plane It is a figure and (c) is a drive voltage generator. It is a figure which shows the example of a laser light source of the narrow spectrum line width of a conventional system. (A) adjusts the length of the optical resonator with a piezo element, (b) locks to the slope of the transmission spectrum of the Fabry-Perot optical interferometer to be referenced, (c) shows the PDH method (Pound -Drever-Hall method). It is a figure which shows the conventional Sr clock laser stabilization system whole figure.

  Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, devices having the same function or similar functions are denoted by the same reference numerals unless there is a special reason.

  FIG. 1 shows an example of a stabilized light source 100 that is part of the configuration example of the present invention and that is wavelength stabilized by locking the oscillation wavelength of the laser light source 101 to the resonance wavelength of the optical resonator 105. This is in line with the PDH method. In this example, a semiconductor laser is used as the laser light source 101, and the oscillation wavelength can be slightly adjusted by changing the applied current. The output laser light is branched by the beam splitter 107. The isolator 102 prevents disturbance due to the return light of the oscillation operation of the laser light source 101. The light whose phase is modulated by the signal from the oscillator 110 in the optical modulator 103 is adjusted by the half-wave plate 111 and the polarization beam splitter 104 and enters the optical resonator 105. The output light from the optical resonator passes through the isolation quarter-wave plate 106, is reflected by the polarization beam splitter 104, and enters the photodetector 108. The feedback light is converted into an electric signal by the photodetector 108, and is synchronously detected by the signal from the oscillator 110 in the synchronous detector 209. The output of the synchronous detection is smoothed by the PID 112 and returned to the semiconductor laser. With this feedback loop, the output wavelength of the laser light source can be locked to the resonance spectrum of the optical resonator. The full width at half maximum of the output light of the laser light source 101 in the state where feedback control is not performed as described above is larger than the full width at half maximum of the resonance (resonance) spectrum of the optical resonator 105. However, in general, the full width at half maximum of the output light of the laser light source 101 locked by the feedback control is smaller than the full width at half maximum of the resonance (resonance) spectrum of the optical resonator 105.

  As a matter of course, the above-described locking operation enables the wavelength adjustment speed of the laser light by the feedback signal of the stabilized light source 100 as the probe light generation means to be suppressed. The resonance wavelength of the Fabry-Perot optical resonator to be suppressed Must be greater than the drift velocity of In other words, the frequency band of the drift that can be suppressed is limited to the frequency band of feedback control by the feedback signal.

  Here, as the optical resonator, the temperature is controlled in the millikelvin range using the ULE spacer as described above, and the optical resonator is stabilized by using in a state where the external vibration is cut off, or a predetermined atom or ion. The absorption spectrum may be used.

  FIG. 2 shows an example of a part different from the above, which is a part of the configuration example of the present invention. FIG. 2 is a block diagram of a stabilized light source 200 that has been wavelength-stabilized by locking to the resonant wavelength of the optical resonator 205 when laser light 201 is input instead of the laser light source 101 of the stabilized light source 100. . In this example, the wavelength is made variable by shifting the laser beam 201 by the wavelength shifter 202. Further, the feedback signal that is the output of the synchronous detector 209 is smoothed by the PID 112, and then converted into a wavelength shifter signal including an AC signal having a frequency corresponding to the strength of the feedback signal by the VCO (voltage controlled oscillator) 213. The The frequency offset of the wavelength shifter signal can be set by adjusting the voltage of the offset voltage source 214. The stabilized light source 200 outputs an electrical signal reflecting the wavelength variation of the incident laser beam 201 with the optical resonator 205 as a reference (output b). Here, the modulation for the PDH method is performed using the independent optical modulator 203, or the modulated output light from the stabilized light source 201 can be used. As a matter of course, a synthesizer type signal generator can be used instead of the VCO.

  Also in this case, as in the case of the stabilized light source 100 described above, the speed at which the wavelength of the laser beam can be adjusted by the feedback signal of the stabilized light source 200 serving as the probe light generating means is reduced. It needs to be larger than the drift speed of the resonance wavelength of the resonator. In other words, the frequency band of the drift that can be suppressed is limited to the frequency band of feedback control by the feedback signal.

FIG. 3 shows an example of a composite optical resonator 300 used in an acceleration sensor using a plurality of optical resonators provided in a common spacer of the present invention, and FIG. 4 shows an example of an acceleration sensor using the composite optical resonator 300. As shown in FIG. FIG. 3 shows the result of numerical simulation when an acceleration of 9.8 m / s ² corresponding to the gravitational acceleration on the ground is applied to the optical resonator in the direction of the arrow in the figure, together with the configuration example of the optical resonator. The displacement distribution in the optical axis direction (z direction) at each point due to the strain occurring in the optical resonator is shown. The dark-colored portion has a large distortion, which is depressed on the resonator B side and travels on the C side.

  A composite optical resonator 300 shown in FIG. 3 has, for example, the above ULE barrel spacers as vertical common spacers, four vertically parallel cavities, and high-reflectivity reflecting mirrors at both ends of the cavities. The composite optical resonator includes M1, M2, A1, A2, B1, B2, C1, and C2, and uses each cavity as an optical resonator (310, 310A, 310B, 310C). Incidentally, M1 and M2 are those of the optical resonator at the center, and the others are those of the surrounding optical resonator. One of the cavities (the optical cavity 310 of the central cavity) includes the center line of the barrel-shaped spacer so that the center line coincides with the center line of the cavity. In this example, the other cavities (optical resonators 310A, 310B, and 310C) are arranged at the positions to be rotated around the central cavity and equidistant from the center. In the example of the arrangement of the cavities, one of the cavities is provided at a position including the center line, and the other cavities are provided at positions not including the center line and at symmetrical positions with respect to the center line. As a constituent material of the common spacer, a single crystal such as silicon or sapphire can be used in addition to the low thermal expansion glass such as ULE. In this case, secular change can be suppressed, but higher temperature control may be required.

  The common spacer has a support base or frame on the outer periphery thereof and supports it by providing a support portion. For this support, a support tool extending upward from the pedestal, a support tool hanging from above, or the like can be used. For example, when each cavity is provided at an equal distance at a position on the circumference of the center line of the common spacer, the circumference is equally divided and provided between two support points of the support portion.

FIG. 4 shows an example of an acceleration sensor 400 using a plurality of optical resonators provided in a common spacer of the present invention. This uses a composite optical resonator 300 shown in FIG. First, the laser light from the laser light source 501 is locked to the optical resonator 410 in the same configuration as that of the stabilized light source 100 in FIG. 1, and the laser light is branched by the optical branching device 407 and branched to the branching devices 407A, 407B, and 407C. Sent sequentially. The laser beam branched by the optical splitter 407 corresponds to the output a from the stabilized light source 100. In this configuration, the laser beams stabilized by the optical resonator 410 are branched and supplied to the optical resonators 410A, 410B, and 410C disposed around the optical resonator 410. For example, the configuration of the tuning unit 250 of FIG. 2 can be applied to the tuning units 402A, 402B, and 402C. Also, the output b branched from the VCO in FIG. 2 corresponds to the frequencies f _A , f _B , and f _C for each of the resonators described above. As is well known, the frequency and the phase are the same, and when detecting a minute frequency change, it is often performed to detect a phase change for a phase obtained by multiplying the angular velocity by time. Since the frequencies f _A , f _B , and f _C include offsets that are not caused by the applied acceleration, it is desirable to reduce the frequencies.

The signal having the frequency f _A is converted into a voltage signal (or current signal) proportional to the acceleration (a _x ) in the x direction by using a converter 403 that converts the frequency into current or voltage. Further, the signals of the frequencies f _B and f _C are mixed by taking a signal product in the frequency mixer 404, and the low frequency side filter 405 selects the low frequency side band component. The sideband component is converted into a voltage signal (or current signal) proportional to the acceleration (a _y ) in the y direction by using the converter 406. By subtracting the offset in the output of this conversion, it is possible to substitute for subtracting the frequency as described above. Further, the converters 403 and 406 may convert the signals into digital signals and output them. At this time, it is desirable to digitally convert the amount obtained by removing the offset.

Also, the frequency f _A, f _B, for f _C, to convert into a digital signal by using a frequency counter or phase meter each, the frequency f _A is a linear function of the x-direction acceleration (a _x) Since the difference between the frequencies f _B and f _C is a linear function of the acceleration (a _y ) in the y direction, the above multiplier and filter can be easily replaced with a digital arithmetic unit.

In the example of the acceleration sensor 500 using a plurality of optical resonators provided in the common spacer shown in FIG. 5, the signals of the frequencies f _B and f _C in FIG. 4 are mixed by taking a signal product in the frequency mixer 504. The low-frequency side filter 506 selects the low-frequency sideband signal component. The sideband signal is converted into a current signal (or voltage signal) proportional to the acceleration (a _y ) in the y direction by using the converter 508. Further, the high frequency side filter 509 selects a high side band component of the signal resulting from the above mixing of the signals of the frequencies f _B and f _C , and passes this signal through the frequency divider 510 to a half frequency. The frequency-divided signal, the signal of frequency f _A and the signal product are mixed by the frequency mixer 503, and the low-frequency side filter 505 selects the low-frequency sideband signal component. This selected signal is converted into a current signal (or voltage signal) proportional to the acceleration (a _x ) in the x direction using the converter 507. The converters 507 and 508 may output digital signals.

Similarly to the case of the first embodiment, each of the frequencies f _A , f _B , and f _C is converted into a digital signal using a frequency counter or a phase measuring device, so that the frequencies f _B and f _C the difference between the average and the frequency f _a of becomes a linear function of the x-direction acceleration (a _x), also, the difference between the frequency f _B and f _C is the linear function of y direction of the acceleration (a _y), The above multiplier and filter can be easily replaced with a digital arithmetic unit.

  The acceleration applied to the composite optical resonator can be actively suppressed using the output of the acceleration sensor. This suppresses the acceleration applied to the composite optical resonator 300, and particularly suppresses the acceleration applied to the optical resonators 310 and 410, thereby further stabilizing the frequency of the optical output in FIG. 4 or FIG. be able to.

  6 and 7 show configuration examples for suppressing the acceleration applied to the composite optical resonator 300 by using the acceleration output for negative feedback.

6A is a front view and FIG. 6B is a plan view of the composite optical resonator on the second vibration isolation table 602 supported by the vibration isolation column columns 603x, 603y, and 604 on the first vibration isolation table 601. Is supported by the composite optical resonator columns 605A, 605B, and 605C. For example, drive elements 610x and 610y and springs 606x and 606y made of electrostrictive elements or magnetostrictive elements are provided between the composite optical resonator column and the second vibration isolation table 602, and drive voltages Vx and Vy are applied and detected. Contrary to the acceleration vector, the active vibration isolator is configured to suppress vibration acceleration applied to the composite optical resonator by driving in the x and y directions. The composite optical resonator 300 is installed on the second vibration isolation table 602. After the acceleration output is amplified, it is applied to the driving elements 610x and 610y with a polarity that suppresses the acceleration. The drive voltages Vx and Vy can be obtained by processing according to the block diagrams of FIGS. 4 (403 to 406) and FIG. 5 (503 to 510) as described in the first embodiment, but are digitized. As for the f _A , f _B , and f _C , as shown in FIG. 6C, the arithmetic unit 605 converts the drive voltage Vx, Vy can be obtained. The drive element may be arranged so as to face each other with the second vibration isolation table 602 sandwiched so that the action of the electrostrictive element or magnetostrictive element is push-pull. However, in this case, in order to prevent a new strain from being induced in the optical resonator by the pair of drive elements serving as the push-pull, it may be effective to sandwich the spring between the drive element and the second vibration isolation table 602. is there.

  7A is a front view and a plan view of FIG. 7B is a diagram in which the composite optical resonator 300 on the first vibration isolation table is driven in three directions by an electrostrictive element or a magnetostrictive element. In addition to supporting the optical resonator 300, the electrostrictive element and the magnetostrictive element drive the movement on the xy plane. The acceleration output is converted from the xy orthogonal binary vector into each component of a ternary vector intersecting at an angle of 120 degrees, and after being amplified, applied to the electrostrictive element or magnetostrictive element with a polarity that suppresses the acceleration. To do.

In the case of FIG. 7C, the negative feedback is realized by converting each of the frequencies f _A , f _B , and f _C converted into digital signals into digital signals using a frequency counter or a phase measuring device. Therefore, it is easy to construct a conversion matrix for inputting these values and converting them into current values and voltage values to be applied to the respective electrostrictive elements and magnetostrictive elements.

  In general, in the case of driving with the above-described ternary vector, a new distortion is easily generated in the optical resonator by combining the force with the spacer of the optical resonator. It is easy to make a structure in which no distortion occurs in the optical resonator by using a frame or a stand different from the above.

  According to the present invention, the problem that it has conventionally been difficult to eliminate the influence of ground vibration of 1 Hz or less in a space-saving manner in an optical resonator is saved. At present, an optical resonator of 10 minus 16s with a stability of 1 second has been realized, and further improvement of vibration isolation performance is required for further improvement. Conventionally, it has been difficult to distinguish the aging effect of resonator materials in the low range from the change in resonator length due to vibration, but the aging effect is reduced by using a single crystal material as a resonator. Therefore, the present invention solves this point. Further, even in a portable or satellite-mounted local optical frequency oscillator in which it is difficult to use a heavy vibration isolation table, vibration isolation performance can be provided by using the present invention. In addition, in the ultimate optical resonator operated at extremely low temperatures, a prescription for the vibration of the refrigerator is required. The present invention is also effective as vibration isolation for the refrigerator vibration.

DESCRIPTION OF SYMBOLS 100 Stabilized light source 101 Laser light source 102 Isolator 103 Optical modulator 104 Polarizing beam splitter 105 Optical resonator 106 Quarter wave plate 107 Branch device 108 Photo detector 109 Synchronous detector 110 Oscillator 111 Half wave plate 112 PID
200 Stabilizing light source 201 Laser light 202 Wavelength shifter 203 Optical modulator 204 Polarization splitter 205 Optical resonator 206 Quarter wave plate 208 Photo detector 209 Synchronous detector 210 Oscillator 211 Half wave plate 212 PID
213 VCO
214 Offset voltage source 250 Tuning unit 300 Compound optical resonator 310, 310A, 310B, 310C Optical resonator 400 Acceleration sensor 402A, 402B, 402C Tuning unit 403 Frequency voltage converter 404 Frequency mixer 405 Low frequency side filter 406 Frequency voltage Converter 407, 407A, 407B, 407C Optical splitter 410, 410A, 410B, 410C Optical resonator 500 Accelerometer 503, 504 Frequency mixer 505, 506 Low frequency side filter 507, 508 Frequency voltage converter 509 High frequency side filter 510 Divider 601, 602 Anti-vibration table 603x, 603y, 604 Anti-vibration table column 605A, 605B, 605C Compound optical resonator column 606x, 606y Spring 610x, 610y Drive element 701 Anti-vibration table 710A, 710B 710C drive element

Claims (6)

An acceleration sensor that detects the acceleration by measuring a change in the resonance frequency of a Fabry-Perot optical resonator using a laser beam,
A composite optical resonator comprising a plurality of optical resonators;
Acceleration deriving means for deriving acceleration applied to the composite optical resonator from at least two comparisons of the resonance frequencies of the plurality of optical resonators,
The composite resonator is a composite optical resonator including cavities for three or more optical resonators using a spacer having a rotational symmetry with respect to a center line as a common spacer,
Each of the cavities is parallel to each other,
One of the cavities is provided at a position including the center line, and the other cavity is provided at a symmetric position with respect to the center line at a position not including the center line. The composite optical resonator is provided with an optical path in the direction of gravity,
Supported at a support point in the support provided on the outer periphery of the common spacer,
Each of the support points is provided at a position equidistant from the center line on an equidistant surface from any two of the cavities provided at a position not including the center line. The acceleration sensor according to claim 1. The number of the optical resonators and the number of support points provided at positions not including the center line are 3, respectively.
The optical resonators are sequentially designated as A, B, and C, and the support points on the opposite sides of the center lines of A, B, and C are the support points A, B, and C, and the support points A, B, and C are When the orthogonal coordinate on the plane including the xy coordinate, the x-axis direction is the direction from the center line toward the support point A, and the y-axis direction is the direction from the support point C to the support point B,
The acceleration deriving means derives an acceleration in the y direction from a difference between respective resonance frequency shifts from the optical resonator provided at a position including the center lines of B and C, and an x direction acceleration as the center of the A. 3. The acceleration sensor according to claim 1, wherein the acceleration sensor is derived from a resonance frequency shift from the optical resonator provided at a position including a line. The number of the optical resonators provided at positions not including the center line and the number of the support points are each 3,
The optical resonators are sequentially designated as A, B, and C, and the support points on the opposite sides of the center lines of A, B, and C are the support points A, B, and C, and the support points A, B, and C are When the orthogonal coordinate on the plane including the xy coordinate, the x-axis direction is the direction from the center line toward the support point A, and the y-axis direction is the direction from the support point C to the support point B,
The acceleration deriving means derives the y-direction acceleration from the difference between the respective resonance frequency shifts from the optical resonator provided at the position including the center line of B and C, and determines the acceleration in the x-direction as B and Subtracting the resonance frequency shift from the optical resonator provided at the position including the center line of A from the average of the resonance frequency shift from the optical resonator provided at the position including the center line of C The acceleration sensor according to claim 1, wherein the acceleration sensor is obtained.   Resonance frequency shifts of A, B, and C are incident on the optical resonators A, B, and C, respectively, and the laser beams locked to the optical resonators provided at positions including the center line. The acceleration sensor according to claim 3, wherein the acceleration sensor is a deviation of each of the resonance frequencies of A, B, and C from the frequency. A driven table on which the composite optical resonator is mounted;
A drive system for driving the driven table so as to move on the surface;
A negative feedback circuit that applies negative feedback by applying the output of the acceleration deriving means to the drive system,
6. An active vibration isolator using an acceleration sensor according to claim 1, wherein the negative feedback suppresses the output of the acceleration detecting means.

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