JPS63117278A - Photomagnetic resonance magnetometer - Google Patents

Abstract

PURPOSE:To enable the maintaining of a high sensitivity, by mounting an aperture made up of a non-magnetic body having openings required for parallel light portions of a light beam. CONSTITUTION:In this magnetometer, apertures 12 are mounted between absorption cells 4 and lenses 2. Spectral lights from a light source lamp 1 are introduced to the apertures 12 through optical fibers 11, the lenses 2, circular polarization plates 3 and the absorption cells 4. Here, the apertures 12 are allowed to make a photomagnetic resonance curve axially symmetrical almost perfectly in clockwise and counter-clockwise circular polarization systems. Output lights from the apertures 12 are converted into electrical signals with a photo detector 5 through the lenses 2 and the optical fibers 11 and added up with an adder 7 through six amplifiers 6. A signal processor 8 sends out specified signals to three pairs of RF coils 9 set near three pairs of cells 4 by a signal from the adder 7. This system is made to lock-on at the optimum point of a photomagnetic resonance and a lock-on frequency is sent outside as output signal.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention detects the presence of submarines in the sea using bin points (P
The present invention relates to an optical magnetic resonance magnetometer that detects in Po1nt.

[Conventional technology]

Figure 4 shows a typical example of a conventional optical magnetic resonance magnetometer. (1) is a light source lamp, (2) is a lens, (3) is a circularly polarizing plate, (4) is an absorption cell, (51 is a photodetector, (6
1 is an amplifier, (71 is an adder, (8) is a signal processor, (
9) is an RF coil, 1G is the central axis in the optical axis direction, and αD is an optical fiber. In the figure, components not related to the present invention are omitted. Light source lamp (11 is approximately φ8mX1 (
A 1m cylindrical container is used to supply gaseous helium as the main gas, and a small amount of krypton gas as the ignition gas. The optical fiber I is a Si (silicon) optical fiber with a core diameter of about 50 μm and has a length of about 85 cra, and guides the 6 μm spectrum light from the light source lamp +11 to the focal plane of the lens (2). The spectral light from the original fiber (Iυ) is converted into parallel light.The circularly polarizing plate (3) has opposite polarity to the pair of absorption cells (4) in 2 (1), and one is a right-handed polarizing plate (σ + ) and the other is a left-handed circularly polarizing plate (σ-9).The absorption cell (4) is approximately φ
It is a cylindrical container measuring 40a+40m, with gaseous helium as the main gas and a trace amount of xenon gas as the ignition gas. The lens (2) collects the light beam that has passed through the absorption cell (4). ft, the fiber αυ is installed at its aperture surface or the focal plane of the lens (2), and is a Si (silicon) based optical fiber with a core diameter of about 50 μm and a length of about 85 mm.

Photodetector (51 is 1.81 (81 is highly sensitive in the Of1 μm band)
Silicon-based APD (Avalanche P
The output light from the source fiber aυ is converted into an electrical signal by a diode].

The amplifier (6) amplifies the signal from the photodetector (51) while maintaining the required signal-to-noise ratio (S/N). The signal processor (81) uses the signal from the adder (7) to add the three pairs of RF coils (9) installed near the three pairs of absorption cells (4). A signal is sent to lock the system to the optimal point of optical magnetic resonance occurring in the absorption cell (4), and the lock-on frequency is sent to the outside as an output signal. The lock-on frequency is the absorption cell (
4) Since it is proportional to the strength of the magnetic field at the base, by measuring the lock-on frequency, it is possible to know, for example, the strength of the earth's magnetism. In the field of gaseous helium, there is a relationship of 28 calm e.

Figure 3 (1)), fc) is a pair of absorption cells (4)l
This shows the central axis αG in the corresponding original axis direction, which is the A axis in this case.

They will be referred to as the B axis and the C axis. The angle formed by each axis with respect to the horizontal plane is 45 degrees as shown in Figure 3 (B).

The angle formed by each axis with respect to the horizontal direction is 120 degrees, as shown in FIG. 3(Q).

The above-mentioned optical magnetic resonance magnetometer is AFC (Aut.

This is called the Frequency C0ntralJ method, and its one-axis sensitivity finger synchrony S is expressed by the following equation.

9 = KC8b2θ filK: Constant θ: Optical axis (The angle between the center @- and the magnetic field in Figure 5 is (1
1 shows a pattern in a vertical plane. A
By arranging the axes, B-axes, and C-axes three-dimensionally as described above, the sensitivity directivity pattern of equation (1) is overlapped (overRapJ), and the inclination angle of the geomagnetic field is 190 degrees to +90 degrees, In other words, it operates in all nine worlds.

[Problem to be solved by the invention] Conventional ″/l,
The magnetic co-Sa force meter has a high static sensitivity of Q,01nT or more, but when this magnetometer is mounted on an anti-submarine patrol aircraft and used for submarine detection operations, it becomes difficult to maneuver aircraft, etc. (Maneuver), a spurious signal larger than 0.01 nT was generated, and the above-mentioned high sensitivity of 0.01 nT or more could not be utilized during operation.

It is known that the optical magnetic resonance point of gaseous helium, which has a Zeeman sublevel, shifts minutely due to changes in the angle between the optical axis and the external magnetic field.

Therefore, as explained in Figure 3, a flea and two absorption cells (
4) with a circularly polarizing plate (3) of opposite polarity, as shown in Figure 5, the optical magnetic resonance curve (resonance point A) of the system using right-handed circularly polarized light (σ0) is obtained. An adder (7) adds the optical magnetic resonance curve MA (resonance point B) of the system using circularly polarized light (σ-).
By operating the entire system at the resonance point C of the optical a-air resonance tuner that is added and synthesized in , the above-mentioned shift in the resonance point is reduced. However, the non-uniformity of the cross-sectional brightness distribution of the light 2
Sun polarizer (31 polarization summer imperfections, e, collection cell (4
；In the positive, the plasma ￥! ! Due to the non-uniformity of the summer and the surface feeling of the light holder (5), the fifth
It can be concluded that it is practically impossible to obtain an ideal resonance point as shown in the figure and to reduce spurious signals caused by maneuvers of an aircraft or the like to the level of static sensitivity.

This invention has been accomplished in order to solve the above-mentioned problems, and it is an object of the present invention to obtain an optical magnetic resonance magnetometer that can reduce the above-mentioned spurious signals to the level of static sensitivity using low-cost means. With the goal.

[Means for solving problems]

The optical magnetic resonance magnetometer according to the present invention is equipped with apertures made of a non-magnetic material and each having an aperture that is parallel to the 9-element beam.

[Effect]

In this invention, the aperture having the required opening can make the optical magnetic resonance curve in the right-handed circularly polarized light system and the optical magnetic resonance curve in the left-handed circularly polarized light system into completely axially symmetrical curves, and their synthesis The resonance point C of the opto-magnetic resonance curve is now not displaced by maneuvers of aircraft or the like.

〔Example〕

FIG. 1(a) is a block diagram of an embodiment of the present invention, and a3 is an aperture. Note that FIGS. 1(b) and (C) show the central axis 01 in the optical axis direction corresponding to the pair of absorption cells (4).
shows. Aperture α2 consists of absorption cell (4) and lens (2).
It is loaded between +. The A-axis will be explained below as an example. In this example, the opening diameter of the aperture (13) for the left-handed circularly polarized light system is φ30 mm, and (a
) The optical resonance curve (σ-) shown in fζ is obtained. Figure 2 (a) to (C) show that the clockwise circularly polarized system is
The opening diameter of the aperture α2 is approximately φ30m, φ3
1. The optical magnetic resonance curve (σ+) when the diameter is 29 mm is shown. At tc+ in Fig. 2, the above σ0 is an optical magnetic resonance curve that is symmetric about the x axis, and the composite optical magnetic resonance point C is an ideal point as explained in Fig. 5. The settings are as follows. Regarding the B axis and C axis,
By the same method as the A axis.

Each ideal resonance point can be obtained. As mentioned above.

The aperture aperture Ii is generally applied at the longest test adjustment stage.

〔·Effect of the invention〕

As described above, according to the present invention, the resonance points of synthetic optical magnetic resonance oil sand can be easily determined by maneuvers of aircraft, etc.
nθuber I made it so that it doesn't change depending on the moon, so 5
This makes it possible to maintain the high sensitivity of magnetic resonance magnetometers even during submarine detection operations, and the effect is considered to be extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the process of obtaining an ideal composite optical magnetic resonance point according to the present invention, and FIG. 3 is a diagram showing a conventional optical magnetic resonance magnetic field. Diagram showing meter,
FIG. 4 is a diagram showing a sensitivity finger co-injection pattern of an original AFC type magnetic resonance magnetometer, and FIG. 5 is a T diagram showing an optical magnetic resonance curve. In the figure, (1) is the light source lamp, (2) is the lens, (3) is the circularly polarizing plate, (4) is the absorption cell, (51 is the photodetector, and (6) is the light source lamp.
1 is an amplifier. (7) is an adder, (81 is a signal processor, (91 is an RF coil, αG is the center in the optical axis direction @, (lυ is the original fiber, α2
is the aperture. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] It has six absorption cells containing substances having Zeeman sublevels that cause quantum transition, and the central axes in the optical axis direction of the pair of absorption cells are set at 45 degrees and 120 degrees, respectively, with respect to the horizontal plane. an absorption cell part set at the same time, one light source lamp that generates the required spectrum, six optical fibers having the required length to guide the spectrum light of the light source lamp to the absorption cell, and a spectrum from the optical fiber. Six lenses that guide the light into parallel light to the absorption cells, and two absorption cells of the six absorption cells are paired, and two absorption cells corresponding to the pair of absorption cells and the absorption cells of the pair of absorption cells are formed. Two circularly polarizing plates with polarization characteristics of opposite polarities installed between the lenses, six apertures formed of a non-magnetic material having required openings in the parallel light portion of the six light beams, and the above-mentioned Six lenses that condense the light beams that have passed through the absorption cell; six optical fibers that have the required apertures on the focusing surfaces of the lenses and have the required lengths; and convert the light beams from the optical fibers into electrical signals. 6 photodetectors that convert into
six amplifiers for amplifying the signals from the photodetectors; an adder for adding the signals from the amplifiers; An optical magnetic resonance magnetometer comprising a pair of RF coils, a signal processor for processing the electrical signal from the adder, and means for feeding back the signal from the signal processor to the RF coil. .