A device for quickly measuring the direction of Raman light

Abstract

The present invention discloses a device for rapid measurement of Raman light direction, which is applied to an atomic interferometer gravimeter, and includes an aperture, a beam splitter, a retroreflector, a liquid container, a plano-convex lens, and a spot position detector, wherein the aperture is used to limit the diameter of the Raman light emitted by the atomic interferometer gravimeter to obtain a thinner Raman light beam; the beam splitter is used to split the Raman light beam into two beams, one of which is reflected by the upper surface of the beam splitter and incident on the retroreflector, and then reflected back along the original direction, and irradiated on the spot position detector through the plano-convex lens after being transmitted by the beam splitter; the other beam continues to pass through the vacuum cavity of the atomic interferometer gravimeter after transmitting the beam splitter, irradiates on the horizontal liquid surface, passes through the vacuum cavity again after being reflected by the liquid surface and irradiates on the lower surface of the beam splitter, and irradiates on the spot position detector through the plano-convex lens after being reflected. The present invention can realize rapid measurement of the Raman light direction, and can effectively improve the measurement accuracy of the Raman light direction.

Description

Technical Field

[0001] The invention belongs to the technical field of atomic interferometer gravimeters, and more specifically, relates to a device for quickly measuring the direction of Raman light. Background Art

[0002] The gravitational acceleration on the Earth's surface originates from the Earth's gravitational force and centrifugal force on objects. It is an important parameter of the Earth's gravitational field, and its accurate measurement is of great significance in many fields such as basic physics, geophysics, gravity navigation, and resource exploration. The atomic interferometer gravimeter uses cold atoms falling freely in a vacuum environment as test mass, and realizes absolute gravity measurement based on the atomic interference process. Compared with the traditional falling cone absolute gravimeter, it has higher potential sensitivity.

[0003] Generally speaking, the atomic interference process can be achieved by coherently manipulating atoms with lasers, and this laser beam is Raman light. In the atomic interference gravity measurement process, the measurement result is the projection of gravity acceleration in the direction of Raman light. When there is an angle θ between the Raman light direction and the gravity acceleration direction, the gravity measurement result will be biased, such as Figure 1 As shown, the effect of the angle θ on the gravity measurement is to introduce a measurement result deviation Δg = g*θ 2 / 2. Raman light direction deviation is an important systematic error term in atomic interferometry gravity measurement. When the angle θ reaches 1mrad, the gravity measurement deviation introduced by it will be as high as 500μGal (1μGal = 10 -8 m / s 2 ). In order to effectively correct the gravity measurement deviation, it is necessary to optimize the direction of the Raman light, measure the angle θ between it and the direction of gravity acceleration, and obtain the actual angle between it and the direction of gravity acceleration.

[0004] At present, the Raman light direction measurement and evaluation methods used in atomic interferometer gravimeters mainly include:

[0005] a) The paper Chin.Phys.B 29 073701 discloses a method for measuring the direction of Raman light based on a modulation experiment used in an atomic interferometer gravimeter. The method modulates the direction of the Raman light collimating beam expander, uses an inclinometer to record the change in the direction of the beam expander, and records the change in the atomic interferometer gravity measurement value. By fitting the change relationship between the inclinometer reading and the gravity measurement value, the inclinometer reading when the Raman light is consistent with the gravity acceleration direction is obtained, and the direction of the beam expander is adjusted so that the inclinometer reading is at this value.

[0006] b) In the invention patent 202021973432.8, a method for measuring the direction of Raman light based on a modulation experiment applied to an atomic interferometer gravimeter is disclosed. This method modulates the overall attitude of the atomic gravimeter, uses an inclinometer to record changes in the instrument attitude, and records changes in the atomic interferometer gravity measurement value. By fitting the change relationship between the inclinometer reading and the gravity measurement value, the inclinometer reading when the Raman light is in the same direction as the gravity acceleration is obtained, and the overall attitude of the instrument makes the inclinometer reading at this value.

[0007] Both methods of measuring the direction of Raman light require modulation of the direction of Raman light, and the modulation experiment is time-consuming. Moreover, both methods require the measurement results of the gravimeter as a criterion. While the measurement results change during the modulation process of the Raman light direction, they will also be affected by environmental factors such as groundwater and atmospheric pressure and cause deviations. This will directly affect the acquisition of the position of the maximum point of the gravity measurement value during the Raman light modulation process, and thus affect the accuracy of the Raman light direction measurement results. Summary of the invention

[0008] In view of the defects of the prior art, the purpose of the present invention is to provide a device for quickly measuring the direction of Raman light, which saves the time consumption of traditional modulation experiments, can quickly measure the direction of Raman light, is less affected by environmental factors, and can effectively improve the measurement accuracy.

[0009] To achieve the above object, the present invention provides a Raman light direction rapid measurement device, which is applied to an atomic interferometer gravimeter, and includes an aperture, a beam splitter, a retroreflector, a liquid container, a plano-convex lens, and a light spot position detector, wherein the light spot position detector is arranged at the object focal plane of the plano-convex lens;

[0010] Among them, the aperture is used to limit the diameter of the Raman light emitted by the collimating beam expander in the atomic interferometer gravimeter to obtain a Raman light beam with the same direction as the Raman light and a diameter of 1.8mm to 2.2mm; the beam splitter is used to split the Raman light beam into a reference light beam and a light beam to be measured, the reference light beam is reflected by the upper surface of the beam splitter and then incident on the retroreflector, then reflected back by the retroreflector along the incident direction, and irradiated on the light spot position detector through the plano-convex lens after being transmitted through the beam splitter; the light beam to be measured is transmitted through the beam splitter, passes through the vacuum cavity in the atomic interferometer gravimeter, and is incident on the liquid surface in the liquid container, then passes through the vacuum cavity again after being reflected by the liquid surface and irradiates on the lower surface of the beam splitter, and then irradiates on the light spot position detector through the plano-convex lens after being reflected by the beam splitter.

[0011] The Raman light direction rapid measurement device provided by the present invention is built in an atomic interferometer gravimeter, uses the horizontal liquid surface as a criterion for measuring the angle between the Raman light and the direction of gravity acceleration, then uses a plano-convex lens to converge the measured light beam and the reference light beam, and then uses a light spot position detector to measure the spacing of the light spots formed by the two light beams at the object focal plane, and converts the angle measurement into position measurement, thereby realizing the measurement of the Raman light direction, saving the time consumption of traditional modulation experiments, and can quickly realize the measurement of the Raman light direction; at the same time, using the horizontal liquid surface as a criterion, it is less affected by environmental factors and can effectively improve the measurement accuracy.

[0012] In one of the embodiments, the beam splitter is disposed below the aperture and is located on the optical axis of the aperture at an angle of 45° to the aperture.

[0013] In one of the embodiments, the aperture is a small hole aperture with a diameter of 2 mm.

[0014] In one embodiment, the beam splitter is a parallel plate, a polarization beam splitter or a film beam splitter.

[0015] In one embodiment, the liquid in the liquid container is alcohol.

[0016] In one of the embodiments, the liquid in the liquid container is mercury.

[0017] In one of the embodiments, the light spot position detector is a four-quadrant detector or a lateral position sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of a traditional atomic interferometer gravimeter probe;

[0019] Figure 2 It is a schematic diagram of the structure of a device for rapid measurement of Raman light direction provided by an embodiment of the present invention;

[0020] Figure 3 It is a schematic diagram of two beams of light incident on a plano-convex lens provided by the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0022] In order to solve the problem that the traditional Raman light direction measurement method needs to modulate the direction of Raman light, which leads to a long measurement time and is greatly affected by environmental factors, resulting in low measurement accuracy, the present invention provides a Raman light direction rapid measurement device, which can save the time consumption of modulation experiment, quickly realize the measurement of Raman light direction, and is less affected by environmental factors, thereby effectively improving the measurement accuracy.

[0023] Figure 2 It is a structural schematic diagram of a Raman light direction rapid measurement device provided by an embodiment of the present invention. The Raman light direction rapid measurement device is mainly used in an atomic interferometer gravimeter, that is, the device is additionally built in the atomic interferometer gravimeter, and the liquid surface is used as a horizontal plane criterion. The angle between the Raman light beam incident on the liquid surface and the direction of gravitational acceleration is θ, and the angle between the Raman light beam and the incident direction after being reflected by the liquid surface is 2θ. The angle θ between the Raman light and the direction of gravitational acceleration is obtained by measuring the deflection angle of the light beam direction before and after the incident.

[0024] like Figure 2 As shown, the entire Raman light direction rapid measurement device provided in this embodiment mainly includes an aperture 10, a beam splitter 20, a retroreflector 30, a liquid container 40, a plano-convex lens 50 and a light spot position detector 60, and the light spot position detector 60 is arranged at the object focal plane of the plano-convex lens 50.

[0025] The aperture 10 provided in this embodiment is used to limit the diameter of the Raman light emitted by the collimating beam expander 70 in the atomic interferometer gravimeter, so as to obtain a Raman light beam with the same direction as the Raman light and a diameter of 1.8 mm to 2.2 mm.

[0026] It should be noted that, in general, the diameter of the Raman light emitted by the collimating beam expander 70 is 20 mm, which is not conducive to its control during the measurement process. In this regard, the present embodiment may add an aperture 10 below the collimating beam expander 70 and on its optical axis to limit the diameter of the Raman light emitted by the collimating beam expander 70 to obtain a thinner Raman beam A. Specifically, the aperture 10 provided in the present embodiment may adopt a small aperture aperture with a diameter of 1.8 mm to 2.2 mm to obtain a Raman beam A with a diameter of 1.8 mm to 2.2 mm. Preferably, the aperture 10 may adopt a small aperture aperture with a diameter of 2 mm to obtain a Raman beam A with a diameter of 2 mm, so as to facilitate the control of the beam during the measurement process.

[0027] The beam splitter 20 provided in this embodiment is used to split the Raman beam A into two. Figure 3 As shown, the Raman beam is divided into a reference beam A1 (reflected beam) and a measured beam A2 (transmitted beam). Specifically, the beam splitter 20 provided in this embodiment can be a parallel plate, a polarization beam splitter or a thin film beam splitter.

[0028] The reference beam A1 is incident on the retroreflector 30 and returns along the original direction. That is, the reference beam A1 is reflected by the upper surface of the beam splitter 20 and then incident on the retroreflector 30, and then reflected back along the incident direction by the retroreflector 30, and after being transmitted through the beam splitter 20, it is irradiated on the spot position detector 60 through the plano-convex lens 50. Figure 3 Where A1* represents the reference beam after being transmitted through the beam splitter 20.

[0029] The light beam A2 to be measured passes through the beam splitter 20, passes through the vacuum cavity 80 in the atomic interferometer gravimeter, and is incident on the liquid surface 42 in the container 40. Then, after being reflected by the liquid surface 42, it passes through the vacuum cavity 80 again and is irradiated on the lower surface of the beam splitter 20. Then, after being reflected by the beam splitter 20, it is irradiated on the light spot position detector 60 through the plano-convex lens 50. Figure 3 A2* represents the light beam to be measured after being reflected by the liquid surface, and A2″ represents A2* after being reflected by the lower surface of the beam splitter 20.

[0030] In this embodiment, for the liquid container 40, due to the fluidity of the liquid and the influence of gravity, the liquid level of the liquid container 40 will always remain in a horizontal state. When the light beam A2 to be measured passes through the beam splitter 20 and then passes through the vacuum cavity 80 in the atomic interferometer gravimeter and is incident on the liquid container 40, it can be effectively ensured that the light beam A2 to be measured always maintains an angular deviation of 2θ from the incident direction after being reflected by the liquid surface 42, wherein θ is the angle between the direction of the Raman light and the direction of gravitational acceleration.

[0031] Figure 3 It is a schematic diagram of two beams incident on the plano-convex lens 50. In the figure, the dotted line perpendicular to the beam splitter 20 and the dotted line perpendicular to the liquid surface both represent normal lines. The Raman beam A is split into two by the beam splitter, one of which is the reference beam A1 (reflected beam). According to the incident angle equal to the reflection angle in the light reflection, a=c, and because of the diagonal relationship, a=b, so b=c. The other is the measured beam A2 (transmitted beam). The measured beam A2 is reflected by the lower surface of the beam splitter 20. According to the incident angle equal to the reflection angle in the light reflection, f=e, and because of the diagonal relationship, e=g, so f=g. According to the triangle exterior angle theorem, the angle between the two light beams (A1* and A2”) incident on the plano-convex lens is 2θ, and the spot spacing formed by the two on the object focal plane of the plano-convex lens 50 is d=2θ*f, where f is the focal length of the plano-convex lens 50. Therefore, by measuring the spot spacing d with the spot position detector 60 located at the object focal plane of the plano-convex lens 50, the angle θ between the Raman light and the direction of gravity acceleration can be measured, that is, θ=d / 2f.

[0032] At the same time, according to the above analysis, no matter how many degrees the Raman light beam passes through the beam splitter, the device can measure the direction of the Raman light. In this regard, the beam splitter 20 provided in this embodiment only needs to be installed on the optical axis of the aperture, and the installation angle between it and the aperture 10 can be set arbitrarily, and this embodiment does not limit it. Preferably, the beam splitter 20 provided in this embodiment can be set to 45 degrees with the aperture 10, which can ensure that the two beams incident on the plano-convex lens are within a reasonable range, which is convenient for the spot position detector to perform position measurement.

[0033] The device for rapid measurement of the direction of Raman light provided in the present embodiment is built in an atomic interferometer gravimeter, and uses the horizontal liquid surface as a criterion for measuring the angle between the Raman light and the direction of gravity acceleration, and then uses a plano-convex lens 50 to converge the measured light beam and the reference light beam, and then uses a spot position detector 60 to measure the spacing of the spots formed by the two light beams at the object focal plane, and converts the angle measurement into a position measurement, thereby realizing the measurement of the direction of Raman light, saving the time consumption of traditional modulation experiments, and can quickly realize the measurement of the direction of Raman light; at the same time, using the horizontal liquid surface as a criterion is less affected by environmental factors, and can effectively improve the measurement accuracy.

[0034] In one embodiment, the liquid in the liquid container 40 provided in the above embodiment can be alcohol or mercury. Among them, alcohol has a smaller surface tension, and the liquid surface formed is closer to the ideal horizontal plane; mercury has a higher reflectivity on the surface, which is more conducive to improving the signal size measured by the device.

[0035] In one embodiment, the light spot position detector 60 provided in the above embodiment is mainly used to measure the spacing information of the light spots, and may be a four-quadrant detector or a lateral position sensor, and the position measurement accuracy may be higher.

[0036] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A device for rapid measurement of Raman light direction, used in atomic interferometer gravimeter, characterized in that: It includes an aperture, a beam splitter, a retroreflector, a liquid container, a plano-convex lens and a light spot position detector, wherein the light spot position detector is arranged at the object focal plane of the plano-convex lens; Among them, the aperture is used to limit the diameter of the Raman light emitted by the collimating beam expander in the atomic interferometer gravimeter to obtain a Raman light beam with the same direction as the Raman light and a diameter of 1.8mm to 2.2mm; the beam splitter is used to split the Raman light beam into a reference light beam and a light beam to be measured, the reference light beam is reflected by the upper surface of the beam splitter and then incident on the retroreflector, then reflected back by the retroreflector along the incident direction, and irradiated on the light spot position detector through the plano-convex lens after being transmitted through the beam splitter; the light beam to be measured is transmitted through the beam splitter, passes through the vacuum cavity in the atomic interferometer gravimeter, and is incident on the liquid surface in the liquid container, then passes through the vacuum cavity again after being reflected by the liquid surface and irradiates on the lower surface of the beam splitter, and then irradiates on the light spot position detector through the plano-convex lens after being reflected by the beam splitter.

2. The device for rapid measurement of Raman light direction according to claim 1, characterized in that: The beam splitter is arranged below the aperture and is located on the optical axis of the aperture at an angle of 45° to the aperture.

3. The device for rapid measurement of Raman light direction according to claim 1 or 2, characterized in that: The aperture is a small aperture with a diameter of 2 mm.

4. The device for rapid measurement of Raman light direction according to claim 1 or 2, characterized in that: The beam splitter is a parallel plate, a polarization beam splitter or a film beam splitter.

5. The device for rapid measurement of Raman light direction according to claim 1, characterized in that: The liquid in the liquid container is alcohol.

6. The device for rapid measurement of Raman light direction according to claim 1, characterized in that: The liquid in the liquid container is mercury.

7. The device for rapid measurement of Raman light direction according to claim 1, characterized in that: The light spot position detector is a four-quadrant detector or a lateral position sensor.

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