Absolute gravimeter and method for measuring absolute gravity or gravity vertical gradient

Abstract

The application discloses an absolute gravimeter and a measuring method capable of measuring absolute gravity or gravity vertical gradient. The absolute gravimeter comprises a vacuum falling body system, an upper support adjusting system, a laser interference system, a vibration isolation system and a lower support adjusting system. The vacuum falling body system and the vibration isolation system are designed as cavities with interchangeability of the same connection interface, so that the positions of the two systems in the instrument erection process of different measurement modes are interchanged. The falling body prism in the vacuum falling body system and the reference prism in the vibration isolation system are both designed as a combination of bidirectional pyramidal prisms. In a high position measurement mode, the vacuum falling body system is above and the vibration isolation system is below, and the absolute gravity value at the high position is measured; in a low position measurement mode, the vibration isolation system is above and the vacuum falling body system is below, and the absolute gravity value at the low position is measured. The absolute gravity values at the high position and the low position are obtained through the two measurement modes respectively, and the effective height corresponding to the falling body is recorded, so that the measurement of the gravity vertical gradient is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to an improvement of absolute gravity measurement technology, belonging to the field of absolute gravimeter, and particularly relates to an absolute gravimeter and a measurement method capable of measuring absolute gravity or gravity vertical gradient. BACKGROUND

[0002] Gravity field is a basic geophysical field reflecting the structure and changes of the earth's interior. High-precision gravity observation data is the basis for the fields of earth science research, resource exploration, earthquake monitoring and prediction, and is also indispensable strategic data for submarine gravity aided navigation and missile guidance.

[0003] An absolute gravimeter is a precision instrument for directly measuring the value of gravity acceleration, and is one of the important means of gravity field observation. Due to the existence of gravity vertical gradient γ (the global average value is about -3.086 μGal / cm), even a small distance of the falling body will cause changes in the measurement results. In order to facilitate the application of subsequent gravity data, the gravity value is usually calculated from the equivalent height to the pier surface position through the gravity vertical gradient. At present, the measurement of gravity vertical gradient usually uses two high-precision relative gravimeters (the precision requirement is 20 μGal) to measure the difference between two points through multiple back-and-forth measurements between the two points at the pier surface and 1.3 m above the pier surface (the height reading precision requirement is 1 mm), and the gravity vertical gradient at the measurement point position is obtained by calculation. Therefore, when performing high-precision absolute gravity measurement, not only a high-precision absolute gravimeter needs to be carried, but also a high-precision relative gravimeter needs to be carried additionally, which greatly increases the procurement and transportation costs.

[0004] A high-precision absolute gravimeter measures the gravity value at the equivalent starting point position of the falling corner prism, which is about 1.3 m away from the ground for the currently commercial high-precision FG5 or FG5X type absolute gravimeter. The main parts of the body include a vacuum falling body system, an upper support adjustment system, a laser interference system, a vibration isolation system, a lower support adjustment system, etc. Generally, they are arranged in an up-down manner. The vacuum falling body system is at the uppermost end, supported by the upper support adjustment system, followed by the laser interference system, the vibration isolation system and the lower support adjustment system, and in addition, a control case and a data processing software system are needed. There is a corner prism in the vacuum falling body system and the vibration isolation system, which has the characteristic that the reflected light is parallel to the incident light. According to the current up-down arrangement, the corner prism in the vacuum falling body system can only reflect the incident light from bottom to top, and the corner prism in the vibration isolation system can only reflect the incident light from top to bottom. Directly replacing the positions of the vacuum falling body system and the vibration isolation system will not form a normal light path. SUMMARY

[0005] In view of the actual application requirements of the existing high-precision absolute gravity and gravity vertical gradient measurement and the deficiencies of the existing technology, the application provides an absolute gravity meter and a measurement method capable of measuring absolute gravity or gravity vertical gradient, a vacuum falling body system and a vibration isolation system connected through an interface are designed, the positions of the vacuum falling body system and the vibration isolation system are exchanged, absolute gravity values at high positions and low positions are obtained in two measurement modes respectively, and the effective heights of the falling bodies during erection in the two measurement modes are recorded, so that the gravity vertical gradient of the measurement point is calculated. Only one absolute gravity meter is required, and an additional high-precision relative gravity meter is not required, so that the measurement of high-precision absolute gravity and gravity vertical gradient can be realized, and the equipment for actual absolute gravity measurement is greatly simplified, and the procurement and transportation costs are saved.

[0006] To achieve the above object, the application provides an absolute gravity meter capable of measuring absolute gravity or gravity vertical gradient, comprising a vacuum falling body system, an upper support adjustment system, a laser interference system, a vibration isolation system and a lower support adjustment system.

[0007] The top of the vacuum falling body system is designed as an interface connected with the bottom of the laser interference system, and the bottom of the vacuum falling body system is designed as an interface connected with the upper support adjustment system and the lower support adjustment system.

[0008] The top of the vibration isolation system is designed as an interface connected with the bottom of the laser interference system, and the bottom of the vibration isolation system is designed as an interface connected with the upper support adjustment system and the lower support adjustment system.

[0009] The vacuum falling body system and the vibration isolation system have the same or similar heights, the positions are exchanged during erection, absolute gravity is measured by the vacuum falling body system at different erection positions, and the equivalent heights of the corresponding erection positions are measured and recorded, so that the measurement of gravity vertical gradient is realized.

[0010] Further, the vacuum falling body system comprises two first corner cube prisms arranged symmetrically, and the tip ends of the two first corner cube prisms are arranged in vertical opposition.

[0011] Further, the vibration isolation system comprises two second corner cube prisms arranged symmetrically, and the tip ends of the two second corner cube prisms are arranged in vertical opposition.

[0012] The application further provides a measurement method of the absolute gravity meter for measuring absolute gravity or gravity vertical gradient based on the above absolute gravity meter, comprising the following steps:

[0013] Step 1: first, erect the instrument in the order of the vacuum falling body system, the upper support adjustment system, the laser interference system, the vibration isolation system and the lower support adjustment system from top to bottom, at this time, the absolute gravity value gX at the high position is obtained. H H Step 2: then, erect the instrument in the order of the lower support adjustment system, the vibration isolation system, the laser interference system, the upper support adjustment system and the vacuum falling body system from top to bottom, at this time, the absolute gravity value gY at the low position is obtained.​

[0014] Step two: interchange the vacuum drop system and the vibration isolation system, and erect the instrument in the order of vibration isolation system, upper support adjustment system, laser interference system, vacuum drop system, and lower support adjustment system from top to bottom, at this time, the absolute gravity value g L at the low position X L is obtained.

[0015] Step three: the height value of the high position X H and its corresponding absolute gravity value g H , and the height value of the low position X L and its corresponding absolute gravity value g L are substituted into the following formula to obtain the vertical gradient γ of gravity.

[0016]

[0017] The above improved technical features can be combined with each other as long as they do not conflict with each other.

[0018] In general, compared with the prior art, in the absolute gravity instrument capable of measuring absolute gravity or the vertical gradient of gravity conceived by the present application, the vacuum drop system and the vibration isolation system are designed as interchangeable cavities with the same interface, so that the positions of the two systems are interchanged during the erection of the instrument in different measurement modes. The absolute gravity values at the high position and the low position are obtained in two measurement modes, and the effective heights of the drop corresponding to the two measurement modes are recorded, and the vertical gradient of gravity of the measurement point is calculated. Without an additional high-precision relative gravity instrument, high-precision measurement of the vertical gradient of gravity can be realized. Therefore, the present design does not require an additional high-precision relative gravity instrument, and only one absolute gravity instrument can realize high-precision absolute gravity measurement or vertical gradient of gravity measurement, greatly reducing the procurement and transportation costs, and the instrument structure is simple, easy to assemble and adjust, and has a wide range of applications. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a structural schematic diagram of the high position measurement mode of the present application.

[0020] Figure 2 is a structural schematic diagram of the vacuum drop system in the present application.

[0021] Figure 3 is a bottom view of the vacuum drop system in the present application.

[0022] Figure 4 is a structural schematic diagram of the drop prism mechanism in the present application.

[0023] Figure 5 is a structural schematic diagram of the vibration isolation system in the present application.

[0024] Figure 6 is the bottom view of the vibration isolation system in the present application.

[0025] Figure 7 is the structural schematic diagram of the vibration isolation mechanism in the present application.

[0026] Figure 8 is the structural schematic diagram of the reference prism mechanism in the present application.

[0027] Figure 9 is the structural schematic diagram of the laser interference system in the present application.

[0028] Figure 10 is the structural schematic diagram of the upper support adjustment system in the present application.

[0029] Figure 11 is the structural schematic diagram of the lower support adjustment system in the present application.

[0030] Figure 12 is the structural schematic diagram of the low position measurement mode in the present application.

[0031] In the figure: vacuum drop body system 1, first upper cover plate 11, first upper light transmission hole 12, vacuum drop body mechanism 13, drop body prism mechanism 131, inner cavity 132, support protrusion 133, third light transmission hole 134, first prism box 135, first pyramid prism 1353, frame body 136, support mechanism 137, transmission belt 138, transmission mechanism 139, second prism box 1310, first positioning pin 14, ion pump 15, driving motor 16, first lower cover plate 17, first lower light transmission hole 18, first positioning hole 19, laser interference system 2, vibration isolation system 3, second upper cover plate 31, second upper light transmission hole 32, vibration isolation mechanism 33, magnetic feedback device 331, support spring 333, reference prism mechanism 334, prism frame 3341, first reference prism cavity 3342, second pyramid prism 3343, annular pad plate 3344, fourth light transmission hole 3345, second reference prism cavity 3346, displacement sensing device 337, main spring 338, second lower cover plate 34, second lower light transmission hole 35, second positioning pin 36, second positioning hole 37, upper support adjustment system 4, lower support adjustment system 5, first pyramid prism group A, second pyramid prism group B. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] ReferenceFigures 1 to 12 An absolute gravimeter for measuring absolute gravity or gravity vertical gradient, comprising a vacuum falling body system 1, an upper support adjustment system 4, a laser interference system 2, a vibration isolation system 3 and a lower support adjustment system 5.

[0034] The top of the vacuum falling body system 1 is designed as an interface connected with the bottom of the laser interference system 2, and the bottom of the vacuum falling body system 1 is designed as an interface connected with the upper support adjustment system 4 and the lower support adjustment system 5.

[0035] The top of the vibration isolation system 3 is designed as an interface connected with the bottom of the laser interference system 2, and the bottom of the vibration isolation system 3 is designed as an interface connected with the upper support adjustment system 4 and the lower support adjustment system 5.

[0036] The vacuum falling body system 1 and the vibration isolation system 3 have the same or similar height, and the positions are interchangeable when erected. The vacuum falling body system 1 is used to measure absolute gravity at different erection positions, and the equivalent height of the corresponding erection position is measured and recorded, so as to realize the measurement of gravity vertical gradient.

[0037] The vacuum falling body system 1 is shown in Figures 2-3 The vacuum falling body system 1 is shown in

[0038] The vibration isolation system 3 is shown in Figures 5-6 The vibration isolation system 3 is shown in

[0039] The first upper cover plate 11 and the second upper cover plate 31 have the same size; the positions of the first upper light hole 12 and the first positioning pin 14 on the first upper cover plate 11 are the same as the positions of the second upper light hole 32 and the second positioning pin 36 on the second upper cover plate 31; and the first upper cover plate 11 and the second upper cover plate 31 can be matched with the bottom positioning hole of the laser interferometer 2 for positioning installation.

[0040] The first lower cover plate 17 and the second lower cover plate 34 have the same dimensions; the first lower light-transmitting hole 18 and the first positioning hole 19 are located on the first lower cover plate 17 and the second lower light-transmitting hole 35 and the second positioning hole 37 are located on the second lower cover plate 34; the second lower cover plate 17 and the second lower cover plate 34 can be matched with the positioning pins on the upper surface of the upper support adjustment system 4 and the lower support adjustment system 5 for positioning and installation.

[0041] The vacuum drop system 1 and the vibration isolation system 3 are at the same or similar heights, so that they will not affect other components of the instrument when they are replaced or installed.

[0042] Furthermore, the vacuum fall system 1 includes two symmetrically arranged first corner pyramid prisms 1353, with the tips of the two first corner pyramid prisms 1353 facing each other vertically.

[0043] The vacuum falling mechanism 13 is internally provided with a support mechanism 137, a transmission mechanism 139, two transmission belts 138 and a falling prism mechanism 131. One end of the transmission mechanism 139 is connected to the output shaft of the drive motor 16 and the other end is connected to the two transmission belts 138. The falling prism mechanism 131 moves up and down through the two transmission belts 138.

[0044] The falling prism mechanism 131 is as follows Figure 4 As shown, the device includes a frame 136, a first prism box 135, and a second prism box 1310. The first prism box 135 and the second prism box 1310 form a first pyramidal prism group A. The frame 136 is connected to two transmission belts 138. The first prism box 135 and the second prism box 1310 are symmetrically arranged in the inner cavity 132 of the frame 136. The first prism box 135 and the second prism box 1310 have the same structure. Two sets of support protrusions 133 are arranged at the top and bottom of the inner cavity 132. The top of the upper set of support protrusions 133 can position and support the first prism box 135, and the top of the lower set of support protrusions 133 can position and support the second prism box 1310. A third light-transmitting hole 134 is opened at the top and bottom of the frame 136.

[0045] Furthermore, the vibration isolation system 3 includes two symmetrically arranged second corner pyramid prisms 3343, with the tips of the two second corner pyramid prisms 3343 facing each other vertically.

[0046] The vibration isolation mechanism 33 is as follows Figure 7 As shown, it includes a support spring 333, a main spring 338, a reference prism mechanism 334, a displacement sensing device 337, and a magnetic feedback device 331.

[0047] The reference prism mechanism 334, as described above Figure 8As shown, the device includes a prism frame 3341, a first reference prism cavity 3342, and a second reference prism cavity 3346. The first reference prism cavity 3342 and the second reference prism cavity 3346 are symmetrically arranged on the inner wall of the prism frame 3341. The first reference prism cavity 3342 and the second reference prism cavity 3346 are symmetrically arranged about the cross-section of the prism frame 3341. The first reference prism cavity 3342 and the second reference prism cavity 3346 have the same structure. A second pyramidal prism 3343 is placed in each prism cavity 3346. The tips of the two second pyramidal prisms 3343 are arranged vertically opposite each other to form a second pyramidal prism group B. A fourth light-transmitting hole 3345 is provided at the top and bottom of the prism frame 3341. Annular pads 3344 are provided on the inner walls of the first reference prism cavity 3342 and the second reference prism cavity 3346 on one side of the tip of the second pyramidal prism 3343. The annular pads 3344 are fixed to the second pyramidal prism 3343.

[0048] A preferred embodiment of the present invention provides a method for measuring absolute gravity or the vertical gradient of gravity based on the aforementioned absolute gravimeter, comprising the following steps:

[0049] Step 1: First, set up the instrument in the following order from top to bottom: vacuum drop system 1, upper support adjustment system 4, laser interferometry system 2, vibration isolation system 3, and lower support adjustment system 5. At this time, obtain the X-ray at the high position. H absolute gravity value g H ;

[0050] like Figure 1 As shown, the instrument is set up in the following order from top to bottom: vacuum drop system 1, upper support adjustment system 4, laser interference system 2, vibration isolation system 3, and lower support adjustment system 5. Vacuum drop system 1 is located above laser interference system 2, and vibration isolation system 3 is located below laser interference system 2. The test beam, split by laser interference system 2, ascends vertically through the first lower light-transmitting hole 18 at the bottom of vacuum drop system 1. It is reflected by the first pyramidal prism 1353 in the vertically downward-pointing second prism box 1310 of vacuum drop system 1 and returns through the first lower light-transmitting hole 18, then descends through laser interference system 2 to reach vibration isolation system 3. The test beam continues downward through the second upper light-transmitting hole 32 at the top of vibration isolation system 3. It is reflected by the second pyramidal prism 3343 in the vertically upward-pointing first reference prism cavity 3342 of vibration isolation system 3 and returns through the second upper light-transmitting hole 32 to laser interference system 2. After passing through other mirrors in the laser interference system, it re-merges with the reference beam. At this point, the X-ray at a high position is obtained. H absolute gravity value g H ;

[0051] Step Two: Next, swap the positions of the vacuum drop system 1 and the vibration isolation system 3, and set up the instrument in the following order from top to bottom: vibration isolation system 3, upper support adjustment system 4, laser interferometry system 2, vacuum drop system 1, and lower support adjustment system 5. At this point, obtain the X-ray at the low position. L absolute gravity value g L ;

[0052] like Figure 12 As shown, the instrument is set up in the following order from top to bottom: vibration isolation system 3, upper support adjustment system 4, laser interferometry system 2, vacuum drop system 1, and lower support adjustment system 5. Vibration isolation system 3 is located above laser interferometry system 2, and vacuum drop system 1 is located below laser interferometry system 2. The test beam, split by laser interferometry system 2, ascends vertically through the second lower light-transmitting hole 35 at the bottom of vibration isolation system 3. It is then reflected by the second pyramidal prism 3343 in the second reference prism cavity 3346 (vertically downward) within vibration isolation system 3, returns through the second lower light-transmitting hole 35, and descends through laser interferometry system 2 to reach vacuum drop system 1. The test beam then continues downward through the first upper light-transmitting hole 12 at the top of vacuum drop system 1. It is reflected by the first pyramidal prism 1353 in the first prism box 135 (vertically upward) within vacuum drop system 1, returns through the first upper light-transmitting hole 12 to laser interferometry system 2, and re-merges with the reference beam after passing through other reflectors in laser interferometry system 2. At this point, the X-ray at the low position is obtained. L absolute gravity value g L ;

[0053] Step 3: X at the high position H The height value and its corresponding absolute gravity value g H and X at low position L The height value and its corresponding absolute gravity value g L Substituting these values ​​into the following formula yields the vertical gradient of gravity γ.

[0054]

[0055] The mechanical shape, hole size and form in the preferred embodiments of the present invention are not limited to be consistent with the embodiments, but only their functional features are limited.

[0056] The absolute gravimeter of this invention, used for measuring absolute gravity and the vertical gradient of gravity, has a simple structure and is easy to operate. By designing the aforementioned measurement mode and corresponding mechanical structure, the instrument's inherent characteristics can be utilized more effectively. In addition to measuring absolute gravity values, it can measure the vertical gradient of gravity at the measurement point without the need for an additional high-precision relative gravimeter. Compared to traditional absolute gravimeters, it offers wider applicability and greater economic efficiency. This invention improves the efficiency and cost-effectiveness of field gravity measurement operations, and has promising application prospects and widespread application value.

[0057] The above description is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiment, but any equivalent modification or change made by those skilled in the art according to the disclosed content of the present application should be included in the protection scope recorded in the claims.

Claims

1. An absolute gravimeter for measuring absolute gravity or a vertical gradient of gravity, characterized by: The vacuum falling body system (1), the upper support adjusting system (4), the laser interference system (2), the vibration isolation system (3) and the lower support adjusting system (5); The top of the vacuum falling body system (1) is designed as an interface connected with the bottom of the laser interference system (2), and the bottom of the vacuum falling body system (1) is designed as an interface connected with the upper support adjusting system (4) and the lower support adjusting system (5); The top of the vibration isolation system (3) is designed as an interface connected with the bottom of the laser interference system (2), and the bottom of the vibration isolation system (3) is designed as an interface connected with the upper support adjusting system (4) and the lower support adjusting system (5); The vacuum falling body system (1) and the vibration isolation system (3) have the same or similar height, and the positions are exchanged when being erected, the absolute gravity is measured by the vacuum falling body system (1) at different erection positions, and the equivalent height of the corresponding erection position is measured and recorded, so that the measurement of the vertical gradient of gravity is realized.

2. An absolute gravimeter for measuring absolute gravity or a vertical gradient of gravity according to claim 1, characterized in that: The vacuum falling body system (1) comprises two first corner cube prisms (1353) arranged symmetrically, and the tip ends of the two first corner cube prisms (1353) are arranged in a vertical opposite manner.

3. An absolute gravimeter for measuring absolute gravity or a vertical gravity gradient according to claim 1 or 2, characterized in that: The vibration isolation system (3) comprises two second corner cube prisms (3343) arranged symmetrically, and the tip ends of the two second corner cube prisms (3343) are arranged in a vertical opposite manner.

4. The measurement method of an absolute gravimeter for measuring absolute gravity or a vertical gradient of gravity according to claim 1, characterized by: The method comprises the following steps: The vacuum falling body system (1), the upper support adjusting system (4), the laser interference system (2), the vibration isolation system (3) and the lower support adjusting system (5); Step one: first according to from top to bottom in turn for vacuum falling body system (1), upper support adjusting system (4), laser interference system (2), vibration isolation system (3), lower support adjusting system (5) erect instrument, at this time, obtain the absolute gravity value g H of high position X H ; Step two: the vacuum falling body system (1), vibration isolation system (3) position interchange, from top to bottom in turn for vibration isolation system (3), the upper support adjustment system (4), laser interference system (2), vacuum falling body system (1), the lower support adjustment system (5) erection instrument, at this time, the low position X L The absolute value of gravity g L ; Step three: Substitute the height value of high position X H and its corresponding absolute gravity value g H and the height value of low position X L and its corresponding absolute gravity value g L into the following formula to obtain the vertical gradient of gravity γ;

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