A double-falling-body absolute gravimeter

Abstract

The present invention discloses a dual-falling absolute gravimeter and a testing method. The dual-falling absolute gravimeter includes a bracket, a laser interferometer, two vacuum falling chambers, and a data collector. The laser interferometer is installed on the bracket. The two vacuum falling chambers are respectively arranged above and below the laser interferometer. At one end of the two vacuum falling chambers close to each other, there are perspective windows capable of transmitting light beams, and inside both of them, there are prisms that can freely fall relative to their chambers. The laser interferometer is used to respectively emit vertical light beams to the perspective windows of the two vacuum falling chambers and respectively receive the light beams reflected by the two prisms. The data collector is electrically connected to the laser interferometer and is used to collect the difference in the falling distances of the two prisms measured by the laser interferometer. Advantages: This device eliminates the ultra-low frequency vibration isolation device with the most complex structure in the traditional absolute gravimeter, and solves the technical problem that the existing absolute gravimeter is affected by ground vibration and the measurement accuracy is affected.

Description

Technical Field

[0001] The present invention relates to the technical field of gravity testing, and particularly relates to a double-falling absolute gravimeter. Background Art

[0002] Traditional absolute gravimeters all use the method of free fall plus optical interference to measure the gravitational acceleration g. The test optical path contains a test prism and a reference prism. During the measurement, the test prism makes a free fall motion and is not affected by vibration; however, the reference prism will be affected by vibration, causing changes in the test optical path and interfering with the measurement. Therefore, corresponding stabilization measures must be taken for the reference prism to suppress vibration interference. The vibration sources affecting the reference prism mainly include ground pulsation and human activities, etc. Human activities are easy to isolate due to their relatively high frequencies, but the ground pulsation components are very rich, mainly manifested as a wide frequency band, a large amplitude range, etc. The current vibration isolation technology is difficult to completely isolate it. Therefore, it is impossible to ensure that the reference prism is in an absolutely static state, and it is impossible to completely eliminate the interference caused by vibration during the test. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a double-falling absolute gravimeter and a test method, which effectively overcome the defects of the prior art.

[0004] The technical solution of the present invention to solve the above technical problem is as follows:

[0005] Provide a double-falling absolute gravimeter, including a support, a laser interferometer, two vacuum falling chambers, and a data collector. The above laser interferometer is installed on the above support. The two above vacuum falling chambers are respectively arranged above and below the above laser interferometer. The relatively close ends of the two above vacuum falling chambers are both provided with perspective windows capable of transmitting light beams, and both of them have prisms that can freely fall relative to their chambers. The above laser interferometer is used to respectively emit vertical light beams to the perspective windows of the two above vacuum falling chambers, and respectively receive the light beams reflected by the two above prisms. The above data collector is electrically connected to the above laser interferometer and is used to collect the difference in the falling distances of the two prisms measured by the laser interferometer.

[0006] The beneficial effect of the present invention is: The most complex ultra-low frequency vibration isolation device in the traditional absolute gravimeter is removed, and the technical problem that the existing absolute gravimeter is affected by ground vibration and the measurement accuracy is solved.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Further, the above support includes a tabletop and at least three vertical legs that are spaced apart and assembled at the lower end of the tabletop. The above laser interferometer is installed on the upper end of the above tabletop, and the two above vacuum falling chambers are respectively installed on the above laser interferometer and the lower end of the above tabletop.

[0009] The beneficial effect of adopting the above further solution is that the support structure is simple, the various components are arranged reasonably, and the asynchronous falling of the two prisms can be smoothly carried out.

[0010] Furthermore, the lower ends of the above-mentioned legs are respectively equipped with supporting structures for adjusting the heights thereof.

[0011] The beneficial effect of adopting the above further solution is that it is easy to adjust the height of the table to adapt to the conditions required for device testing, and it can ensure that the entire table remains level, thereby ensuring accurate test results.

[0012] Furthermore, the vacuum drop chamber includes a closed chamber body, a placement table and a moving mechanism. The chamber body is connected to an ion pump for evacuating the interior thereof. The placement table is placed at a position in the chamber body corresponding to the perspective window, and has upper and lower light-transmitting windows thereon. The prism is placed in the upper window area of ​​the placement table. The moving mechanism is transmission-connected to the placement table for driving the placement table to move vertically up and down in the chamber body.

[0013] The beneficial effects of adopting the above further solution are reasonable design and convenient operation and use.

[0014] Furthermore, the moving mechanism includes a motor, a conveyor belt, a driving wheel and a driven wheel. The motor is installed at the lower end of the side wall of the warehouse body, and its driving shaft extends horizontally into the interior of the warehouse body. The driving wheel is coaxially assembled on one end of the driving shaft extending into the warehouse body. The driven wheel is rotatably installed at the upper end of the interior of the warehouse body corresponding to the position of the driving wheel. The conveyor belt wraps around the driving wheel and the driven wheel. The placing platform is placed in front of the conveyor belt and is fixedly connected to the belt body on the front side of the conveyor belt.

[0015] The beneficial effect of adopting the above further solution is that the moving mechanism is reasonably designed, simple and convenient to operate, and can ensure the effective movement of the placement table, thereby achieving a good free fall of the prism.

[0016] Furthermore, the moving mechanism further comprises a guide rail assembly, which is vertically mounted in the bin body, and the placement table is mounted on the guide rail assembly so as to be slidable up and down.

[0017] The beneficial effect of adopting the above further solution is that the design facilitates the placement table to move up and down smoothly and well. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the double-falling-body absolute gravimeter of the present invention;

[0019] In the accompanying drawings, the components represented by the reference numerals are listed as follows:

[0020] 1. Support, 2. Laser interferometer, 3. Vacuum free-fall chamber, 4. Data collector, 5. Controller, 11. Tabletop, 12. Leg, 31. Chamber body, 32. Placing table, 33. Ion pump, 34. Motor, 35. Prism, 121. Support structure. Detailed implementation mode

[0021] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0022] Example: As Figure 1 shown, the double-free-fall absolute gravimeter of this embodiment includes a support 1, a laser interferometer 2, two vacuum free-fall chambers 3 and a data collector 4. The above laser interferometer 2 is installed on the above support 1. The two above vacuum free-fall chambers 3 are respectively arranged above and below the above laser interferometer 2. Perspective windows capable of transmitting light beams are provided at the relatively close ends of the two above vacuum free-fall chambers 3, and prisms 35 that can freely fall relative to their chamber bodies are provided inside both of them. The above laser interferometer 2 is used to respectively emit vertical light beams to the perspective windows of the two above vacuum free-fall chambers 3, and respectively receive the light beams reflected by the two above prisms 35. The above data collector 4 is electrically connected to the above laser interferometer 2 and is used to collect the difference in the falling distances of the two prisms 35 measured by the laser interferometer 2.

[0023] More specifically, the laser interferometer 2 uses a conventional instrument on the market, and the distribution of its internal optical components is slightly adjusted. As Figure 1 shown in the figure, it includes a beam expander 21, a beam splitter 22, a beam combiner 23, a beam displacer 24, a photodiode 25, a second reflector 26 and a first reflector 27. The beam splitter 22 is used to split two beams of light upward and downward, and receive the vertical light beam reflected downward from the upper prism 35. The beam expander 21 is used to emit a beam of light to the beam splitter 22. The first reflector 27 is used to receive the vertical light beam reflected upward by the lower prism 35. The beam displacer 24 is used to receive the light beam reflected to it by the first reflector 27, and transmit it to the second reflector 26, and then the second reflector 26 reflects it to the beam combiner 23. The beam combiner 23 combines the two reflected light beams into one beam of light and emits it to the photodiode 25 for reception.

[0024] The test method includes the following steps:

[0025] S1. Pre-move the prisms 35 in the two vacuum free-fall chambers 3 upward in the chambers to their respective free-fall initial positions;

[0026] S2. Turn on the laser interferometer 2. First, make the prism 35 in the lower vacuum free-fall chamber 3 freely fall, and record its free-fall time. When it has fallen for a certain time and the free-fall process has not ended, make the prism 35 in the upper vacuum free-fall chamber 3 freely fall;

[0027] S3. The falling distance difference S between the two prisms 35 collected by the data collector 4 at any time point during the free-fall stage B-A and the corresponding time are used to calculate the absolute gravity difference g using the following formula A0 :

[0028]

[0029] where t1 is the initial time point of free fall of the upper prism 35, t2 is the end time point of free fall of the lower prism 35, l is the height distance difference between the two prisms 35 at their initial positions, and γ is the vertical gravity gradient value;

[0030] Compared with the prior art, the present invention has the following advantages and positive effects:

[0031] ① The most complex ultra-low frequency vibration isolation device in the traditional absolute gravimeter is removed;

[0032] ② Two corner cube prisms fall freely successively. Both corner cube prisms are in a free-fall state and are independent of ground vibration, fundamentally solving the technical problem that the measurement accuracy of the existing absolute gravimeter is affected by ground vibration.

[0033] As a preferred embodiment, the above-mentioned bracket 1 includes a tabletop 11 and at least three vertical legs 12 that are spaced apart and assembled at the lower end of the tabletop 11. The above-mentioned laser interferometer 2 is installed at the upper end of the above-mentioned tabletop 11, and the two above-mentioned vacuum free-fall chambers 3 are respectively installed on the above-mentioned laser interferometer 2 and at the lower end of the above-mentioned tabletop 11. More specifically, the tabletop 11 can be a hollow triangular frame tabletop or a transparent disc-shaped tabletop to facilitate the smooth passage of light beams.

[0034] Preferably, the lower ends of the above-mentioned legs 12 are respectively equipped with support structures 121 for adjusting their heights, which is beneficial to adjusting the height of the tabletop 11 to a height convenient for testing.

[0035] The above-mentioned support structure 121 generally uses a conventional adjusting screw column on the market. Of course, it can also be other products or structures with similar effects.

[0036] As a preferred embodiment, the vacuum drop chamber 3 includes a closed chamber body 31, a placement table 32 and a moving mechanism. The chamber body 31 is connected to an ion pump 33 for evacuating the interior thereof. The placement table 32 is placed in a position corresponding to the perspective window in the chamber body 31, and has upper and lower light-transmitting windows thereon. The prism 35 is placed in the upper window area of ​​the placement table 32. The moving mechanism is transmission-connected to the placement table 32 to drive the placement table 32 to move vertically up and down in the chamber body 31. During the test, the placement table 32 and the prism 35 are moved to the initial position of the free fall in advance through the moving mechanism. Before the free fall, the placement table 32 is quickly moved downward through the moving mechanism (the moving speed of the placement table 32 is greater than the free fall speed of the prism 35), so that the prism 35 can have a good free fall. The design is reasonable and the operation is convenient and simple.

[0037] The best design of the bin body 31 is a cylindrical bin body, and the two bin bodies 31 are coaxially arranged.

[0038] More preferably, the moving mechanism includes a motor 34, a conveyor belt, a driving wheel and a driven wheel. The motor 34 is installed at the lower end of the side wall of the warehouse body 31, and its driving shaft extends horizontally into the interior of the warehouse body 31. The driving wheel is coaxially assembled on one end of the driving shaft extending into the warehouse body 31. The driven wheel is rotatably installed at the upper end of the interior of the warehouse body 31 corresponding to the position of the driving wheel. The conveyor belt wraps around the driving wheel and the driven wheel. The placement table 32 is placed on the front side of the conveyor belt and is fixedly connected to the belt body on the front side of the conveyor belt. During operation, the motor 34 drives the driving wheel to rotate rapidly, thereby driving the belt to rotate and driving the placement table 32 to move rapidly. It has a simple design, is easy to operate and use, and runs relatively smoothly.

[0039] It also includes a controller 5 , which is connected to the laser interferometer 2 as a control system of the laser interferometer 2 . Of course, the controller 5 can also be connected to the above-mentioned moving mechanism and ion pump 33 to control the operation of the vacuum drop chamber 3 .

[0040] As a preferred embodiment, the moving mechanism further includes a guide rail assembly, which is vertically mounted in the bin body 31, and the placement table 32 is slidably mounted on the guide rail assembly. The design of the guide rail assembly enables the placement table 32 to move well in the vertical direction without any skewing or obstruction to the free fall of the prism 35.

[0041] The guide rail assembly generally includes two vertical guide rods spaced apart from each other. Holes are provided on both sides of the placement platform 32 for the guide rods to pass through, or the placement platform 32 is connected to the two guide rods by means of a slider that is slidably matched with the two guide rods.

[0042] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A double-falling absolute gravimeter, characterized in that: The invention comprises a support (1), a laser interferometer (2), two vacuum drop chambers (3) and a data acquisition device (4), wherein the laser interferometer (2) is mounted on the support (1), and the two vacuum drop chambers (3) are respectively arranged above and below the laser interferometer (2); the two vacuum drop chambers (3) are provided with a perspective window capable of transmitting a light beam at one end that is relatively close to the other, and both of them have a prism (35) inside that can freely fall relative to the chamber body; the laser interferometer (2) is used to respectively transmit light beams to the two vacuum drop chambers. The perspective window of (3) emits a vertical light beam and receives the light beams reflected by the two prisms (35) respectively; the data collector (4) is electrically connected to the laser interferometer (2) and is used to collect the difference in falling distances of the two prisms (35) measured by the laser interferometer (2); the vacuum drop chamber (3) comprises a closed chamber body (31), a placement table (32) and a moving mechanism; the chamber body (31) is connected to an ion pump (33) for evacuating the interior thereof; the placement table (32) is placed on the chamber body ( The prism (35) is placed in the window area at the upper end of the placement platform (32), and the moving mechanism is connected to the placement platform (32) in a transmission manner, and is used to drive the placement platform (32) to move vertically up and down in the warehouse body (31); the moving mechanism includes a motor (34), a conveyor belt, a driving wheel and a driven wheel, and the motor (34) is installed at the lower end of the side wall of the warehouse body (31), and its driving shaft extends horizontally into the interior of the warehouse body (31). The driving wheel is coaxially mounted on one end of the driving shaft extending into the warehouse body (31); the passive wheel is rotatably mounted on the upper end of the warehouse body (31) at a position corresponding to the driving wheel; the conveyor belt surrounds the driving wheel and the passive wheel; the placement platform (32) is placed in front of the conveyor belt and is connected and fixed to the belt body on the front side of the conveyor belt; the moving mechanism also includes a guide rail assembly, the guide rail assembly is vertically mounted in the warehouse body (31), and the placement platform (32) is slidably mounted on the guide rail assembly up and down; The test method includes the following steps: S1, moving the prisms (35) in the two vacuum drop chambers (3) upwards in advance to their respective initial drop positions; S2, turning on the laser interferometer (2), firstly making the prism (35) in the lower vacuum drop chamber (3) fall freely, and recording its falling time, and when it has fallen for a certain time and has not yet finished falling, making the prism (35) in the upper vacuum drop chamber (3) fall freely; S3. The falling distance difference S between the two prisms (35) collected by the data collector (4) at any time point when both are in the free-fall stage B-A and the corresponding time t are used to calculate the absolute gravity difference g by the following formula A0 : Formula (1), Wherein, t1 is the initial time point of the free fall of the upper prism (35), l is the height distance difference between the two prisms (35) at their initial positions, and γ is the vertical gravity gradient value.

2. The double-falling absolute gravimeter according to claim 1, wherein: The bracket (1) includes a tabletop (11) and at least three vertical legs (12) that are spaced apart and assembled at the lower end of the tabletop (11). The laser interferometer (2) is installed at the upper end of the tabletop (11), and the two vacuum free-fall chambers (3) are respectively installed on the laser interferometer (2) and the lower end of the tabletop (11).

3. A dual-falling absolute gravimeter according to claim 2, characterized in that: Support structures (121) for adjusting their heights are respectively assembled at the lower ends of the legs (12).

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