A kind of coal mine underground laser measurement aperture device and method

Abstract

The application discloses a kind of coal mine underground laser measuring aperture device and method, including measuring device, push rod, data line and display;Measuring device includes outer tube, center axis, support I, laser, receiving lens, support II, photoelectric coupling element and range tube;The distance between the light spot on photoelectric coupling element and the main optical axis of receiving lens is obtained by laser, receiving lens and photoelectric coupling element combination, then the aperture is obtained according to the principle of similar triangle, etc., in combination with the fixed parameter measured in advance.The present application can accurately measure aperture, solve the problems of insufficient applicability, large volume and high price of current coal mine underground gas extraction drilling aperture measurement equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of underground coal mine gas extraction, and relates to a coal mine underground laser measuring aperture device and method. BACKGROUND

[0002] Coal mine gas extraction is an important means to prevent gas overrun, and construction of gas extraction boreholes is a main form of coal mine gas control. The gas extraction borehole is formed by rotating a drill bit driven by a drilling machine in a coal seam. The gas existing in the coal seam enters the borehole through desorption, the borehole is connected to a special gas extraction pipeline, and the purpose of gas extraction is achieved by adjusting the negative pressure. Therefore, the borehole quality is an important factor that cannot be ignored in gas extraction. Most coal mines in China have large gas pressure, large ground stress, and soft coal seams, and after the borehole is constructed, the borehole is severely deformed or even collapses. How to accurately grasp the real data of the aperture of the constructed borehole is of great significance for analyzing the stability of the stratum, the degree of fracture development, and the attenuation of gas flow.

[0003] At present, the methods for measuring the aperture in the coal mine underground are as follows: one is to refer to the size of the drill bit, which is based on the premise that the borehole is not deformed, and is suitable for complete and stable strata; the other is to use geophysical logging related instruments and equipment to calculate the aperture through electrical and electromagnetic wave parameters, which is mainly used in oil and gas drilling and surface drilling, and the defects are that the equipment is large in size and expensive, and has insufficient applicability in the limited space of the coal mine underground. Therefore, a new type of aperture measuring device is needed in the coal mine underground to solve the limitations of the existing methods and accurately grasp the characteristics of the stratum to provide guidance for subsequent borehole construction. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a coal mine underground laser measuring aperture device and method to solve the problems of insufficient applicability, large size, and high price of the aperture measuring equipment for the coal mine underground gas extraction borehole.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] A coal mine underground laser measuring aperture device, comprising a diameter measuring device, a push rod, a data line, and a display.

[0007] The diameter measuring device includes an outer cylinder, a central shaft, bracket I, lasers, receiving lenses, bracket II, optocouplers, and a measuring tube. The central shaft is positioned along the inner axis of the outer cylinder, with one end fixed to the center of the inner wall of the outer cylinder end cap. Bracket I is fixed to the central shaft in the middle, with each of its three ends connected to a laser. The three lasers are close to the inner wall of the outer cylinder and distributed at 120° intervals. The receiving lens is embedded in the side wall of the outer cylinder, with the three receiving lenses distributed at 120° intervals, and the principal optical axis of each receiving lens perpendicular to the central axis of the outer cylinder. Bracket II is positioned on the central shaft in the middle, with each of its three ends connected to an optocoupler. The three optocouplers are distributed at 120° intervals. ° distribution; each laser, a receiving lens, and an optocoupler form a diameter measuring unit. In each diameter measuring unit, the line connecting the laser and the receiving lens is parallel to the central axis of the outer cylinder. The laser emitted by the laser can pass through the through hole on the outer cylinder, hit the hole wall, and then be reflected to the receiving lens. The principal optical axis of the receiving lens is perpendicular to its corresponding optocoupler, and the distance between the optical center of the receiving lens and the optocoupler is the focal length of the receiving lens. The front edge of the optocoupler is flush with the optical center of the receiving lens. The laser transmitted through the receiving lens can be imaged on the optocoupler and form a light spot. The range tube is sleeved on the central axis and located between the laser and the optocoupler.

[0008] The end of the push rod is connected to the outer cylinder end cap of the diameter measuring device; one end of the data cable passes through the push rod and is connected to the diameter measuring device, and the other end is connected to the display.

[0009] The present invention also includes the following technical features:

[0010] Specifically, the laser emitted by the laser makes a 45° angle with the central axis of the outer cylinder.

[0011] Specifically, the laser includes a protective cover, a light-emitting diode, a focusing lens, and a light-emitting port.

[0012] Specifically, the receiving lens is embedded in a long strip-shaped through hole in the side wall of the outer cylinder so that the position of the receiving lens can be adjusted along the axial direction of the outer cylinder.

[0013] Specifically, the position of the bracket II on the central axis is adjustable to adjust the axial position of the optocoupler.

[0014] Specifically, the outer cylinder sidewall is provided with a side opening, which is opposite to the measuring tube, so as to adjust the measuring range of the measuring tube.

[0015] A method for measuring the aperture of an underground laser aperture measuring device in a coal mine, comprising the following steps:

[0016] Step 1: After passing the push rod through the data cable, fix it to the diameter measuring device. Slowly push it into the hole from the orifice. Connect multiple push rods in sequence until the hole depth to be measured is reached. Record the distance between the laser output port and the optical center of the receiving lens, the outer cylinder radius of the diameter measuring device, the angle between the laser and the central axis, and the focal length of the receiving lens.

[0017] Step 2: Connect the power supply, turn on the monitor, supply power to the diameter measuring device inside the hole via the data cable, and the laser emits a laser beam;

[0018] Step 3: The laser beam enters the borehole. The laser beams emitted by the three lasers are reflected at points A, B, and C on the inner wall of the borehole. The reflected light beams enter the three receiving lenses and are focused to form images on the three optocouplers, forming a light spot on each optocoupler. The distance between the light spot and the front edge of the optocoupler is obtained, which is the distance between the light spot and the principal optical axis of the receiving lens.

[0019] The borehole diameter measured by the caliper is:

[0020]

[0021] In the above formula, the distances from points A, B, and C to the central axis of the diameter measuring device are a, b, and c, respectively; a = y1 + r, b = y2 + r, c = y3 + r, where y1 is the distance between point A and the outer wall of the diameter measuring device, y2 is the distance between point B and the outer wall of the diameter measuring device, y3 is the distance between point C and the outer wall of the diameter measuring device, and r is the radius of the diameter measuring device.

[0022] Specifically, the distance y1 between point A and the outer wall of the caliper is obtained by solving the following equations simultaneously:

[0023]

[0024] y1=(l-x1′)tanθ

[0025] Where x1 is the distance between the light spot formed by the receiving lens on the optocoupler at point A and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, and l is the distance between the laser output port and the optical center of the receiving lens. ′ Let θ be the distance between point A and the principal optical axis of the receiving lens, and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

[0026]

[0027] Specifically, the distance y2 between point B and the outer wall of the caliper is obtained by solving the following equations simultaneously:

[0028]

[0029] y2=(l-x2′)tanθ

[0030] Where x2 is the distance between the light spot formed by the receiving lens on the optocoupler at point B and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, l is the distance between the laser output port and the optical center of the receiving lens, x2′ is the distance between point B and the principal optical axis of the receiving lens, and θ is the angle between the laser and the central axis of the diameter measuring device; The above two equations are combined to obtain...

[0031]

[0032] Specifically, the distance y3 between point C and the outer wall of the diameter measuring device is obtained by solving the following equations simultaneously:

[0033]

[0034] y3=(l-x3′)tanθ

[0035] Where x3 is the distance between the light spot formed by the receiving lens on the optocoupler at point C and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, l is the distance between the laser output port and the optical center of the receiving lens, x3′ is the distance between point C and the principal optical axis of the receiving lens, and θ is the angle between the laser and the central axis of the diameter measuring device; The above two equations are combined to obtain...

[0036]

[0037] Compared with the prior art, the present invention has the following technical effects:

[0038] (1) The present invention is small in size and highly applicable. The side length of the display is only 160mm and the radius of the diameter measuring device is only 20mm. It is suitable for the narrow space in the coal mine and is easy to store and transport.

[0039] (2) The present invention has a large measuring range (40-400mm), which can meet the requirements of current conventional downhole gas extraction boreholes. Exploration and drainage drilling Explosive drilling Core drilling Aperture measurement.

[0040] (3) The present invention takes into account the offset factor of the diameter measuring device, and the measurement data is closer to the actual value. The measured distance data is converted by using the principle of three points being concyclic, so as to ensure that the final displayed aperture is closer to the actual aperture of the measuring point.

[0041] (4) Based on the measured borehole diameter, this invention can draw the borehole spatial shape by combining parameters such as the depth of the push rod, the inclination angle, and the azimuth angle, providing an effective method for understanding borehole deformation and determining the location of borehole collapse.

[0042] (5) The present invention has a simple structure and low cost. The core component, the diameter measuring device, uses simple optical and mathematical principles. The internal laser, lens, optocoupler, etc. have also been researched and matured and can be applied in a modular manner. Therefore, the cost of the present invention is controllable and has broad market application prospects. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0044] Figure 2 This is a schematic diagram of the diameter measuring device of the present invention;

[0045] Figure 3 This is a schematic diagram of the laser structure of the present invention;

[0046] Figure 4 This is a schematic diagram of the arrangement of the three lasers in this invention;

[0047] Figure 5 This is a schematic diagram of the arrangement of the receiving lens and optocoupler element of the present invention;

[0048] Figure 6 This is a diagram of a monitor;

[0049] Figure 7 This is a schematic diagram of similar triangles;

[0050] Figure 8 This is a schematic diagram illustrating the principle of aperture calculation.

[0051] The meanings of the labels in the diagram are as follows:

[0052] 1. Diameter measuring device; 2. Push rod; 3. Data cable; 4. Display; 5. Hole wall; 11. Outer cylinder; 12. Central shaft; 13. Support I; 14. Laser; 15. Receiving lens; 16. Support II; 17. Optocoupler; 18. Range tube; 141. Protective cover; 142. Light-emitting diode; 143. Condensing lens; 144. Light outlet; 171. Photosensitive unit; 172. Circuit layer; 41. Explosion-proof housing; 42. Display screen; 43. Parameter display area; 44. Power interface; 45. Data cable interface. Detailed Implementation

[0053] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0054] Example 1:

[0055] like Figures 1 to 6 As shown, this embodiment provides a laser aperture measuring device for underground coal mines, including a diameter measuring device 1, a push rod 2, a data cable 3, and a display 4.

[0056] The diameter measuring device 1 includes an outer cylinder 11, a central shaft 12, a bracket I13, a laser 14, a receiving lens 15, a bracket II16, an optocoupler 17, and a measuring tube 18. In this embodiment, the diameter measuring device 1 has an overall length of 100mm and a diameter of 20mm. The receiving lens is a convex lens with a focal length f = 10mm. The central shaft 12 is arranged at the central axis position inside the outer cylinder 11, and one end of the central shaft 12 is fixed to the center of the inner wall of the end cap of the outer cylinder 11. The bracket I13 is fixed in the middle on the central shaft 12, and each of the three ends of the bracket I13 is connected to a laser 14. The three lasers 14 are close to the inner wall of the outer cylinder 11 and are distributed at 120° to each other. The receiving lens 15 is embedded in the side wall of the outer cylinder 11. The three receiving lenses 15 are distributed at 120° to each other, and the principal optical axis of each receiving lens 15 is perpendicular to the central axis of the outer cylinder 11. The bracket II16 is located in the middle on the central shaft 12. Each of the three ends is connected to an optocoupler 17, and the three optocouplers 17 are distributed at 120° to each other. Each laser 14, a receiving lens 15, and an optocoupler 17 form a diameter measuring unit. In each diameter measuring unit, the line connecting the laser 14 and the receiving lens 15 is parallel to the central axis of the outer cylinder 11. The laser emitted by the laser 14 can pass through the through hole on the outer cylinder 11 and hit the hole wall, and then be reflected to the receiving lens 15. The principal optical axis of the receiving lens 15 is perpendicular to its corresponding optocoupler 17, and the distance between the optical center of the receiving lens 15 and the optocoupler 17 is the focal length of the receiving lens 15. The front edge of the optocoupler 17 is flush with the optical center of the receiving lens 15. The laser energy passing through the receiving lens 15 can be imaged on the optocoupler 17 and form a light spot. The range tube 18 is sleeved on the central axis 12 and located between the laser 14 and the optocoupler 17.

[0057] The end of the push rod 2 is connected to the outer cylinder end cap of the diameter measuring device 1; one end of the data cable 3 passes through the push rod 2 and is connected to the diameter measuring device 1, and the other end is connected to the display 4.

[0058] The laser emitted by laser 14 forms a 45° angle with the central axis of outer cylinder 11.

[0059] The laser 14 includes a protective cover 141, a light-emitting diode 142, a focusing lens 143, and a light-emitting port 144.

[0060] The receiving lens 15 is embedded in the elongated through hole on the side wall of the outer cylinder 11 so that the position of the receiving lens 15 can be adjusted along the axial direction of the outer cylinder 11.

[0061] The position of bracket II16 on the central axis 12 is adjustable to adjust the axial position of optocoupler 17.

[0062] The outer cylinder 11 has a side opening on its side wall, which is opposite to the measuring tube 18 to adjust the measuring range of the measuring tube 18. In this embodiment, the side opening has a cross-sectional length of 40mm and a width of 6mm, and its function is to provide space for adjusting the measuring tube positioning screw;

[0063] The display 4 includes an explosion-proof housing 41, a display screen 42, a parameter display area 43, a power interface 44, and a data cable interface 45; the display power interface 44 is connected to a power source; a switch is provided on the data cable at the data cable interface 45; the data cable can transmit measurement data and power.

[0064] Multiple push rods are connected by threads, and the push rods are connected to the end cap of the diameter measuring device by threads.

[0065] The optocoupler in this embodiment comprises a two-layer structure: an upper layer is a photosensitive unit (pixel unit), and a lower layer is a circuit layer. The circuit layer is connected to the data line and returns the offset x of the imaging point from the front edge of the optocoupler (i.e., the principal optical axis of the receiving lens) to the aperture display. The optocoupler is a rectangular thin sheet with a length, width, and thickness of 20mm, 10mm, and 2mm, respectively.

[0066] In this embodiment, the measuring tube includes an outer measuring tube, an inner measuring tube, positioning screws, and a spiral data cable. The positioning screws are of four sizes: 30mm, 50mm, 100mm, and 200mm, corresponding to measuring ranges of 40–60mm, 40–100mm, 60–200mm, and 120–400mm. The spiral data cable is essentially a part of the data cable and is designed in a spiral shape to facilitate synchronous expansion and contraction with the inner measuring tube.

[0067] Example 2:

[0068] This embodiment provides a method for measuring the aperture of the underground laser aperture measuring device in coal mines, as described in Embodiment 1, including the following steps:

[0069] Before using the device, estimate the size of the hole to be measured, and use a tool to adjust the position of the positioning screw on the measuring tube from the side opening to select the appropriate measuring range.

[0070] Step 1: After passing the push rod through the data cable, fix it to the diameter measuring device. Slowly push it into the hole from the orifice. Connect multiple push rods in sequence until the required hole depth is reached. Record fixed parameters such as the distance between the laser output port and the optical center of the receiving lens, the outer cylinder radius of the diameter measuring device, the angle between the laser and the central axis, and the focal length of the receiving lens.

[0071] Step 2: Connect the power supply, turn on the monitor, close the switch on the data cable, the data cable supplies power to the diameter measuring device inside the hole, the voltage applied to the two ends of the light-emitting diode causes the diode to emit laser light, generating a light source, and the laser emits laser light.

[0072] Step 3: After being focused by a condenser lens, the laser beam enters the borehole in a linear pattern. Diffuse reflection occurs on the borehole wall. The reflection points of the laser beams emitted by the three lasers on the borehole wall are points A, B, and C, respectively. The reflected rays enter the three receiving lenses and are focused, forming images on the three optocouplers, creating a light spot on each optocoupler. Charge accumulates at the location of the light spot, creating a high potential. After digital circuitry calculations, the distance from the light spot position to the front edge of the optocoupler is obtained, i.e., the distance between the light spot and the principal optical axis of the receiving lens. This data is transmitted to the borehole display, where it is processed and the measured borehole diameter is output.

[0073] The borehole diameter measured by the caliper is:

[0074]

[0075] In the above formula, the distances from points A, B, and C to the central axis of the diameter measuring device are a, b, and c, respectively; a = y1 + r, b = y2 + r, c = y3 + r, where y1 is the distance between point A and the outer wall of the diameter measuring device, y2 is the distance between point B and the outer wall of the diameter measuring device, y3 is the distance between point C and the outer wall of the diameter measuring device, and r is the radius of the diameter measuring device.

[0076] like Figure 8 middle, In △ABC, The borehole diameter D was measured.

[0077] The arrangement of the laser, receiving lens, and optocoupler forms a similar triangular relationship. Figure 7 Using the principle of similar triangles, the distance y1 between point A and the outer wall of the caliper can be obtained by solving the following equations simultaneously:

[0078]

[0079] y1=(l-x1 ′ )tanθ

[0080] Where x1 is the distance between the light spot formed by the receiving lens on the optocoupler at point A and the principal optical axis of the receiving lens, in mm; f is the focal length of the receiving lens, in mm; and l is the distance between the laser output port and the optical center of the receiving lens, in mm. ′ Let θ be the distance between point A and the principal optical axis of the receiving lens (in mm), and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

[0081] Similarly, using the principle of similar triangles, the distance y2 between point B and the outer wall of the caliper can be obtained by solving the following equations simultaneously:

[0082]

[0083] y2=(l-x2 ′ )tanθ

[0084] Where x2 is the distance between the light spot formed by the receiving lens on the optocoupler at point B and the principal optical axis of the receiving lens, in mm; f is the focal length of the receiving lens, in mm; and l is the distance between the laser output port and the optical center of the receiving lens, in mm. ′ Let θ be the distance between point B and the principal optical axis of the receiving lens (in mm), and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

[0085] Similarly, using the principle of similar triangles, the distance y3 between point C and the outer wall of the caliper can be obtained by solving the following equations simultaneously:

[0086]

[0087] y3=(l-x3 ′ )tanθ

[0088] Where x3 is the distance between the light spot formed by the receiving lens on the optocoupler at point C and the principal optical axis of the receiving lens, in mm; f is the focal length of the receiving lens, in mm; and l is the distance between the laser output port and the optical center of the receiving lens, in mm. ′ Let C be the distance between point C and the principal optical axis of the receiving lens, in mm, and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

[0089] In this invention, the arrangement of the laser, receiving lens, and optocoupler takes into account the deviation factor of the diameter measuring device. That is, after the diameter measuring device is lowered into the hole, its axis may deviate from the borehole center axis due to its own gravity. In this case, the borehole diameter can be calculated using the principle of three points being concyclic. The calculation principle is as follows: Figure 7 and 8 As shown; when the caliper is deviated from the coaxiality of the borehole, if points A, B and C are not in the same cross-sectional circle, the three points can be projected along the axial direction of the borehole to make them in the same circle and the plane of the circle is perpendicular to the axial direction of the borehole; the distances from points A, B and C to the central axis of the caliper are consistent with the distances from their projection points to the central axis of the caliper.

[0090] In this invention, the push rod can be rotated at a certain angle at the same measuring point to measure several sets of data and take the average value, resulting in a more accurate result. After measuring one set of data, the switch on the data line is turned off, and the push rod is continued to be connected and inserted into the hole until the next measuring point is reached. Steps 1 to 3 are repeated. After all the measuring point hole diameters are measured, the power supply of the display and the data line switch are turned off, the push rod is slowly lifted, and the push rods are removed one by one until the diameter measuring device is lifted away from the hole.

Claims

1. A laser aperture measuring device for underground coal mines, characterized in that, It includes a diameter measuring device (1), a push rod (2), a data cable (3), and a display (4); The diameter measuring device (1) includes an outer cylinder (11), a central shaft (12), a bracket I (13), a laser (14), a receiving lens (15), a bracket II (16), an optocoupler (17), and a measuring tube (18); the central shaft (12) is arranged at the central axis position inside the outer cylinder (11), and one end of the central shaft (12) is fixed to the center of the inner wall of the end cap of the outer cylinder (11); the middle part of the bracket I (13) is fixed on the central shaft (12), and each of the three ends of the bracket I (13) is fixed to the central shaft (12). A laser (14) is connected to the inner wall of the outer cylinder (11), and the three lasers (14) are closely attached to each other and distributed at 120° intervals. A receiving lens (15) is embedded in the side wall of the outer cylinder (11), and the three receiving lenses (15) are distributed at 120° intervals. The principal optical axis of each receiving lens (15) is perpendicular to the central axis of the outer cylinder (11). The middle part of the bracket II (16) is located on the central axis (12), and each of the three ends of the bracket II (16) is connected to an optocoupler (17). The three lasers are connected to the inner wall of the outer cylinder (11) and distributed at 120° intervals. The electrocoupler elements (17) are distributed at 120° to each other; each laser (14) and a receiving lens (15) and an optocoupler element (17) form a diameter measuring unit. In each diameter measuring unit, the line connecting the laser (14) and the receiving lens (15) is parallel to the central axis of the outer cylinder (11). The laser emitted by the laser (14) can pass through the through hole on the outer cylinder (11) and hit the hole wall, and then be reflected to the receiving lens (15). The principal optical axis of the receiving lens (15) is perpendicular to its corresponding optocoupler element (17), and the distance between the optical center of the receiving lens (15) and the optocoupler element (17) is the focal length of the receiving lens (15). The front edge of the optocoupler element (17) is flush with the optical center of the receiving lens (15). The laser transmitted through the receiving lens (15) can be imaged on the optocoupler element (17) and form a light spot. The range tube (18) is sleeved on the central axis (12) and located between the laser (14) and the optocoupler element (17). The end of the push rod (2) is connected to the outer cylinder end cap of the diameter measuring device (1); one end of the data cable (3) passes through the push rod (2) and is connected to the diameter measuring device (1), and the other end is connected to the display (4).

2. The underground laser aperture measuring device for coal mines as described in claim 1, characterized in that, The laser emitted by the laser (14) forms an angle of 45° with the central axis of the outer cylinder (11).

3. The underground laser aperture measuring device for coal mines as described in claim 1, characterized in that, The laser (14) includes a protective cover (141), a light-emitting diode (142), a focusing lens (143), and a light-emitting port (144).

4. The underground laser aperture measuring device for coal mines as described in claim 1, characterized in that, The receiving lens (15) is embedded in the elongated through hole on the side wall of the outer cylinder (11) so that the position of the receiving lens (15) can be adjusted along the axial direction of the outer cylinder (11).

5. The underground laser aperture measuring device for coal mines as described in claim 1, characterized in that, The position of the bracket II (16) on the central axis (12) is adjustable to adjust the axial position of the optocoupler (17).

6. The underground laser aperture measuring device for coal mines as described in claim 1, characterized in that, The outer cylinder (11) has a side opening on its side wall, which is opposite to the measuring tube (18) to adjust the measuring range of the measuring tube (18).

7. A method for measuring the aperture of a laser aperture measuring device for underground coal mines as described in any one of claims 2 to 6, characterized in that, Includes the following steps: Step 1: After passing the push rod through the data cable, fix it to the diameter measuring device. Slowly push it into the hole from the orifice. Connect multiple push rods in sequence until the hole depth to be measured is reached. Record the distance between the laser output port and the optical center of the receiving lens, the outer cylinder radius of the diameter measuring device, the angle between the laser and the central axis, and the focal length of the receiving lens. Step 2: Connect the power supply, turn on the monitor, supply power to the diameter measuring device inside the hole via the data cable, and the laser emits a laser beam; Step 3: The laser beam enters the borehole. The laser beams emitted by the three lasers are reflected at points A, B, and C on the inner wall of the borehole. The reflected light beams enter the three receiving lenses and are focused to form images on the three optocouplers, forming a light spot on each optocoupler. The distance between the light spot and the front edge of the optocoupler is obtained, which is the distance between the light spot and the principal optical axis of the receiving lens. The borehole diameter measured by the caliper is: In the above formula, the distances from points A, B, and C to the central axis of the diameter measuring device are a, b, and c, respectively; a = y1 + r, b = y2 + r, c = y3 + r, where y1 is the distance between point A and the outer wall of the diameter measuring device, y2 is the distance between point B and the outer wall of the diameter measuring device, y3 is the distance between point C and the outer wall of the diameter measuring device, and r is the radius of the diameter measuring device.

8. The method for measuring the aperture of the underground laser aperture measuring device in coal mines as described in claim 7, characterized in that, The distance y1 between point A and the outer wall of the caliper is obtained by solving the following equations simultaneously: y1=(l-x1 ′ )tanθ Where x1 is the distance between the light spot formed by the receiving lens on the optocoupler at point A and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, and l is the distance between the laser output port and the optical center of the receiving lens. ′ Let θ be the distance between point A and the principal optical axis of the receiving lens, and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

9. The method for measuring the aperture of the underground laser aperture measuring device in coal mines as described in claim 7, characterized in that, The distance y2 between point B and the outer wall of the caliper is obtained by solving the following equations simultaneously: y2=(l-x2 ′ tanθ Where x2 is the distance between the light spot formed by the receiving lens on the optocoupler at point B and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, and l is the distance between the laser output port and the optical center of the receiving lens. ′ Let θ be the distance between point B and the principal optical axis of the receiving lens, and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

10. The method for measuring the aperture of the underground laser aperture measuring device in coal mines as described in claim 7, characterized in that, The distance y3 between point C and the outer wall of the caliper is obtained by solving the following equations simultaneously: y3=(l-x3 ′ tanθ Where x3 is the distance between the light spot formed by the receiving lens on the optocoupler at point C and the principal optical axis of the receiving lens, f is the focal length of the receiving lens, and l is the distance between the laser output port and the optical center of the receiving lens. ′ Let C be the distance between point C and the principal optical axis of the receiving lens, and θ be the angle between the laser and the central axis of the diameter measuring device; by combining the above two equations, we obtain...

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