A borehole camera probe error correction method, device and system

Abstract

The application provides a borehole camera probe error correction method, device and system, and relates to the technical field of geological exploration.The borehole camera probe error correction method comprises the following steps: a borehole camera gray scale feature model is established; a borehole wall development drawing is acquired; three-dimensional coordinates of a borehole camera probe are determined according to the image gray scale features of the borehole wall development drawing and the borehole camera gray scale feature model; eccentric gray scale error and eccentric perspective error are determined according to the three-dimensional coordinates and the borehole camera gray scale feature model; and error correction is performed on the borehole wall development drawing according to the eccentric gray scale error and the eccentric perspective error.The technical scheme can correct the gray scale error and the perspective error caused by probe eccentricity during the operation of the borehole camera system, thereby improving the measurement accuracy of the borehole camera system.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, and more specifically, to a method, apparatus, and system for correcting errors in borehole camera probes. Background Technology

[0002] Borehole imaging technology is a technique that utilizes optical principles and related equipment to acquire images of the borehole wall. By employing borehole imaging technology, engineering geological information within the borehole can be obtained accurately and quickly. Borehole imaging equipment typically consists of components such as a borehole camera probe and a controller. The borehole camera probe includes components such as a light source and a camera. When the borehole imaging equipment is operating, the light source illuminates the borehole wall, and the camera captures the image of the borehole wall.

[0003] The existing drilling camera technology has the following problems: (1) When the existing drilling camera equipment is working, it cannot guarantee that the drilling camera probe is on the drilling axis, that is, there is a situation of probe eccentricity, which makes it impossible for the existing drilling camera technology to achieve three-dimensional positioning of the drilling camera probe in the hole; (2) The eccentricity of the drilling camera probe will cause grayscale error and perspective error in the drilling image. The existing drilling camera technology cannot compensate for such errors. Summary of the Invention

[0004] The problem solved by this invention is how to achieve error correction of a borehole camera probe.

[0005] To address the above problems, this invention provides a method for correcting errors in a borehole camera probe, comprising:

[0006] Establish a grayscale feature model of borehole camera footage;

[0007] Obtain a borehole wall unfolded image, and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model;

[0008] The eccentric grayscale error and eccentric perspective error are determined based on the three-dimensional coordinates and the borehole camera grayscale feature model.

[0009] The borehole wall unfolding diagram is corrected based on the eccentric grayscale error and the eccentric perspective error.

[0010] Optionally, the borehole camera grayscale feature model is represented as:

[0011]

[0012] Where D(θ, h) represents the grayscale value of point (θ, h) on the developed borehole wall diagram, λ represents the grayscale parameter, S represents the geometric path from point (θ, h) to the light source, and r B This indicates the radius of the borehole wall.

[0013] Optionally, the grayscale parameter is related to device parameters, scan line radius, and aperture wall reflectivity.

[0014] Optionally, establishing the borehole camera grayscale feature model includes:

[0015] The exposure at any point is determined based on optical principles;

[0016] The grayscale value of the corresponding pixel is determined based on the exposure amount and the photosensitive coefficient of the camera.

[0017] Optionally, determining the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded diagram and the borehole camera grayscale feature model includes: using the least squares method to fit and determine the three-dimensional coordinates of the borehole camera probe.

[0018] Optionally, the eccentric grayscale error is expressed as:

[0019]

[0020] Where B(θ, h) represents the eccentric grayscale error, S represents the geometric path from point (θ, h) to the light source, and r B This indicates the radius of the borehole wall.

[0021] Optionally, the step of correcting the borehole wall unfolded image based on the eccentric grayscale error and the eccentric perspective error includes:

[0022] The developed image of the borehole wall after grayscale correction is determined based on the eccentric grayscale error.

[0023] The developed image of the borehole wall after perspective correction is determined based on the eccentric perspective error.

[0024] The borehole camera probe error correction method of the present invention determines the three-dimensional coordinates of the borehole camera probe based on the established borehole camera grayscale feature model and the image grayscale features of the borehole wall unfolded diagram. Based on the image grayscale features, the borehole camera probe is three-dimensionally positioned in the borehole. Then, based on the three-dimensional position of the probe in the borehole, the eccentric grayscale error and eccentric perspective error are determined. The method corrects the grayscale error and perspective error caused by probe eccentricity during the operation of the borehole camera system, thereby improving the measurement accuracy of the borehole camera system.

[0025] The present invention also provides a drilling camera probe error correction device, comprising:

[0026] Modeling unit, used to establish grayscale feature model of borehole camera footage;

[0027] The coordinate unit is used to obtain the borehole wall unfolded image and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model.

[0028] An error unit is used to determine the eccentric grayscale error and eccentric perspective error based on the three-dimensional coordinates and the borehole camera grayscale feature model.

[0029] The correction unit is used to correct the error of the borehole wall unfolded diagram based on the eccentric grayscale error and the eccentric perspective error.

[0030] The drilling camera probe error correction device and the drilling camera probe error correction method described above have the same advantages over the prior art, and will not be repeated here.

[0031] This invention also provides a borehole camera probe error correction system, including a computer-readable storage medium storing a computer program and a processor. The computer program is read and executed by the processor to implement the above-described borehole camera probe error correction method. The advantages of this borehole camera probe error correction system over the prior art are the same as those of the above-described borehole camera probe error correction method, and will not be repeated here.

[0032] The present invention also provides a computer-readable storage medium storing a computer program, which, when read and executed by a processor, implements the above-described drilling camera probe error correction method. The advantages of the computer-readable storage medium and the above-described drilling camera probe error correction method compared to the prior art are the same and will not be repeated here. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the borehole camera probe error correction method according to an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the optical principle of grayscale features in borehole imaging according to an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram of the borehole wall coordinate system and probe coordinate system according to an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1-Drill hole wall; 2-Drilling camera probe; 3-CMOS camera; 4-LED dot matrix light source; 5-Frusted conical reflector. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] like Figure 1 As shown, an embodiment of the present invention provides a method for correcting errors in a borehole camera probe, comprising:

[0040] Establish a grayscale feature model of borehole camera footage;

[0041] Obtain a borehole wall unfolded image, and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model;

[0042] The eccentric grayscale error and eccentric perspective error are determined based on the three-dimensional coordinates and the borehole camera grayscale feature model.

[0043] The borehole wall unfolding diagram is corrected based on the eccentric grayscale error and the eccentric perspective error.

[0044] Specifically, the error correction methods for borehole camera probes include:

[0045] I. Establishing a grayscale feature model for borehole camera footage: combining Figure 2 As shown, when the borehole camera system is working, according to optical principles, the position of the borehole camera probe 2 within the hole is represented by a series of grayscale features in the borehole image at the corresponding depth. When the borehole camera probe is working in the borehole, the LED dot matrix light source 4 illuminates the borehole wall 1 through reflection from the conical reflector. The CMOS camera 3 captures a panoramic image of the borehole wall through reflection from the truncated conical reflector 5.

[0046] According to the principles of optical imaging, for a point on the inner wall of a drill hole captured by a CMOS camera, the geometrical distance S of the light source illuminating that point can be expressed as:

[0047] S = h s +ρcos(t)csc(t+2ψ)+h l

[0048]

[0049] h l =(r-r0)tan(ψ)

[0050] Where ρ is the horizontal distance between the probe center and a point on the borehole wall; r is the scan line radius; h l The distance between the scan line and the apex of the truncated conical mirror is t; t is a parameter; r0 is the radius of the truncated conical mirror apex; h s h is the distance between the light source inside the probe and the end face of the truncated conical mirror. c Let h be the distance between the optical center of the CMOS camera and the upper surface of the truncated conical mirror. For drilling camera equipment, h is... s =h c ψ is the base angle of the truncated conical mirror.

[0051] According to geometric principles, the angle between the ray of light from the probe light source illuminating the borehole wall and the normal to the borehole wall is... Represented as:

[0052]

[0053] Combination Figure 3 As shown, the borehole axis O at depth h = 0 B Establish a cylindrical coordinate system with the pole at north, the polar axis at due north, and the borehole axis at the z-axis.

[0054] Then the probe center O P The cylindrical coordinates are (k(h)·r) B ,θ0,h), where, r B D is the radius of the borehole wall. BP (h) is the borehole wall axis O B With probe axis O P The distance between the polar axis and O, θ0 is the distance between the polar axis and O. B O P The included angle.

[0055] Combination Figure 3 As shown, with the probe axis O P Let be the pole, north be the polar axis, and the borehole axis be the z-axis, establishing a cylindrical coordinate system. The horizontal distance between the probe center and a point on the borehole wall can then be calculated using the following formula:

[0056]

[0057] Where θ is the polar angle of a point on the borehole wall in the probe coordinate system.

[0058] Illuminance, also known as light intensity, refers to the luminous flux received per unit area. According to the law of illuminance, the illuminance E of an object illuminated by a point light source can be calculated using the following formula:

[0059]

[0060] Where I is the luminous intensity of the light source.

[0061] The luminance of a non-luminous object refers to the luminous flux reflected per unit area from the surface of the object. The luminance B at a point on the wall of the aperture can be calculated by the following formula:

[0062] B = K·E (5)

[0063] Where K is the surface reflectivity of the hole wall.

[0064] In the CMOS camera imaging process, the relationship between the grayscale value of each pixel in the image and the exposure of the object at the corresponding location can be expressed as:

[0065] D(i,j)=γlgH(i,j)+m (6)

[0066] Where D(i,j) is the gray value of a point on the image, H(i,j) is the exposure corresponding to that point, and γ and m are the photosensitive characteristic parameters of the CMOS sensor.

[0067] The exposure H and the image plane illuminance are related as follows:

[0068] H = E0·T (7)

[0069] Where E0 is the image illuminance and T is the exposure time.

[0070] According to optical principles, the relationship between image plane illuminance and borehole wall brightness in a borehole camera system can be expressed as:

[0071]

[0072] Where τ is the lens's transmission coefficient, f is the lens's focal length, and d is the lens's diameter.

[0073] From equations (4) to (8), for a uniform borehole wall, the grayscale value D(θ,h) of a point on the unfolded diagram can be calculated by the following formula:

[0074]

[0075]

[0076] The value of the grayscale parameter λ is related to the equipment parameters, scan line radius, and aperture wall reflectivity. For given equipment parameters, scan line parameters, and uniform aperture walls, λ is a constant. For drilling camera equipment, the contrast coefficient γ of a CMOS camera is 1.

[0077] With the borehole axis O at a depth h = 0 B Let be the pole, north be the polar axis, and the borehole axis be the z-axis; establish a cylindrical coordinate system. Then, when the borehole camera probe position is (kr... B When θ = 0, h), for a point (θ, h) on the developed diagram of the hole wall, we have:

[0078]

[0079] Equation (10) is the grayscale feature model of the three-dimensional position image of the borehole camera probe.

[0080] 2. Obtain the unfolded image of the borehole wall, and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the unfolded borehole wall and the borehole camera grayscale feature model.

[0081] ① Read the developed diagram of the borehole wall.

[0082] ② For the grayscale value D(i,h) of any row E(i,h) on the borehole wall unfolding diagram, use the least squares estimation method to obtain the estimates of the parameters λ, k(h), and θ0(h) in the formula. The calculation is as follows:

[0083]

[0084] in, Take parameters The calculated value of formula (10) is given.

[0085] ③ For a borehole wall development diagram E(i,j), the borehole camera parameters and scan line radius are the same. For borehole wall sections with similar lithology, the surface reflectivity K can be treated as a constant. Therefore, for the borehole wall development diagram E(i,j), the estimate of parameter λ is... It can be represented as:

[0086]

[0087] ④ After fixing the estimate of parameter λ, use the least squares estimation method again to obtain the estimates of parameters k(h) and θ0(h) in equation (10). The calculation is as follows:

[0088]

[0089] in, Take parameters The calculated value of formula (10) is given.

[0090] The estimated three-dimensional coordinates of the probe are obtained by solving for them, denoted as .

[0091] 3. Determine the eccentric grayscale error and eccentric perspective error based on the three-dimensional coordinates and the borehole camera grayscale feature model.

[0092] When generating the developed borehole wall diagram, the drilling camera system calculates the diagram with the probe axis as the center. Since the probe's position within the borehole is not fixed in the center, this method results in grayscale errors in the generated developed borehole wall diagram.

[0093] For any point (θ, h) on the developed diagram of the borehole wall, according to equation (10), when the borehole camera probe is centered in the borehole, we have:

[0094]

[0095] The grayscale value of that point is:

[0096] D0(θ,h)=lgλ (15)

[0097] Where D0 is the gray value of a point on the hole wall when the probe is centered.

[0098] Based on the working principle of the borehole camera system, when the position of the borehole camera probe is (kr) B When θ0,h), the grayscale error image B(θ,h) caused by probe misalignment can be expressed as:

[0099] B(θ,h)=D(θ,h)-D0(θ,h) (16)

[0100] From equations (10), (15), and (16), we get:

[0101]

[0102] The grayscale error image of the borehole wall unfolded can be calculated using equation (17). As shown in equation (16), the grayscale-corrected borehole wall unfolded image can be obtained by performing image grayscale subtraction between the original borehole wall unfolded image D(θ,h) and the calculated error image B(θ,h).

[0103] Fourth, the borehole wall unfolding diagram is corrected based on the eccentric grayscale error and the eccentric perspective error.

[0104] When generating the borehole wall unfolding diagram, the drilling camera system unfolds the diagram with the probe axis as the center. Therefore, when the probe is not centered in the borehole, the polar angle θ of a point on the borehole wall in the probe coordinate system will be different. P θ with the borehole coordinate system B There are errors between them.

[0105] For any depth h, θ at any point on the hole wall P With θ B There is a mathematical relationship between them, which can be expressed as:

[0106]

[0107] According to equation (18), the developed diagram of the borehole wall after perspective correction, E'(θ), can be constructed. B ,h), is represented as:

[0108] E'(θ B ,h)=E(θ P ,h) (19)

[0109] The developed image of the borehole wall after perspective correction can be calculated using equation (19).

[0110] Optionally, the borehole camera grayscale feature model is represented as:

[0111]

[0112] Where D(θ, h) represents the grayscale value of point (θ, h) on the developed borehole wall diagram, λ represents the grayscale parameter, S represents the geometric path from point (θ, h) to the light source, and r B This indicates the radius of the borehole wall.

[0113] Optionally, the grayscale parameter is related to device parameters, scan line radius, and aperture wall reflectivity.

[0114] Optionally, establishing the borehole camera grayscale feature model includes:

[0115] The exposure at any point is determined based on optical principles;

[0116] The grayscale value of the corresponding pixel is determined based on the exposure amount and the photosensitive coefficient of the camera.

[0117] Optionally, determining the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded diagram and the borehole camera grayscale feature model includes: using the least squares method to fit and determine the three-dimensional coordinates of the borehole camera probe.

[0118] Optionally, the eccentric grayscale error is expressed as:

[0119]

[0120] Where B(θ, h) represents the eccentric grayscale error, S represents the geometric path from point (θ, h) to the light source, and r B This indicates the radius of the borehole wall.

[0121] Optionally, the step of correcting the borehole wall unfolded image based on the eccentric grayscale error and the eccentric perspective error includes:

[0122] The developed image of the borehole wall after grayscale correction is determined based on the eccentric grayscale error.

[0123] The developed image of the borehole wall after perspective correction is determined based on the eccentric perspective error.

[0124] Another embodiment of the present invention provides a borehole camera probe error correction device, comprising:

[0125] Modeling unit, used to establish grayscale feature model of borehole camera footage;

[0126] The coordinate unit is used to obtain the borehole wall unfolded image and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model.

[0127] An error unit is used to determine the eccentric grayscale error and eccentric perspective error based on the three-dimensional coordinates and the borehole camera grayscale feature model.

[0128] The correction unit is used to correct the error of the borehole wall unfolded diagram based on the eccentric grayscale error and the eccentric perspective error.

[0129] Another embodiment of the present invention provides a borehole camera probe error correction system, including a computer-readable storage medium storing a computer program and a processor, wherein the computer program is read and executed by the processor to implement the above-mentioned borehole camera probe error correction method.

[0130] Another embodiment of the present invention provides a computer-readable storage medium storing a computer program, which is read and executed by a processor to implement the above-mentioned drilling camera probe error correction method.

[0131] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for correcting errors in a borehole camera probe, characterized in that, include: Establish a grayscale feature model of borehole camera footage; Obtain a borehole wall unfolded image, and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model; The eccentric grayscale error and eccentric perspective error are determined based on the three-dimensional coordinates and the borehole camera grayscale feature model. The borehole wall unfolding diagram is corrected based on the eccentric grayscale error and the eccentric perspective error. The borehole camera grayscale feature model is represented as follows: ； Where D(θ, h) represents the grayscale value of point (θ, h) on the developed diagram of the borehole wall, λ represents the grayscale parameter, S represents the geometric path from point (θ, h) to the light source, and r B Indicates the radius of the borehole wall; The eccentric grayscale error is expressed as: ； Where B(θ, h) represents the eccentric grayscale error, S represents the geometric path from point (θ, h) to the light source, and r B Indicates the radius of the borehole wall; The step of correcting the borehole wall unfolded diagram based on the eccentric grayscale error and the eccentric perspective error includes: The developed image of the borehole wall after grayscale correction is determined based on the eccentric grayscale error. The developed image of the borehole wall after perspective correction is determined based on the eccentric perspective error.

2. The drilling camera probe error correction method according to claim 1, characterized in that, The grayscale parameters are related to the device parameters, scan line radius, and aperture wall reflectivity.

3. The drilling camera probe error correction method according to claim 1, characterized in that, The establishment of the borehole camera grayscale feature model includes: The exposure at any point is determined based on optical principles; The grayscale value of the corresponding pixel is determined based on the exposure amount and the photosensitive coefficient of the camera.

4. The drilling camera probe error correction method according to claim 1, characterized in that, The step of determining the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolding diagram and the borehole camera grayscale feature model includes: using the least squares method to fit and determine the three-dimensional coordinates of the borehole camera probe.

5. A drilling camera probe error correction device, characterized in that, include: Modeling unit, used to establish grayscale feature model of borehole camera footage; The coordinate unit is used to obtain the borehole wall unfolded image and determine the three-dimensional coordinates of the borehole camera probe based on the image grayscale features of the borehole wall unfolded image and the borehole camera grayscale feature model. An error unit is used to determine the eccentric grayscale error and eccentric perspective error based on the three-dimensional coordinates and the borehole camera grayscale feature model. The correction unit is used to correct the error of the borehole wall unfolded diagram based on the eccentric grayscale error and the eccentric perspective error. The borehole camera grayscale feature model is represented as follows: ； Where D(θ, h) represents the grayscale value of point (θ, h) on the developed diagram of the borehole wall, λ represents the grayscale parameter, S represents the geometric path from point (θ, h) to the light source, and r B Indicates the radius of the borehole wall; The eccentric grayscale error is expressed as: ； Where B(θ, h) represents the eccentric grayscale error, S represents the geometric path from point (θ, h) to the light source, and r B Indicates the radius of the borehole wall; The step of correcting the borehole wall unfolded diagram based on the eccentric grayscale error and the eccentric perspective error includes: The developed image of the borehole wall after grayscale correction is determined based on the eccentric grayscale error. The developed image of the borehole wall after perspective correction is determined based on the eccentric perspective error.

6. A borehole camera probe error correction system, characterized in that, The method includes a computer-readable storage medium storing a computer program and a processor, the computer program being read and executed by the processor to implement the borehole camera probe error correction method as described in any one of claims 1 to 4.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which is read and executed by a processor to implement the drilling camera probe error correction method as described in any one of claims 1 to 4.

Images