CN-116784778-B - Real-time correction method and device for endoscope image distortion

Abstract

The invention provides a real-time correction method for endoscope image distortion, which comprises the steps of placing an improved hard tube endoscope system at a target position, setting working conditions, firstly carrying out laser gating projection correction in each frame of an image of a biological tissue part collected by an endoscope, carrying out homogeneous transformation matrix calculation on a projection distortion correction line image and a correction line reference image, then obtaining a current endoscope distortion image collected by a CCD camera again, carrying out operation processing by adopting the homogeneous transformation matrix, obtaining an endoscope correction image, and displaying the corrected image for human eyes to observe through a display, namely, obtaining the image without distortion. Because the reference image period of the pulse laser projection correction line is extremely short and is far smaller than the human eye vision persistence period, an observer cannot perceive the laser gating projection correction process, the dynamic property and the real-time property of image correction are ensured, biological tissues cannot be damaged by weak laser instantaneous exposure, and the medical safety of image correction is ensured.

Inventors

• XUE WEI
• CAO YU
• LIU WENWEN
• CHEN JIE
• HOU ZHISHAN
• ZHAO FANG
• WEI XINLEI

Assignees

• 瓯江实验室

Dates

Publication Date

20260505

Application Date

20230619

Claims (4)

1. 1. A method for correcting distortion of an endoscope image in real time, comprising the steps of: placing the improved rigid tube endoscope system at a target position and setting working conditions; The improved hard tube endoscope system comprises an endoscope tube (1), an outer endoscope tube (2), a laser gating projection correction device, an optical imaging system and an illumination optical fiber (3); the endoscope tube (1) and the outer endoscope tube (2) are hollow tubes, the endoscope tube (1) is arranged in an inner cavity of the outer endoscope tube (2), and a gap is reserved between the endoscope tube (1) and the outer endoscope tube (2) along the radial direction; The optical imaging system comprises a display screen, an image processing unit, a CCD (charge coupled device) camera (4), a cylindrical lens group (7) and an objective lens (6), wherein the cylindrical lens group (7) and the objective lens (6) are arranged in an inner cavity of the inner lens tube (1), the objective lens (6) is positioned at one end part of the inner lens tube (1), the other end part of the inner lens tube (1) is connected with the CCD camera (4), objective lens glass is arranged outside the objective lens (6), the cavity of the inner lens tube (1) is sealed by tightly welding or firmly adhering the objective lens glass and the inner lens tube (1), an image acquired by the objective lens (6) is imaged by the CCD camera (4) after being transmitted by the cylindrical lens group (7), and the CCD camera (4) is connected with the image processing unit and displays the processed image through the display screen; The illumination optical fiber (3) is arranged in a gap between the inner lens tube (1) and the outer lens tube (2), and the gap is sealed at the objective lens end through light-transmitting glass, the side wall of the outer lens tube (2) is provided with a light cone (5) for being connected with the illumination optical fiber (3), one end of the illumination optical fiber (3) is connected with the light cone (5) arranged on the side wall of the outer lens tube (2), the other end of the illumination optical fiber is connected to the objective lens end, and light is emitted out of the endoscope from the objective lens end to illuminate the body; The laser gating projection correction device comprises a pulse laser, a beam shaper, a semi-transparent and semi-reflective mirror (8) and a synchronous controller, wherein the synchronous controller is connected with a CCD camera (4) and the pulse laser through control lines and is used for synchronizing the working cycles of the pulse laser and the semi-transparent and semi-reflective mirror; The semi-transparent and semi-reflective mirror (8) is fixedly arranged in a gap between the CCD camera (4) of the endoscope tube (1) and the cylindrical lens group (7), laser input holes for being connected with pulse laser beams are formed in the endoscope tube (1) and the outer endoscope tube (2), the semi-transparent and semi-reflective mirror (8) is opposite to the two laser input holes, incident light in the horizontal direction can be reflected into vertical coaxial light, and the vertical incident light is transmitted; the horizontal laser beam emitted by the pulse laser is shaped into a geometric linear beam through a beam shaper, the geometric linear beam is called a corrected line reference image, the geometric linear beam horizontally enters the half mirror (8) through a laser incidence hole, vertically enters the transparent glass at the end of the objective lens after being reflected by the half mirror (8), passes through the transparent glass to irradiate the surface of a target biological tissue, and presents a linear light pattern on the surface of the target biological tissue, which is called a projection distortion corrected line image; In each frame of the biological tissue part image acquired by the endoscope, firstly, performing laser gating projection correction, wherein the period is less than 10ms, namely, a synchronous controller of a laser gating projection correction device sends a synchronous starting signal once, so that a pulse laser projects a correction line reference image, meanwhile, a CCD camera (4) acquires a projection distortion correction line image, the projection distortion correction line image and the correction line reference image are subjected to homogeneous transformation matrix calculation, then, the current endoscope distortion image acquired by the CCD camera (4) is acquired again, the previous acquired homogeneous transformation matrix is adopted for operation processing, an endoscope correction image is obtained, and the corrected image is displayed by a display for human eyes to observe, so that the image without distortion is obtained.
2. 2. The method for correcting the distortion of the endoscope image according to claim 1, wherein the laser beam emitted by the pulse laser is required to have no damage to the surface of the biological tissue of the human body, the power is less than 50mW, the pulse width is less than 10ms, and the laser color adopts a visible light wave band.
3. 3. The method for real-time correction of image distortion of an endoscope according to claim 1, wherein the horizontal laser beam emitted from the pulse laser is shaped into a field-shaped beam by a beam shaper.
4. 4. An improved hard tube endoscope system is characterized by comprising an endoscope tube (1), an outer endoscope tube (2), a laser gating projection correction device, an optical imaging system and an illumination optical fiber (3); the endoscope tube (1) and the outer endoscope tube (2) are hollow tubes, the endoscope tube (1) is arranged in an inner cavity of the outer endoscope tube (2), and a gap is reserved between the endoscope tube (1) and the outer endoscope tube (2) along the radial direction; The optical imaging system comprises a display screen, an image processing unit, a CCD (charge coupled device) camera (4), a cylindrical lens group (7) and an objective lens (6), wherein the cylindrical lens group (7) and the objective lens (6) are arranged in an inner cavity of the inner lens tube (1), the objective lens (6) is positioned at one end part of the inner lens tube (1), the other end part of the inner lens tube (1) is connected with the CCD camera (4), objective lens glass is arranged outside the objective lens (6), the cavity of the inner lens tube (1) is sealed by tightly welding or firmly adhering the objective lens glass and the inner lens tube (1), an image acquired by the objective lens (6) is imaged by the CCD camera (4) after being transmitted by the cylindrical lens group (7), and the CCD camera (4) is connected with the image processing unit and displays the processed image through the display screen; The illumination optical fiber (3) is arranged in a gap between the inner lens tube (1) and the outer lens tube (2), and the gap is sealed at the objective lens end through light-transmitting glass, the side wall of the outer lens tube (2) is provided with a light cone (5) for being connected with the illumination optical fiber (3), one end of the illumination optical fiber (3) is connected with the light cone (5) arranged on the side wall of the outer lens tube (2), the other end of the illumination optical fiber is connected to the objective lens end, and light is emitted out of the endoscope from the objective lens end to illuminate the body; The laser gating projection correction device comprises a pulse laser, a beam shaper, a semi-transparent semi-reflecting mirror (8) and a synchronous controller, wherein the synchronous controller is connected with a CCD camera (4) and the pulse laser through control lines and used for synchronizing working cycles of the two semi-transparent semi-reflecting mirror (8), the semi-transparent semi-reflecting mirror (8) is fixedly arranged in a gap between the CCD camera (4) of an endoscope tube (1) and a cylindrical lens group (7), laser input holes for being connected with pulse laser beams are formed in the endoscope tube (1) and an external endoscope tube (2), the semi-transparent semi-reflecting mirror (8) is opposite to the two laser input holes, incident light in the horizontal direction can be reflected into vertical coaxial light, and incident light in the vertical direction is transmitted.

Description

Real-time correction method and device for endoscope image distortion Technical Field The invention belongs to the field of medical equipment, and particularly relates to a real-time correction method for endoscope image distortion. Background An endoscope is a commonly used medical instrument, which is guided into a pre-inspected organ through a natural duct of a human body or a small incision caused by minimally invasive surgery to realize disease diagnosis. Endoscopes are necessary tools for fine examination of the interior and the surgery and minimally invasive surgery treatment, and the diagnosis and treatment superiority of the endoscopes reach common consensus in the medical community. The medical hard tube endoscope is an endoscope with an inflexible insertion part in operation and is widely applied to examination and minimally invasive treatment of ear, nose and throat, abdominal cavity, uterine cavity, thoracic cavity, joints and urinary tract. In order to improve the observation range of the endoscope, a larger field of view (generally 120 °) is required, the diameter of the endoscope head is limited by the body cavity of the human body, the external dimension of the imaging system cannot be large, and the imaging optical system cannot be complex, so that the optical imaging system of the endoscope generally has serious optical distortion, which affects the doctor to correctly judge the lesion. The distortion of the lens is mainly divided into radial distortion and tangential distortion. Radial distortion is a distortion distributed along the radius direction of the lens, and is generated because light rays are bent more at the center of the principle lens than at the position close to the center, and the distortion is more obvious in a common cheap lens, and the radial distortion mainly comprises barrel-shaped distortion and pincushion-shaped distortion. Tangential distortion is caused by the lens itself being non-parallel to the camera sensor plane or image plane, which is often caused by mounting deviations from the lens being affixed to the lens module. In addition, for the medical hard tube endoscope, the observed surface structure of the biological tissue in the human body is complex, the surface structure cannot be always parallel to the lens, the space position between the surface structure and the lens is changed in real time, and the three-dimensional imaging profile image distortion of the biological tissue, which is changed in real time, can be generated. Therefore, the image distortion of the endoscope system is corrected, the distortion of the image can be effectively improved, the lesion part can be accurately reflected, and the method has important significance for rapidly and accurately positioning the focus. However, the conventional distortion correction method at present cannot achieve real-time, dynamic and accurate distortion correction. Disclosure of Invention The invention provides a real-time correction method for endoscope image distortion, which aims at the defects of the prior art. The real-time correction method for the endoscope image distortion can correct the endoscope image distortion in real time, dynamically and accurately, and effectively improve the distortion of the image. The invention is realized by the following technical scheme: a real-time correction method for endoscope image distortion comprises the following steps: (1) Placing the improved rigid tube endoscope system at a target position and setting working conditions; The improved hard tube endoscope system comprises an endoscope tube, an outer endoscope tube, a laser gating projection correction device, an optical imaging system and an illumination optical fiber; the inner lens tube and the outer lens tube are hollow tubes, the inner lens tube is arranged in an inner cavity of the outer lens tube, and a gap is reserved between the inner lens tube and the outer lens tube along the radial direction; The optical imaging system comprises a display screen, an image processing unit, a CCD camera, a cylindrical lens group and an objective lens, wherein the cylindrical lens group and the objective lens are arranged in an inner cavity of the endoscope tube, the objective lens is positioned at one end part of the endoscope tube, and the other end part of the endoscope tube is connected with the CCD camera; The device comprises an inner lens, an outer lens, an illumination optical fiber, a light cone, a lens cover and a lens cover, wherein the illumination optical fiber is arranged in a gap between the inner lens and the outer lens, and the gap is sealed at the end of the lens through light-transmitting glass; The laser gating projection correction device comprises a pulse laser, a beam shaper, a half-mirror and a synchronous controller, wherein the synchronous controller is connected with a CCD camera and the pulse laser through control lines and is used for synchronizing the working cycles of the CCD camera