Ophthalmic multi-modal imaging combined calibration device and calibration method

Abstract

The application relates to an ophthalmic multimodal imaging joint calibration device and a calibration method. The device comprises a variable diaphragm, an eye simulation lens, a water room and a calibration plate. The eye simulation lens is placed at the best working distance of the calibrated equipment. The variable diaphragm is placed in front of the front surface of the eye simulation lens, and the light aperture of the variable diaphragm can be adjusted at will. The calibration plate is placed at the back focal plane of the eye simulation lens, and a calibration pattern is drawn on the front surface of the calibration plate. The front surface of the calibration plate, the rear surface of the eye simulation lens and the water room form a closed space, and the inside can be injected with liquid. The application is mainly used for joint imaging calibration of fundus camera equipment and ophthalmic OCT equipment, and solves the problem of poor spatial matching of imaging data when two modal instruments are used for joint imaging.

Description

Technical Field

[0001] This invention belongs to the field of ophthalmic optical imaging and relates to an ophthalmic multimodal imaging joint calibration device and calibration method, particularly to the joint imaging calibration of fundus camera equipment and ophthalmic OCT equipment. Background Technology

[0002] The human eye has a complex physiological structure, and examination of the retina can accurately diagnose a variety of eye diseases and systemic diseases. Currently, commonly used fundus imaging techniques in clinical practice mainly include ophthalmoscopy, fundus cameras, laser scanning ophthalmoscopy, and optical coherence tomography (OCT). However, in actual clinical diagnosis and treatment, relying solely on imaging data from a single modality has significant limitations and cannot meet the needs of precision medicine. Therefore, doctors usually need to combine multiple imaging data for joint analysis to improve the accuracy and comprehensiveness of diagnosis. Among these, the combined application of fundus cameras and ophthalmic OCT has played a crucial role in the early diagnosis and disease monitoring of diseases such as diabetic retinopathy, glaucoma, macular degeneration, and retinal vein occlusion. It not only effectively reduces the risk of missed diagnoses and misdiagnoses but also provides more comprehensive and accurate information for assessing fundus diseases.

[0003] However, the combined examination of fundus cameras and ophthalmic OCT faces a key problem: poor spatial matching of imaging data. Since fundus cameras and ophthalmic OCT are two relatively independent optical imaging systems, installation errors and mechanical structural deviations can lead to inconsistencies in imaging positions. This results in spatial transformation differences such as displacement, rotation, and scaling between the two modalities of imaging data, and their fields of view also differ significantly. These issues make direct comparison or integrated analysis of the two modalities difficult during diagnosis, increasing the likelihood of misdiagnosis and missed diagnosis, and posing significant technical challenges to retinal 3D reconstruction and subsequent medical image processing. Furthermore, existing calibration devices require manual calculation of the maximum imaging field of view based on the half-field angle, a time-consuming and labor-intensive calibration process. Summary of the Invention

[0004] The purpose of this invention is to provide a joint calibration device and method for ophthalmic multimodal imaging, which can realize the joint imaging calibration of fundus camera equipment and ophthalmic OCT equipment, and solve the problem of poor spatial matching of imaging data when the two types of instruments are used for joint imaging.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] The ophthalmic multimodal imaging joint calibration device includes a variable aperture, an eye-like lens, a water chamber, and a calibration plate.

[0007] Furthermore, the variable aperture, the simulated eye lens, the water chamber, and the calibration plate are placed coaxially in sequence. The variable aperture is placed on the front surface of the simulated eye lens, which is positioned at the optimal working distance of the device being calibrated. The calibration plate is placed at the back focal plane of the simulated eye lens, and the water chamber is located in the area between the front surface of the calibration plate and the back surface of the simulated eye lens. The water chamber is a hollow cylinder, and the front surface of the calibration plate, the back surface of the simulated eye lens, and the water chamber together form a sealed space, which can be injected with liquid.

[0008] Furthermore, the variable aperture simulates the human eye pupil and is mainly used to control the amount of light transmitted, with its aperture diameter adjustable from 2mm to 8mm.

[0009] Furthermore, the eye-like lens simulates the cornea and lens of the human eye, with a back focal length of 16.6 mm; the eye-like lens is an optical glass lens with a working wavelength of 400 nm to 1200 nm.

[0010] Furthermore, the water chamber simulates the water chamber of the human eye, and its shape is a hollow cylinder. The front surface of the calibration plate, the rear surface of the simulated eye lens, and the water chamber together form a sealed space, which can be injected with pure water or physiological saline.

[0011] Furthermore, the calibration plate simulates the human retina. The calibration plate is a circular transparent glass plate with a diameter greater than 20mm. The front surface of the calibration plate is decorated with a central optical axis point, spatial calibration pattern, field of view scale, and quadrant symbols. All graphics on the front surface of the calibration plate are drawn with a low-reflection material and are painted in black.

[0012] Furthermore, the field of view scale is a four-segment scale of equal length with the central optical axis as the center of symmetry. The scale has 51 graduation lines, each representing 1 degree, and the field of view measurement range is 10° to 60°. The graduation lines of the scale are drawn according to the formula Y = f × tan w, where Y is the half field of view height, f is the effective focal length, and w is the half field of view angle. The effective focal length f = 16.6 mm. The graduation lines of the scale are denser near the central optical axis and sparser further away from the central optical axis.

[0013] Furthermore, in the image drawn on the front surface of the calibration board, the spatial calibration pattern is two mutually perpendicular dashed lines passing through the central optical axis point; the quadrant symbols are the numerical symbols "1", "2", "3" and "4". The quadrant is a Cartesian coordinate system divided into four regions with the central optical axis point as the origin and the two mutually perpendicular dashed lines in the spatial calibration pattern as the dividing lines: the upper right is quadrant "1", the upper left is quadrant "2", the lower left is quadrant "3", and the lower right is quadrant "4".

[0014] A joint calibration method for ophthalmic multimodal imaging includes the following steps:

[0015] (1) Place the calibration device at the optimal working distance of the calibration device I, start the calibration device I, and image the calibration board in the calibration device to obtain image I of the calibration board;

[0016] (2) Place the calibration device at the optimal working distance of the device to be calibrated II, start the device to be calibrated II, and image the calibration board in the calibration device to obtain image II of the calibration board;

[0017] (3) Observe whether the order of the quadrant symbols of Image I and Image II is correct. If it is not correct, adjust the structural parameters of the calibration equipment I and the calibration equipment II respectively so that the quadrant orientation of Image I and Image II is correct.

[0018] (4) Calculate the displacement Δ and rotation angle θ between the spatial calibration patterns in Image I and Image II respectively, and adjust the structural parameters of the calibration device I or the calibration device II according to the displacement Δ and rotation angle θ so that there is no displacement transformation or rotation transformation between the images formed by the two calibration devices.

[0019] (5) Measure the imaging field of view of the two calibrated devices according to the field of view scale in Image I and Image II respectively, and mark the imaging position boundary and common imaging area according to the imaging field of view of the two calibrated devices.

[0020] (6) Calculate the scaling factor β based on the field of view values ​​of the field of view scale in Image I and Image II, and apply the scaling factor β to Image I or Image II to ensure that Image I and Image II have the same pixel scale.

[0021] Furthermore, in step (3), the quadrant orientation is correct, meaning that in image I and image II, the upper right is quadrant 1, the upper left is quadrant 2, the lower left is quadrant 3, and the lower right is quadrant 4. That is, in image I and image II, the quadrant symbols are "1" for the upper right, "2" for the upper left, "3" for the lower left, and "4" for the lower right.

[0022] Furthermore, in step (4), the displacement Δ and rotation angle θ between the spatial calibration patterns in image I and image II are calculated. The calculation results are obtained by comparing and analyzing the two mutually perpendicular dotted lines of the calibration patterns in image I and image II.

[0023] Furthermore, in step (5), the imaging field of view of the two calibrated devices is measured by observing the maximum scale displayed on the field of view scale in image I and image II, with a measurement accuracy of 1 degree.

[0024] Further, in step (6), the scaling factor β is calculated based on the field-of-view values ​​of the field-of-view scales in image I and image II. The calculation formula is as follows: In the formula N ⅠN represents the number of pixels within the common imaging region in image I. Ⅱ This represents the number of pixels within the common imaging region in image II.

[0025] Compared with the prior art, this patent application has the following advantages:

[0026] 1. This ophthalmic multimodal imaging joint calibration device and method achieves high-precision alignment between fundus cameras and ophthalmic OCT equipment through precise calibration. It effectively solves the spatial matching problem of fundus camera and ophthalmic OCT imaging data, significantly improving imaging accuracy and data consistency, simplifying operation procedures, reducing costs, and enhancing equipment compatibility. Its joint calibration mechanism ensures that both devices operate in the same coordinate system, reducing misdiagnosis caused by imaging data mismatch and effectively reducing the time cost for doctors in multi-device data analysis. It provides doctors with more comprehensive ocular information, improves diagnostic accuracy, and optimizes user experience, demonstrating significant clinical and application value.

[0027] 2. This application uses a central optical axis point d0, a spatial calibration pattern d1, a field of view scale d2, and a quadrant symbol d4 drawn on the front surface of the calibration plate D. The maximum imaging field of view can be obtained by observing the maximum scale displayed on the field of view scale d2 in the image of the calibrated equipment. The measurement accuracy is 1 degree, and the calibration process is time-saving and labor-saving.

[0028] 3. The calibration device includes a variable aperture, an eye-like lens, a water chamber, and a calibration plate. The variable aperture simulates the human pupil, the eye-like lens simulates the human cornea and lens, the water chamber simulates the human eye's water chamber, and the calibration plate simulates the human fundus. The calibration device has optical performance essentially the same as a normal human eye, thus enabling relatively realistic imaging and calibration of fundus camera equipment and ophthalmic OCT equipment. Attached Figure Description

[0029] The present invention can be further illustrated by the non-limiting embodiments given in the accompanying drawings;

[0030] Figure 1 This is a schematic diagram of the calibration device in an embodiment of the ophthalmic multimodal imaging joint calibration device and calibration method of the present invention;

[0031] Figure 2 This is a schematic diagram of the calibration board in the embodiments of the ophthalmic multimodal imaging joint calibration device and calibration method of the present invention;

[0032] The symbols in the diagram are explained as follows:

[0033] A variable aperture, B an eye-like lens, C a water chamber, D a calibration board, d0 a central optical axis point, d1 a spatial calibration pattern, d2 a field of view scale, and d4 a quadrant symbol. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0035] Example 1

[0036] like Figure 1 and Figure 2 As shown, the ophthalmic multimodal imaging joint calibration device of the present invention includes a variable aperture A, an eye-like lens B, a water chamber C, and a calibration plate D.

[0037] In this embodiment, the variable aperture A, the simulated eye lens B, the water chamber C, and the calibration plate D are placed coaxially in sequence. The variable aperture A is placed on the front surface of the simulated eye lens B, which is positioned at the optimal working distance of the device being calibrated. The calibration plate D is placed at the rear focal plane of the simulated eye lens B, and the water chamber C is located in the area between the front surface of the calibration plate D and the rear surface of the simulated eye lens B. The water chamber C is a hollow cylinder, and the front surface of the calibration plate D, the rear surface of the simulated eye lens B, and the water chamber C together form a sealed space, which can be injected with liquid.

[0038] Preferably, the variable aperture A simulates the human eye pupil and is mainly used to control the amount of light transmitted, with its aperture diameter adjustable from 2mm to 8mm. This design allows the calibration device to have optical characteristics that are essentially consistent with those of a real human eye, improving the universality of the calibration device. In practice, the aperture diameter range can also be appropriately enlarged or reduced according to actual needs.

[0039] Preferably, the biomimetic lens B simulates the cornea and lens of the human eye. Based on the refractive power of a normal human eye and the depth of the aqueous humor, the back focal length of the biomimetic lens B is set to 16.6 mm. Considering the significant differences in the operating wavelengths of various calibrated devices, the biomimetic lens B is designed as an optical glass lens with an operating wavelength of 400 nm to 1200 nm. This design ensures that the calibrated ophthalmic equipment can form images correctly. In practice, the back focal length and operating wavelength of the biomimetic lens B can be specifically considered according to actual needs.

[0040] Preferably, the water chamber C simulates the water chamber of the human eye, and its shape is a hollow cylinder. The front surface of the calibration plate D, the rear surface of the eye-like lens B, and the water chamber C together form a sealed space, which can be injected with purified water or physiological saline. This design allows the calibration device to have optical characteristics that are essentially consistent with those of a real human eye, improving the universality of the calibration device. In practice, the type and composition of the liquid injected into the water chamber C can also be considered according to actual needs.

[0041] Preferably, the calibration plate D simulates the human retina and is a circular transparent glass plate with a diameter greater than 20 mm. The front surface of the calibration plate D is decorated with a central optical axis point d0, a spatial calibration pattern d1, a field of view scale d2, and quadrant symbols d4. All graphics on the front surface of the calibration plate D are drawn using a low-reflection material and are painted in black. This design meets the needs of calibration and is suitable for various types of ophthalmic imaging equipment. In practice, the pigment used for drawing the graphics and the material of the calibration plate D can be considered according to specific needs.

[0042] Preferably, the field-of-view scale d2 is a four-segment scale of equal length with the central optical axis point d0 as the center of symmetry. The scale has 51 graduations, each representing 1 degree, and the field-of-view measurement range is 10° to 60°. The graduations are drawn according to the formula Y = f × tan w, where Y is the half-field-of-view height, f is the effective focal length, and w is the half-field-of-view angle. The effective focal length of this calibration device is f = 16.6 mm. Substituting the half-field-of-view angle of 10° to 60° into the formula yields the corresponding scale line positions as 1.45 mm to 9.58 mm (distance from the graduation line to the central optical axis point d0). The graduations are denser near the central optical axis point d0 and sparser further away. This design not only allows for measuring the imaging field of view of the calibrated device but also for calculating the scaling ratio. In practice, the shape of the field-of-view scale d2 can also be considered based on specific circumstances.

[0043] Preferably, in the image drawn on the front surface of the calibration plate D, the spatial calibration pattern d1 consists of two mutually perpendicular dashed lines passing through the central optical axis point d0; the quadrant symbols d4 are the numerical symbols "1", "2", "3", and "4". The quadrants are defined by dividing the Cartesian coordinate system into four regions with the central optical axis point d0 as the origin and the two mutually perpendicular dashed lines in the spatial calibration pattern d1 as the dividing lines: upper right quadrant "1", upper left quadrant "2", lower left quadrant "3", and lower right quadrant "4". This design can calibrate spatial transformation differences such as displacement, rotation, and scaling between different imaging optical paths, and can also calibrate the imaging orientation. In practice, the shape of the graphic drawn on the front surface of the calibration plate D can also be considered according to the specific circumstances.

[0044] Example 2

[0045] The calibration method of the present invention uses a calibration device as a tool to perform calibration work on fundus camera equipment and ophthalmic OCT equipment, and the calibration method includes the following steps:

[0046] (1) Place the calibration device at the optimal working distance of the calibration device I, start the calibration device I, and image the calibration board D in the calibration device to obtain image I of the calibration board D;

[0047] (2) Place the calibration device at the optimal working distance of the calibration device II, start the calibration device II, and image the calibration board D in the calibration device to obtain the image II of the calibration board D;

[0048] (3) Observe whether the order of quadrant symbols d4 in Image I and Image II is correct. If it is not correct, adjust the structural parameters of the calibration equipment I and the calibration equipment II respectively so that the quadrant orientation of Image I and Image II is correct.

[0049] (4) Calculate the displacement Δ and rotation angle θ between the spatial calibration patterns d1 in image I and image II respectively, and adjust the structural parameters of calibration device I or calibration device II according to the displacement Δ and rotation angle θ so that there is no displacement transformation or rotation transformation between the images formed by the two calibration devices.

[0050] (5) Measure the imaging field of view of the two calibrated devices according to the field of view scale d2 in Image I and Image II respectively, and mark the imaging position boundary and common imaging area according to the imaging field of view of the two calibrated devices.

[0051] (6) Calculate the scaling factor β based on the field of view values ​​of the field of view scale d2 in Image I and Image II, and apply the scaling factor β to Image I or Image II to ensure that Image I and Image II have the same pixel scale.

[0052] Preferably, step (3) ensures that the quadrant orientations of both Image I and Image II are correct. Correct quadrant orientation means that in Image I and Image II, the upper right is quadrant 1, the upper left is quadrant 2, the lower left is quadrant 3, and the lower right is quadrant 4. That is, the quadrant symbol d4 in Image I and Image II is "1" in the upper right, "2" in the upper left, "3" in the lower left, and "4" in the lower right. This design ensures that the orientations of the images generated by the two calibration devices are consistent, providing an azimuth reference for subsequent calibration parameter measurements.

[0053] Preferably, in step (4), the displacement Δ and rotation angle θ between the spatial calibration patterns d1 in image I and image II are calculated. The calculation results are obtained by comparing and analyzing the two mutually perpendicular dashed lines of calibration patterns d1 in image I and image II, which is a rigid transformation. This design can ensure the spatial consistency of the images formed by the two calibration devices.

[0054] Preferably, in step (5), the imaging field of view of the two calibrated devices is measured by observing the maximum scale displayed on the field of view scale d2 in image I and image II, with a measurement accuracy of 1 degree. This design can determine the maximum imaging field of view of the two calibrated devices and sequentially determine the common imaging area.

[0055] Preferably, in step (6), the scaling factor β is calculated based on the field-of-view values ​​of the field-of-view scale d2 in image I and image II, and the calculation formula is as follows: In the formula N Ⅰ N represents the number of pixels within the common imaging region in image I. Ⅱ This represents the number of pixels within the common imaging area in Image II. In practical use, the scaling factor β needs to be applied to either Image I or Image II to ensure that Image I and Image II have the exact same image scale; that is, the physical size represented by a single pixel in Image I is the same as the physical size represented by a single pixel in Image II.

[0056] This calibration method uses a calibration device to calibrate fundus camera equipment and ophthalmic OCT equipment. The method first calibrates the image orientation of the images obtained from the two imaging devices, then corrects for displacement and rotation transformations between the images, and finally measures the imaging field of view of both devices and the scaling ratio of the two images. This ensures high spatial matching of the imaging data when the two modal instruments are used for combined imaging.

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An ophthalmic multimodal imaging joint calibration device, characterized in that, Includes a variable aperture (A), an eye-like lens (B), a water chamber (C), and a calibration board (D); The variable aperture (A), the simulated eye lens (B), the water chamber (C), and the calibration plate (D) are placed coaxially in sequence. The variable aperture (A) is placed on the front surface of the simulated eye lens (B), which is placed at the optimal working distance of the device being calibrated. The calibration plate (D) is placed at the back focal plane of the simulated eye lens (B). The water chamber (C) is located in the area between the front surface of the calibration plate (D) and the back surface of the simulated eye lens (B). The water chamber (C) is a hollow cylinder. The front surface of the calibration plate (D), the back surface of the simulated eye lens (B), and the water chamber (C) together form a sealed space, which is filled with liquid. The variable aperture (A) simulates the human eye pupil and is mainly used to control the amount of light passing through. Its light-passing aperture adjustment range is 2mm~8mm. The simulated eye lens (B) simulates the cornea and lens of the human eye, with a back focal length of 16.6mm; the simulated eye lens (B) is an optical glass lens with a working wavelength of 400nm~1200nm; The water chamber (C) simulates the water chamber of the human eye. It is a hollow cylinder. The front surface of the calibration plate (D), the rear surface of the simulated eye lens (B), and the water chamber (C) together form a sealed space, which can be injected with pure water or physiological saline. The calibration plate (D) simulates the human retina. The calibration plate (D) is a circular transparent glass plate with a diameter greater than 20 mm. The front surface of the calibration plate (D) is drawn with the central optical axis point (d0), spatial calibration pattern (d1), field of view scale (d2) and quadrant symbol (d4). All graphics on the front surface of the calibration plate (D) are drawn with a low-reflection material and the drawing color is black. The field-of-view scale (d2) consists of four equal-length segments symmetrically centered on the central optical axis (d0). The scale has 51 graduations, each representing 1 degree, and the field-of-view measurement range is 10° to 60°. The graduations are calculated according to the formula... The drawing, in the style Y At half the field of view height, f For the effective focal length, w Half field of view; effective focal length f= 16.6mm, the scale lines are denser near the central optical axis point (d0) and sparser further away from the central optical axis point (d0); In the image drawn on the front surface of the calibration plate (D), the spatial calibration pattern (d1) is two mutually perpendicular dashed lines passing through the central optical axis point (d0); the quadrant symbols (d4) are the numerical symbols "1", "2", "3" and "4". The quadrant is a Cartesian coordinate system divided into four regions with the central optical axis point (d0) as the origin and the two mutually perpendicular dashed lines in the spatial calibration pattern (d1) as the dividing lines: the upper right is quadrant "1", the upper left is quadrant "2", the lower left is quadrant "3", and the lower right is quadrant "4".

2. A method for joint calibration of ophthalmic multimodal imaging, said calibration method being based on the calibration device of claim 1, characterized in that, Includes the following steps: (1) Place the calibration device at the optimal working distance of the calibration device I, start the calibration device I, and image the calibration board (D) in the calibration device to obtain image I of the calibration board (D); (2) Place the calibration device at the optimal working distance of the calibration device II, start the calibration device II, and image the calibration board (D) in the calibration device to obtain image II of the calibration board (D); (3) Observe whether the order of quadrant symbols (d4) of image I and image II is correct. If it is not correct, adjust the structural parameters of the calibration equipment I and calibration equipment II respectively so that the quadrant orientation of image I and image II is correct. (4) Calculate the displacement Δ and rotation angle θ between the spatial calibration patterns (d1) in image I and image II respectively, and adjust the structural parameters of calibration device I or calibration device II according to the displacement Δ and rotation angle θ so that there is no displacement transformation or rotation transformation between the images formed by the two calibration devices. (5) Measure the imaging field of view of the two calibrated devices according to the field of view scale (d2) in Image I and Image II respectively, and mark the imaging position boundary and common imaging area according to the imaging field of view of the two calibrated devices. (6) Calculate the scaling factor β based on the field of view values ​​of the field of view scale (d2) in Image I and Image II, and apply the scaling factor β to Image I or Image II to ensure that Image I and Image II have the same pixel scale.

Images