Ophthalmology multimodal imaging combined calibration device and calibration method

Abstract

The invention relates to an ophthalmic multi-mode imaging combined calibration device and calibration method. The device comprises a variable diaphragm, an eye-imitating lens, a water chamber and a calibration plate, the eye-imitating lens is placed at the optimal working distance of the equipment to be calibrated; the iris diaphragm is placed on the front surface of the eye-imitating lens, and the clear aperture of the iris diaphragm can be adjusted at will; the calibration plate is placed on the rear focal plane of the eye-imitating 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-imitating lens and the water chamber form a closed space in which liquid can be injected. The method is mainly used for combined imaging calibration of fundus camera equipment and ophthalmology OCT equipment, and solves the problem of poor spatial matching of imaging data during combined imaging of two modal instruments.

Description

Technical Field

[0001] The present invention belongs to the field of ophthalmic optical imaging, and relates to an ophthalmic multimodal imaging joint calibration device and a calibration method, and in particular to a joint imaging calibration of a fundus camera device and an ophthalmic OCT device. Background Art

[0002] The physiological structure of the human eye is complex, and examination of the retina can accurately diagnose a variety of eye diseases and systemic diseases. At present, the commonly used fundus imaging technologies in clinical practice mainly include ophthalmoscopes, fundus cameras, laser scanning ophthalmoscopes, and optical coherence tomography (OCT). However, in the actual clinical diagnosis and treatment process, relying solely on single-modality imaging data for auxiliary diagnosis has obvious limitations and is difficult to 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 them, the combined application of fundus cameras and ophthalmic OCT has played an important 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 diagnosis and misdiagnosis, but also provides more comprehensive and accurate fundus disease assessment information.

[0003] However, the joint examination of fundus camera and ophthalmic OCT faces a key problem, namely the poor spatial matching of imaging data. Since fundus camera and ophthalmic OCT are two relatively independent optical imaging systems, equipment installation errors and mechanical structure deviations may lead to inconsistent imaging positions, resulting in spatial transformation differences such as displacement, rotation and scaling between the imaging data of the two modalities, and there are also significant differences in the field of view of the two modalities. These problems make it difficult to directly compare or integrate the images of the two modalities for diagnosis, which not only increases the possibility of misdiagnosis and missed diagnosis, but also brings great technical challenges to retinal three-dimensional reconstruction and subsequent medical image processing. In addition, for the calibration device in the prior art, the maximum imaging field of view needs to be manually calculated based on the half field of view angle, and the calibration process is time-consuming and labor-intensive. Summary of the invention

[0004] The purpose of the present invention is to provide an ophthalmic multimodal imaging joint calibration device and a calibration method to realize the joint imaging calibration of a fundus camera device and an ophthalmic OCT device, and to solve the problem of poor spatial matching of imaging data when two modality instruments are jointly imaged.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is as follows:

[0006] An ophthalmic multimodal imaging joint calibration device comprises a variable aperture, an artificial eye lens, a water chamber and a calibration plate.

[0007] Furthermore, the variable iris, the imitation eye lens, the water room and the calibration plate are coaxially placed in sequence, the variable iris is placed on the front surface of the imitation eye lens, the imitation eye lens is placed at the optimal working distance of the calibrated device, the calibration plate is placed at the rear focal plane of the imitation eye lens, and the water room is located in the area between the front surface of the calibration plate and the rear surface of the imitation eye lens. The water room is a hollow cylinder, and the front surface of the calibration plate, the rear surface of the imitation eye lens and the water room together form a closed space, and liquid can be injected into the interior.

[0008] Furthermore, the variable iris simulates the pupil of a human eye and is mainly used to control the amount of light passing through, and the adjustment range of the light passing aperture is 2 mm to 8 mm.

[0009] Furthermore, the artificial eye lens simulates the cornea and lens of a human eye, and has a back focal length of 16.6 mm; the artificial eye lens is an optical glass lens, and its operating band is 400 nm to 1200 nm.

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

[0011] Furthermore, the calibration plate simulates the retina of the human eye. The calibration plate is a round transparent glass sheet with a diameter greater than 20 mm. The central optical axis point, spatial calibration pattern, field of view scale and quadrant symbol are drawn on the front surface of the calibration plate. All graphics on the front surface of the calibration plate are drawn with low-reflective material and the drawing color is black.

[0012] Furthermore, the field of view scale is a four-section equal-length scale with the central optical axis point as the symmetry center. There are 51 scale lines drawn on the scale, each scale line represents 1 degree, and the field of view measurement range is 10° to 60°; the scale lines of the scale are drawn according to the formula Y=f×tanw, 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=16.6mm, and the scale lines of the scale are denser near the central optical axis point and sparser away from the central optical axis point.

[0013] Furthermore, in the image drawn on the front surface of the calibration plate, the spatial calibration pattern is two mutually perpendicular dotted lines passing through the central optical axis point; the quadrant symbols are the digital symbols "1", "2", "3" and "4", and the quadrant takes the central optical axis point as the origin and the two mutually perpendicular dotted lines in the spatial calibration pattern as the dividing lines, dividing the plane rectangular coordinate system into four areas: 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] The ophthalmic multimodal imaging joint calibration method comprises the following steps:

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

[0016] (2) placing the calibration device at the optimal working distance of the device to be calibrated II, starting the device to be calibrated II, imaging the calibration plate in the calibration device, and obtaining an image of the calibration plate II;

[0017] (3) Observe whether the order of the quadrant symbols of image I and image II is correct. If not, adjust the structural parameters of the calibrated device I and the calibrated device II respectively to make the quadrant orientations of image I and image II correct;

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

[0019] (5) Measure the imaging fields of the two calibrated devices respectively according to the field of view scales in Image I and Image II, and calibrate the imaging position boundaries and the common imaging area according to the imaging fields of the two calibrated devices;

[0020] (6) Calculate the scaling ratio β according to the field of view values ​​of the field of view scales in image I and image II, and apply the scaling ratio β to image I or image II to ensure that image I and image II have exactly the same pixel scale.

[0021] Furthermore, the correct orientation of the quadrants in step (3) 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 symbols in image I and image II are "1" in the upper right, "2" in the upper left, "3" in the lower left, and "4" in the lower right.

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

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

[0024] Furthermore, in step (6), the scaling ratio β is calculated based on the field of view values ​​of the field of view scales in image I and image II, and the calculation formula is: Where N Ⅰis the number of pixels in the common imaging area in image I, N Ⅱ is the number of pixels in the common imaging area in image II.

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

[0026] 1. The ophthalmic multimodal imaging joint calibration device and method achieves high-precision alignment of the fundus camera and the ophthalmic OCT device through precise calibration, which can effectively solve the spatial matching problem of the fundus camera and the ophthalmic OCT imaging data, significantly improve the imaging accuracy and data consistency, simplify the operation steps, reduce costs, and enhance the compatibility of equipment. Its joint calibration mechanism ensures that the two devices work in the same coordinate system, reduces misdiagnosis due to mismatched imaging data, and effectively reduces the time cost of doctors in multi-device data analysis, providing doctors with more comprehensive eye information, improving diagnostic accuracy, and optimizing user experience, with significant clinical and application value.

[0027] 2. In this application, the central optical axis point d0, the spatial calibration pattern d1, the field of view scale d2 and the quadrant symbol d4 are drawn on the front surface of the calibration plate D. The maximum imaging field of view range can be obtained by observing the maximum scale displayed by the field of view scale d2 in the image of the calibrated device. The measurement accuracy is 1 degree, and the calibration process saves time and effort.

[0028] 3. The calibration device includes a variable iris, an eye-like lens, a water chamber and a calibration plate, wherein the variable iris simulates the pupil of the human eye, the eye-like lens simulates the cornea and lens of the human eye, the water chamber simulates the water chamber of the human eye, and the calibration plate simulates the fundus of the human eye. The calibration device has basically the same optical performance as a normal human eye, so that fundus camera equipment and ophthalmic OCT equipment can be imaged and calibrated more realistically. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0031] Figure 2 This is a calibration plate in the embodiment 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] Variable aperture A, imitation eye lens B, water room C, calibration plate D, central optical axis point d0, space calibration pattern d1, field of view scale d2 and quadrant symbol d4. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, the technical solution of the present invention is 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 imitation eye lens B, a water chamber C and a calibration plate D.

[0037] In this embodiment, the variable iris A, the imitation eye lens B, the water chamber C and the calibration plate D are coaxially placed in sequence, the variable iris A is placed on the front surface of the imitation eye lens B, the imitation eye lens B is placed at the optimal working distance of the calibrated device, the calibration plate D is placed at the rear focal plane of the imitation 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 imitation 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 imitation eye lens B and the water chamber C together form a closed space, and liquid can be injected into the interior.

[0038] Preferably, the variable aperture A simulates the pupil of the human eye and is mainly used to control the amount of light passing through, and the aperture adjustment range is 2 mm to 8 mm. Such a design can make the calibration device basically consistent with the optical characteristics of the real human eye, and improve the universality of the calibration device. In fact, the aperture range can also be appropriately expanded or reduced according to actual needs.

[0039] Preferably, the imitation eye lens B simulates the human cornea and lens, and according to the refractive power of the normal human eye and the depth of the human eye's aqueous chamber, the back focal length of the imitation eye lens B is set to 16.6 mm; considering that the working light bands of various calibrated devices are quite different, the imitation eye lens B is designed to be an optical glass lens, and its working band is 400nm to 1200nm. Such a design can ensure that the calibrated ophthalmic device can form an image normally. In fact, the back focal length and working band of the imitation eye lens B can also be specifically considered according to actual needs.

[0040] Preferably, the water chamber C simulates the water chamber of the human eye and is in the shape of a hollow cylinder. The front surface of the calibration plate D, the rear surface of the imitation eye lens B and the water chamber C together form a closed space, into which pure water or physiological saline can be injected. Such a design can make the calibration device basically consistent with the optical properties of the real human eye, and improve the universality of the calibration device. In fact, the type and composition of the liquid injected into the water chamber C can also be specifically considered according to actual needs.

[0041] Preferably, the calibration plate D simulates the retina of the human eye, and the calibration plate D is a round transparent glass sheet with a diameter greater than 20 mm; the central optical axis point d0, the spatial calibration pattern d1, the field of view scale d2 and the quadrant symbol d4 are drawn on the front surface of the calibration plate D, and all the graphics on the front surface of the calibration plate D are drawn with low-reflective materials, and the drawing color is black. Such a design can meet the needs of calibration and calibration, and is suitable for various types of ophthalmic imaging equipment. In fact, the pigment for drawing the graphics and the material of the calibration plate D can also be specifically considered according to actual needs.

[0042] Preferably, the field of view scale d2 is a four-segment scale with the central optical axis point d0 as the symmetry center. There are 51 scale lines drawn in the scale, each scale line represents 1 degree, and the field of view measurement range is 10°~60°; the scale lines of the scale are drawn according to the formula Y=f×tanw, 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=16.6mm of this calibration device, and the corresponding scale line position of 1.45mm~9.58mm (the distance from the scale line to the central optical axis point d0) can be obtained by substituting the half field of view angle 10o~60o into the above formula. The scale lines of the scale are denser near the central optical axis point d0, and sparser away from the central optical axis point d0. Such a design can not only measure the imaging field of view range of the calibrated equipment, but also calculate the scaling ratio. In fact, the shape of the field of view scale d2 can also be specifically considered according to actual conditions.

[0043] Preferably, in the image drawn on the front surface of the calibration plate D, the spatial calibration pattern d1 is two mutually perpendicular dotted lines passing through the central optical axis point d0; the quadrant symbol d4 is the digital symbols "1", "2", "3" and "4", and the quadrant is the central optical axis point d0 as the origin, and the two mutually perpendicular dotted lines in the spatial calibration pattern d1 are used as dividing lines, dividing the plane rectangular coordinate system into four areas: 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". Such a design can calibrate the differences in spatial transformations such as displacement, rotation and scaling between different imaging optical paths, and can also calibrate the imaging orientation. In fact, the shape of the figure drawn on the front surface of the calibration plate D can also be specifically considered according to actual conditions.

[0044] Example 2

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

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

[0047] (2) placing the calibration device at the optimal working distance of the device to be calibrated II, starting the device to be calibrated II, imaging the calibration plate D in the calibration device, and obtaining an image II of the calibration plate D;

[0048] (3) Observe whether the order of the quadrant symbol d4 of image I and image II is correct. If not, adjust the structural parameters of the calibrated device I and the calibrated device II respectively to make the quadrant orientation of image I and image II correct;

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

[0050] (5) The imaging fields of view of the two calibrated devices are measured according to the field of view scale d2 in image I and image II, respectively, and the imaging position boundaries and the common imaging area are calibrated according to the imaging fields of view of the two calibrated devices.

[0051] (6) Calculate the scaling ratio β according to the field of view values ​​of the field of view scale d2 in image I and image II, and apply the scaling ratio β to image I or image II to ensure that image I and image II have exactly the same pixel scale.

[0052] Preferably, the function of step (3) is to ensure that the quadrant orientations of both image I and image II are correct, and the 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. Such a design can ensure that the orientations of the images formed by the two calibrated devices are consistent, providing an orientation reference for the subsequent measurement of calibration parameters.

[0053] Preferably, the displacement Δ and rotation angle θ between the spatial calibration pattern d1 in image I and image II are calculated in step (4), and the calculation result is obtained by comparing and analyzing the two mutually perpendicular imaginary lines of the calibration pattern d1 in image I and image II, which belongs to rigid transformation. Such a design can ensure the consistency of the spatial position of the images formed by the two calibrated devices.

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

[0055] Preferably, in step (6), the scaling ratio 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: Where N Ⅰ is the number of pixels in the common imaging area in image I, N Ⅱ is the number of pixels in the common imaging area of ​​image II. When the two calibrated devices are actually used, the scaling ratio β needs to be applied to image I or image II to ensure that image I and image II have exactly the 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 as a tool to calibrate fundus camera equipment and ophthalmic OCT equipment. This calibration method first calibrates the image orientation of the images formed by the two imaging devices, then corrects the displacement transformation and rotation transformation between the images formed by the two imaging devices, and finally measures the imaging field of view range of the two imaging devices and the scaling ratio of the two images, thereby ensuring that the imaging data of the two modal instruments have a high spatial matching when jointly imaging.

[0057] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed by 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: It includes variable aperture (A), imitation eye lens (B), water room (C) and calibration plate (D).

2. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The variable aperture (A), the imitation eye lens (B), the water chamber (C) and the calibration plate (D) are coaxially placed in sequence, the variable aperture (A) is placed on the front surface of the imitation eye lens (B), the imitation eye lens (B) is placed at the optimal working distance of the calibrated device, the calibration plate (D) is placed at the rear focal plane of the imitation 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 imitation 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 imitation eye lens (B) and the water chamber (C) together form a closed space, and liquid is injected inside.

3. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The variable iris (A) simulates the pupil of a human eye and is mainly used to control the amount of light passing through. The adjustment range of the aperture of the variable iris (A) is 2 mm to 8 mm.

4. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The imitation eye lens (B) simulates the cornea and lens of a human eye, and has a back focal length of 16.6 mm. The imitation eye lens (B) is an optical glass lens, and has a working wavelength range of 400 nm to 1200 nm.

5. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The water chamber (C) simulates the water chamber of a human eye and is in the shape of a hollow cylinder. The front surface of the calibration plate (D), the rear surface of the imitation eye lens (B) and the water chamber (C) together form a closed space, into which pure water or physiological saline can be injected.

6. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The calibration plate (D) simulates the retina of the human eye. The calibration plate (D) is a circular transparent glass sheet with a diameter greater than 20 mm. The front surface of the calibration plate (D) is drawn with a central optical axis point (d0), a spatial calibration pattern (d1), a field of view scale (d2) and a quadrant symbol (d4). All graphics on the front surface of the calibration plate (D) are drawn with a low-reflective material and the drawing color is black.

7. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: The field of view scale (d2) is a four-section equal-length scale with the central optical axis point (d0) as the symmetry center. A total of 51 scale lines are drawn on the scale, each scale line represents 1 degree, and the field of view measurement range is 10° to 60°; the scale lines of the scale are drawn according to the formula Y=f×tanw, 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=16.6mm, and the scale lines of the scale are denser near the central optical axis point (d0) and sparser away from the central optical axis point (d0).

8. The ophthalmic multimodal imaging joint calibration device according to claim 1, characterized in that: In the image drawn on the front surface of the calibration plate (D), the spatial calibration pattern (d1) is two mutually perpendicular dotted lines passing through the central optical axis point (d0); the quadrant symbols (d4) are digital symbols "1", "2", "3" and "4", and the quadrant is a plane rectangular coordinate system divided into four areas with the central optical axis point (d0) as the origin and the two mutually perpendicular dotted 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".

9. An ophthalmic multimodal imaging joint calibration method, the calibration method being based on the calibration device according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) placing the calibration device at the optimal working distance of the device to be calibrated I, starting the device to be calibrated I, imaging the calibration plate (D) in the calibration device, and obtaining an image I of the calibration plate (D); (2) placing the calibration device at the optimal working distance of the device to be calibrated II, starting the device to be calibrated II, imaging the calibration plate (D) in the calibration device, and obtaining an image II of the calibration plate (D); (3) Observe whether the order of the quadrant symbols (d4) of image I and image II is correct. If not, adjust the structural parameters of the calibrated device I and the calibrated device II respectively to make the quadrant orientations of image I and image II correct; (4) respectively calculating the displacement Δ and the rotation angle θ between the spatial calibration pattern (d1) in image I and image II, and adjusting the structural parameters of the calibrated device I or the calibrated device II according to the displacement Δ and the rotation angle θ, so that there is no displacement transformation and rotation transformation between the images formed by the two calibrated devices; (5) Measure the imaging fields of the two calibrated devices respectively according to the field of view scales (d2) in Image I and Image II, and calibrate the imaging position boundaries and the common imaging area according to the imaging fields of the two calibrated devices; (6) Calculate the scaling factor β according to 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 exactly the same pixel scale.

Images