Automated Fundus Examination Device and Auto-Focusing Method Applied to Diabetic Retinopathy Screening

Abstract

The present invention relates to an automated fundus examination device applied to the screening of diabetic retinopathy, which includes an eyepiece, a beam splitter, a fundus camera system, an OCT system and a reference arm system. The fundus camera system and the OCT system share the eyepiece as the main optical path. The fundus retina and the intermediate image plane are conjugate. It is divided into two independent sub-optical paths by the beam splitter. These two sub-optical paths are the sub-optical path formed by the fundus camera system and the sub-optical path formed by the OCT system and the reference arm system. The present invention also relates to an autofocus method, which includes automatic search for the reference position, refractive compensation and focusing of the fundus camera. The fundus camera system and the OCT system of the present invention can simultaneously obtain fundus photos and fundus tomographic scan images, providing a more powerful diagnostic basis for the screening of diabetic retinopathy. The present invention can also realize the automatic adjustment of the fundus camera system and the OCT system, without additional optical elements, having no influence on the main optical system, with high repeatability and fast focusing speed.

Description

Technical Field

[0001] The present invention belongs to the field of medical devices, and relates to a fundus examination device, specifically an automated fundus examination device and an autofocus method applied to the screening of diabetic retinopathy. Background Art

[0002] Diabetic retinopathy, abbreviated as "diabetic retinopathy", is a disease caused by diabetes that can lead to retinal vascular disorders. It is the main cause of blindness in diabetic patients, and the incidence of the disease increases with the duration of diabetes. Therefore, timely popularization of diabetic retinopathy screening and treatment intervention for early-stage diabetic patients can effectively reduce the risk of blindness caused by diabetes.

[0003] Fundus cameras are currently the most widely used technical means for diabetic retinopathy screening. Traditional fundus cameras can provide information on retinal lesions and bleeding in patients, but they cannot diagnose deep retinal lesions, which may lead to missed or misdiagnosed cases of early diabetic retinopathy and delay treatment. Non-mydriatic fundus camera OCT (optical coherence tomography) products can solve this problem by expanding diabetic retinopathy diagnosis from a two-dimensional level to a three-dimensional level and providing both fundus photos and fundus tomographic images. To obtain high-quality fundus examination results, it is necessary to adjust the focusing parameters of the device according to the patient's condition and perform refractive compensation. In the past, most adjustments were made manually, which was time-consuming, complex, and inconvenient to operate, and it was difficult to meet the requirements of modern rapid examinations.

[0004] Patent CN203709995 describes a fundus autofocus compensation device that adds a sub-optical path to the optical path and realizes autofocus by calculating the clarity of fundus images. This method increases the complexity of the system, and due to the large individual differences of the subjects, it is difficult to ensure the repeatability and applicability of focusing. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide an automated fundus examination device applied to the screening of diabetic retinopathy.

[0006] The technical problem of the present invention is solved by the following technical solutions:

[0007] An automated fundus examination device applied to the screening of diabetic retinopathy, including an eyepiece and a beam splitter, characterized in that it further includes a fundus camera system, an OCT system, and a reference arm system. The fundus camera system and the OCT system share the eyepiece as the main optical path. The fundus retina and the intermediate image plane are conjugate. After passing through the beam splitter, it is divided into two independent sub-optical paths, namely the sub-optical path composed of the fundus camera system and the sub-optical path composed of the OCT system and the reference arm system.

[0008] Moreover, the fundus camera system includes a fundus camera imaging objective lens group, a fundus camera image receiver, a fundus camera focusing motor, and a fundus camera focusing screw. On a sub-optical path of the beam splitter, the fundus camera imaging objective lens group and the fundus camera image receiver are sequentially arranged from near to far. The fundus camera imaging objective lens group and the fundus camera image receiver form an image focusing module, which is threadedly connected to the fundus camera focusing screw. The fundus camera focusing screw is driven by the fundus camera focusing motor.

[0009] Moreover, the OCT system includes an OCT refractive compensation screw, an OCT refractive compensation motor, an OCT refractive compensation lens group, a collimator, an OCT sample arm input fiber optic connector, and an OCT signal demodulation system. On the other sub-optical path of the beam splitter, the OCT refractive compensation lens group, the collimator, the OCT sample arm input fiber optic connector, and the OCT signal demodulation system are sequentially arranged from near to far. The OCT refractive compensation screw is threadedly connected to the OCT refractive compensation lens group, and the OCT refractive compensation screw is driven by the OCT refractive compensation motor.

[0010] Moreover, the reference arm system includes an OCT reference arm input fiber optic connector, a reference arm collimator, a reference arm focusing lens, and a reference arm reflector. Behind the OCT signal demodulation system, the OCT reference arm input fiber optic connector, the reference arm collimator, the reference arm focusing lens, and the reference arm reflector are sequentially arranged. The reference arm focusing lens and the reference arm reflector form a reference surface module, which is driven by a screw to move along the optical axis direction to change the actual position of the reference surface.

[0011] An autofocus method for an automated fundus examination device applied to diabetic retinopathy screening, characterized by comprising the following steps:

[0012] Step 1, automatic search for the reference position:

[0013] Move the reference surface module to perform a full scan of the actual position of the reference surface in the entire OCT imaging range to obtain an OCT image corresponding to the reference surface position information;

[0014] Select the reference surface position corresponding to the strongest signal-to-noise ratio, and this reference surface position is the optimal reference surface;

[0015] Moving the reference surface module to the optimal reference surface position can obtain an OCT image with the best signal-to-noise ratio;

[0016] Step 2, refractive compensation:

[0017] When moving the OCT refractive compensation lens group within the design range, the focal position of the incident light will move along the optical axis direction accordingly. When the incident light converges at the retina position, the signal-to-noise ratio of the OCT image is the strongest, and the peak position is the corresponding optimal position for refractive compensation.

[0018] Record this optimal position for refractive compensation, and the OCT refractive compensation motor drives the OCT refractive compensation lens group to move to this optimal position for refractive compensation to complete the automatic refractive compensation of OCT.

[0019] Step 3, focus the fundus camera:

[0020] Feed back the optimal position for refractive compensation to the fundus camera system. The focus motor of the fundus camera drives the imaging objective lens group and the image receiver of the fundus camera to move together. The corresponding relationship between the focus position of the fundus camera and the OCT refractive compensation position is positively correlated. A one-to-one correspondence between the focus position of the fundus camera and the OCT refractive compensation position can be established, or a screw with a linearly proportional pitch can be used to establish a proportional relationship between the focus position of the fundus camera and the OCT refractive compensation position. Find the corresponding focus position of the fundus camera through the known OCT refractive compensation position to complete the automatic focusing of the fundus camera image.

[0021] The advantages and positive effects of the present invention are:

[0022] The fundus camera system and OCT system of the present invention can simultaneously obtain fundus photos and fundus tomographic scan images, providing a more powerful diagnostic basis for the screening of diabetic retinopathy; the present invention can also realize the automatic adjustment of the fundus camera system and OCT system, without additional optical elements, having no impact on the main optical system, high repeatability, and fast focusing speed. Brief Description of the Drawings

[0023] Figure 1 It is a structural schematic diagram of the present invention;

[0024] Figure 2 It is a schematic diagram of the OCT refractive compensation screw of the present invention;

[0025] Figure 3 It is a calculation curve graph for the automatic adjustment of the reference arm of the present invention, where the abscissa represents the reference surface position identifier and the ordinate represents the signal-to-noise ratio intensity;

[0026] Figure 4 It is a calculation curve graph for the automatic adjustment of refractive compensation of the present invention, where the abscissa represents the refractive compensation diopter identifier and the ordinate represents the signal-to-noise ratio intensity.

[0027] Description of the Reference Numerals

[0028] 1 - Fundus retina, 2 - Eyepiece, 3 - Intermediate image plane, 4 - Beam splitter, 5 - Fundus camera imaging objective lens group, 6 - Fundus camera image receiver, 7 - Fundus camera focusing motor, 8 - Fundus camera focusing screw, 9 - OCT refractive compensation screw, 10 - OCT refractive compensation motor, 11 - OCT refractive compensation lens group, 12 - Collimator, 13 - OCT sample arm input fiber optic connector, 14 - OCT signal demodulation system, 15 - OCT reference arm input fiber optic connector, 16 - Reference arm collimator, 17 - Reference arm focusing lens, 18 - Reference arm reflector. Detailed implementation mode

[0029] The following further details the embodiments of the present invention in conjunction with the accompanying drawings. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0030] An automated fundus examination device applied to diabetic retinopathy screening, including an eyepiece 2 and a beam splitter 4. Its innovation lies in: it also includes a fundus camera system, an OCT system, and a reference arm system;

[0031] As Figure 1 shown, the said fundus camera system includes a fundus camera imaging objective lens group 5, a fundus camera image receiver 6, a fundus camera focusing motor 7, and a fundus camera focusing screw 8;

[0032] The said OCT system includes an OCT refractive compensation screw 9, an OCT refractive compensation motor 10, an OCT refractive compensation lens group 11, a collimator 12, an OCT sample arm input fiber optic connector 13, and an OCT signal demodulation system 14;

[0033] The said reference arm system includes an OCT reference arm input fiber optic connector 15, a reference arm collimator 16, a reference arm focusing lens 17, and a reference arm reflector 18; The reference arm focusing lens and the reference arm reflector form a reference surface module, and this reference surface module moves along the optical axis direction driven by a screw to change the actual position of the reference surface.

[0034] The fundus camera system and the OCT system share the eyepiece as the main optical path. The fundus retina 1 and the intermediate image plane 3 are conjugate. Then, it is divided into independent sub - optical paths by the beam splitter. The refractive condition of the measured eye is compensated by calculating the signal - to - noise ratio of the OCT signal, and at the same time, this position is fed back to the fundus camera system for automatic focusing. There is no need to add additional optical elements, which avoids the influence on the optical system and reduces the complexity of the system.

[0035] The fundus retina, the intermediate image plane, and the image receiver of the fundus camera form an optical system conjugate. At this time, the intermediate image plane of the fundus retina coincides with the intermediate image plane 3 of the image receiver of the fundus camera. When the position of the retina changes due to refractive error or other factors, the position of the intermediate image plane of the fundus retina also changes accordingly, moving back and forth along the optical axis, and the two intermediate image planes are separated, that is, a clear image cannot be received on the image receiver of the fundus camera.

[0036] In the fundus camera system, image focusing is jointly completed by the imaging objective lens group of the fundus camera and the image receiver of the fundus camera. The relative positions of the two are guaranteed to be unchanged. As a whole, it is driven by the focusing motor of the fundus camera through the focusing screw of the fundus camera to move along the optical axis. When the above two intermediate image planes coincide, the focusing operation is completed.

[0037] Similarly, in the OCT system, the OCT sample arm uses an optical fiber connector as the input end, which is a point light source. After being collimated by a collimating mirror and expanded into parallel light, it is then converged to the position of the intermediate image plane through the OCT refractive compensation lens group, that is, converged to the fundus retina. At this time, an OCT image with the best signal-to-noise ratio can be obtained. When the position of the intermediate image plane changes, the OCT refractive compensation lens group is driven by the OCT refractive compensation motor through the OCT refractive compensation screw to move along the optical axis direction accordingly, ensuring that the incident light is converged to the position of the intermediate image plane, that is, the position of the fundus retina, to complete refractive compensation.

[0038] Among them, the moving distances of the focusing of the fundus camera and the refractive compensation of the OCT are the same, that is, the distance of the change in the position of the intermediate image plane.

[0039] The implementation process of the automatic focusing adjustment of the present invention is as follows:

[0040] Step 1: Automatic search for the reference position

[0041] In the device of the present invention, the OCT part is used to obtain tomographic images of the human eye and to realize the automatic process of the device. According to the basic principle of OCT, the distance between the position of the human eye and the position of the reference plane is called the optical path difference. When the optical path difference increases, the signal-to-noise ratio of the OCT signal drops rapidly. Move the reference plane module to scan the actual position of the reference plane once in the entire OCT imaging range to obtain a series of OCT images corresponding to the reference plane position information;

[0042] Perform signal-to-noise ratio calculation on the collected OCT image signals, and the curve as shown in Figure 3 can be obtained. Each abscissa counting point corresponds to a reference plane position, and the corresponding ordinate is the signal-to-noise ratio of the signal at this position;

[0043] Select the reference plane position corresponding to the strongest signal-to-noise ratio. This position is the best reference plane;

[0044] At this time, moving the reference plane module to the optimal reference plane position can obtain an OCT image with the best signal-to-noise ratio. Step 2: Refractive compensation

[0045] After the optimal reference plane position is determined, the retinal position shift caused by eye refractive error is compensated. It is also necessary to converge the incident light to the retinal position to further improve the signal-to-noise ratio of the OCT image and obtain a clear fundus photograph.

[0046] When moving the OCT refractive compensation lens group within the design range, the focal position of the incident light will move along the optical axis direction accordingly. The rotation speed of the OCT refractive compensation motor is a, the motor rotation subdivision step number is N, and the pitch of the OCT refractive compensation screw is S (as Figure 2 shown), then the moving speed of the OCT refractive compensation lens group is a*S, and the corresponding position point counting speed of the OCT refractive compensation lens group is a*N; the OCT line acquisition frequency is F, and each frame contains n lines, then the OCT image frame frequency for calculation is F / n; when performing OCT refractive compensation, it is required that a*N >> F / n, that is, each calculated image corresponds to a unique position counting point, ensuring the accuracy and precision of refractive compensation, and the compensation precision is a*S*n / F.

[0047] When moving the OCT refractive compensation lens group within the design range, the focal position of the incident light will move along the optical axis direction accordingly. When the incident light converges at the retinal position, the signal-to-noise ratio of the OCT image is the strongest. From this, the curve as Figure 4 shown can be obtained. The peak position is the corresponding optimal refractive compensation position. Record this optimal refractive compensation position, and the OCT refractive compensation motor drives the OCT refractive compensation lens group to move to this optimal refractive compensation position to complete the OCT automatic refractive compensation.

[0048] Step 3: Focusing of the fundus camera

[0049] Feed back the optimal refractive compensation position to the fundus camera system. The fundus camera focusing motor drives the fundus camera imaging objective lens group and the fundus camera image receiver to move together. The corresponding relationship between the fundus camera focusing position and the OCT refractive compensation position is in a proportional relationship. A one-to-one correspondence between the fundus camera focusing position and the OCT refractive compensation position can be established, or a screw with a linearly proportional pitch can be used to establish a proportional relationship between the fundus camera focusing position and the OCT refractive compensation position. Find the corresponding fundus camera focusing position through the known OCT refractive compensation position to complete the automatic focusing of the fundus camera image.

[0050] In the specific implementation of the present invention, the fundus camera image receiver is a area array light receiving device, which can be a CMOS or a CCD.

[0051] Although embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the content disclosed in the embodiments and drawings.

Claims

1. An automated fundus examination device for diabetic retinopathy screening, comprising an eyepiece and a beam splitter, characterized in that: It also includes a fundus camera system, an OCT system and a reference arm system. The fundus camera system and the OCT system share an eyepiece as the main optical path. The fundus retina and the intermediate image plane are conjugate. It is divided into two independent sub-optical paths by a beam splitter. The two sub-optical paths are the sub-optical path formed by the fundus camera system and the sub-optical path formed by the OCT system and the reference arm system; The described fundus camera system includes a fundus camera imaging objective lens group, a fundus camera image receiver, a fundus camera focusing motor, and a fundus camera focusing screw. On one sub-optical path of the beam splitter, the fundus camera imaging objective lens group and the fundus camera image receiver are sequentially arranged from near to far. The fundus camera imaging objective lens group and the fundus camera image receiver form an image focusing module. The image focusing module is threadedly connected to the fundus camera focusing screw, and the fundus camera focusing screw is driven by the fundus camera focusing motor; The described OCT system includes an OCT refractive compensation screw, an OCT refractive compensation motor, an OCT refractive compensation lens group, a collimator, an OCT sample arm input fiber connector, and an OCT signal demodulation system. On the other sub-optical path of the beam splitter, the OCT refractive compensation lens group, the collimator, the OCT sample arm input fiber connector, and the OCT signal demodulation system are sequentially arranged from near to far. The OCT refractive compensation screw is threadedly connected to the OCT refractive compensation lens group, and the OCT refractive compensation screw is driven by the OCT refractive compensation motor; The described reference arm system includes an OCT reference arm input fiber connector, a reference arm collimator, a reference arm focusing lens, and a reference arm reflector. Behind the OCT signal demodulation system, the OCT reference arm input fiber connector, the reference arm collimator, the reference arm focusing lens, and the reference arm reflector are sequentially arranged. The reference arm focusing lens and the reference arm reflector form a reference surface module. The reference surface module moves along the optical axis direction driven by a screw to change the actual position of the reference surface.

2. An autofocus method for the automated fundus examination device for diabetic retinopathy screening as described in claim 1, characterized in that: It includes the following steps: Step 1, move the reference surface module to scan the actual position of the reference surface once in the entire OCT imaging range to obtain an OCT image corresponding to the reference surface position information; Select the reference surface position corresponding to the strongest signal-to-noise ratio. This reference surface position is the optimal reference surface; Moving the reference surface module to the optimal reference surface position can obtain an OCT image with the best signal-to-noise ratio; Step 2, move the OCT refractive compensation lens group within the designed range, and the focal position of the incident light will move along the optical axis direction accordingly. When the incident light converges at the retina position, the signal-to-noise ratio of the OCT image is the strongest, and the peak position is the corresponding optimal refractive compensation position; Record this optimal refractive compensation position, and the OCT refractive compensation motor drives the OCT refractive compensation lens group to move to this optimal refractive compensation position to complete the OCT automatic refractive compensation; Step 3 Feed the optimal refractive compensation position back to the fundus camera system. The focusing motor of the fundus camera drives the imaging objective lens group and the image receiver of the fundus camera to move together. The corresponding relationship between the focusing position of the fundus camera and the OCT refractive compensation position is positively correlated. Establish a one-to-one correspondence between the focusing position of the fundus camera and the OCT refractive compensation position, or use a screw with a linearly proportional pitch to establish a direct proportional relationship between the focusing position of the fundus camera and the OCT refractive compensation position. Find the corresponding focusing position of the fundus camera through the known OCT refractive compensation position to complete the automatic focusing of the fundus camera image.

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