| The femtosecond laser bio-tissue cutting technology guided by image information provides a new type of high-precision automation solution for ophthalmic clinical surgery,and has become the latest technology for ophthalmic surgery such as cataract.The key to femtosecond laser cataract surgery is to obtain spatial position information of the surgical trajectory,and then guide the femtosecond laser to perform continuous single-point cutting on the specified position of the eye according to the planned trajectory.Optical coherence tomography(OCT)is a key device for the diagnosis of current eye diseases.It has the characteristics of fast imaging speed,no contact,non-invasive,no radiation and high resolution.High-resolution imaging of the anterior segment of the eye(including the cornea,iris,lens)and retina of the fundus has been achieved.The cross-sectional imaging can obtain the depth direction data of the operation and become an important tool for surgical navigation.In order to realize the navigation needs of cataract surgery,this paper designed a set of SS-OCT(Sweep Source Optical Coherence Tomography)system with a center wavelength of 1310nm,and completed different modes of imaging and parameter acquisition of the designated surgical site in cataract surgery.The main research contents are as follows:Firstly,the Michelson interferometer is used as a model.An OCT hardware experimental platform consisting of a sample arm module,a reference arm module,a scanning module,a swept source module and a data acquisition module is built.Secondly,the system real-time imaging software was developed based on the Lab VIEW platform.Synchronous control of data acquisition and galvanometer scanning is realized,corresponding imaging modes are designed for different surgical steps,and the data processing process from interference spectral signal to sample tomography is completed.The experimental results show that the imaging rate of this system is 21ms/frame,the vertical resolution is 13.23?m,the lateral resolution is 24.6?m,and the imaging depth in air can reach 17.25mm.Again,the imaging distortion problem is caused by the refraction of the sample during OCT image reconstruction.In this paper,the ray tracing method is used to fit the image contour to obtain the actual depth parameter information of the sample.For the semi-annular glass sample experiment of standard structure,the structural parameters of the sample before and after image distortion correction were compared to verify the effectiveness of the method.Finally,for conventional OCT equipment,a full range of scanned samples is required,and 3D reconstruction can cause problems with increased time.In this paper,by adding a dichroic mirror and a CMOS imaging unit to the sample arm,the matching between the OCT imaging coordinate system and the camera image coordinate system is completed,and the imaging requirement at the specified surgical position is realized.The specific scanning mode imaging experiment at the specified position of the regular shape sample is compared,and the error between the theoretical value and the actual obtained value is compared,and the feasibility of the method is verified. |
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