Research On The Key Technology Of Optical Distance Measurement System Based On Swept Optical Coherence Tomography

With the development of modern technology,whether it is in mobile phones,aerial drones,SLR cameras,or in medical equipment,scientific research applications,aerospace science and technology,national defense,optical systems are playing an increasingly important role.Optical lens spacing information is one of the most important parameters,which directly affects the imaging quality of the system.The traditional distance measurement method is directly through contact measurement,which not only has a large error,but also causes scratches on the mirror surface.So a non-contact high-precision measuring instrument is very important.Optical coherence tomography(OCT)can be well applied in optical system ranging because of its non-invasive,non-contact,high resolution and non-destructive characteristics.With the development of OCT technology,swept source OCT(SS-OCT)has become the third generation of OCT system because of its simple structure,fast speed and high sensitivity.So SS-OCT has a good application potential in the distance measurement of mirror spacing.However,the measurement range of traditional SS-OCT is only a few millimeters,which is obviously not enough.Therefore,this article studies the key technologies of SSOCT in its measurement range.mainly including:For the complex conjugate image that SS-OCT will inevitably produce,this paper incorporates a phase shift method to eliminate the mirror multiplier.In this paper,innovative improvements have been made to the defects of the phase-shift method,mainly from the theoretical derivation to the simulation analysis of the effect of the phaseshift error on the residual image.Therefore,an iterative method is proposed to filter out the phase with less error in the phase of continuous oscillation,so as to obtain the perfect image effect.Finally,the advantages of the algorithm were verified through experiments.The traditional phase-shifting method requires PZT,but the disadvantages of PZT's easy damage and high cost are not conducive to application to instrumented equipment.Because the servo system must be introduced into the system in this paper to change the position of the plane mirror on the reference arm to match different optical path positions,and the servo system often causes resonance,Therefore,this paper innovatively combines the improved algorithm and resonance to perfectly eliminate the image,so that no additional PZT introduction is needed,which greatly reduces the cost and complexity of the instrument.We analyze the torsional vibration caused by two mass servo system and use it as the phase oscillation source.Combined with our algorithm,we have perfectly eliminated the image without using PZT,and doubled it to an ultra-long range of 180 mm.measuring.The performance of the system is tested with a standard gauge block of 135 mm,and the measurement accuracy is better than 650 nm.According to the C + + software of our system,including the control of system hardware,data acquisition,the algorithm of eliminating mirror image,GPU algorithm acceleration,measurement interface,and a semi-automatic automatic measurement method,real-time measurement is realized.