Study On Effect Of Machining Errors On Optical Performance In Freeform Optics

Comparing with traditional optics,freeform optics can improve optical performance extremely due to specially designed structures,such as correcting deviation,decreasing image aberrations,enlarging depth of field and so on,thus improving optical quality and evolving to core parts in all kinds of advanced optical systems.The design and application demand of freeform optics have strict requirements on machining accuracy(including surface quality and form accuracy)to achieve precise control over rays with specially designed surface shape.However,freeform optics is a device mainly for practical applications.Depending merely on geometric surface precision can hardly achieve integrated evaluation of the machining quality,and manufacturing of optical freeform surfaces should adapt to the need of applications.Optical imaging quality ought to be ultimate evaluation in the optical machining,such as spherical aberration,coma,dispersion that describe imaging aberration,and distortion,root-mean-square error(RMS),point spread function,optical transfer function(MTF)that are used to evaluate imaging quality overall.To analyze the influence of surface errors caused by ultra-precision machining on optical imaging performance,and then quest what distributive surface error benefits the improvement of imaging quality,realize controllable manufacturing process based on optical imaging quality.This paper conducted relevant studies as the following:1.Surface errors and wavefront aberrations of optical elements were incorporated on specific surfaces with Zernike polynomials based on CODE V interferogram file function.Afterwards,this paper analyzed changes of optical parameter values before and after errors were incorporated to study the influence of machining errors of micro lens array on optical performance,and quest what distributive error benefits the improvement of imaging performance.2.Vector expression of ray tracing was derived,which was used to set up the transformation model between surface errors and wavefront aberrations of paraboloid.Optical path simulations aiming at on-axis and off-axis paraboloid were conducted to validate correctness of the transformation model.3.Off-axis paraboloid array was machined,and wavefront aberrations of unit lens measured by the interferometer were transformed to surface errors.Contrast was made between results of CODE V simulation and interferogram to validate the correctness of proposed research method in this paper.