Thermal And Mechanical Damage Of Optical Lens Irradiated By Pulsed Laser And Its Influence On Imaging

Femtosecond pulse laser is used to irradiate optical lenses to simulate the radiation effect of space energetic particles on spacecraft imaging system.The experimental research and numerical simulation of femtosecond pulse laser irradiating K9 optical lenses are carried out.At the same time,in order to further clarify the influence of laser pulse width,output power,incident angle and pulse frequency on the thermal effect,ablation morphology and imaging of optical lens,the experimental study of millisecond pulsed laser irradiation on K9 optical lens under different irradiation parameters was carried out.The influence of pulse laser irradiation parameters on the thermal effect,ablation morphology and imaging of K9 optical lens was obtained,which provided a theoretical reference for evaluating the service life of optical lens,proposing reinforcement measures and realizing fine processing of laser.The main research contents and results of this paper are as follows :(1)The thermal effect measurement system of optical lens irradiated by laser is constructed.The temperature field and stress evolution process of optical lens irradiated by femtosecond pulse laser are obtained.The relationship function between laser incident angle and irradiation temperature and stress characteristic parameters is determined.The influence of laser incident angle on irradiation temperature is further clarified by numerical simulation.The results show that the temperature and stress(circumferential and radial)in the laser irradiation area increase with the decrease of the laser incident angle.The temperature difference between the target plate near the laser incident direction and the target plate far from the laser incident direction is also increased.When the laser incident angle is less than 45 °,the temperature difference between the irradiation area near the incident laser beam side and the corresponding far side area increases with the decrease of the laser incident angle.When the laser incident angle is greater than 45 °,the temperature evolution trend is opposite.(2)The experimental study on the temperature field and stress-strain evolution characteristics of optical lenses irradiated by millisecond pulsed laser is carried out,and the relationship between laser incident angle and temperature,stress(circumferential and radial)of optical lenses is obtained.The influence of millisecond pulse laser irradiation parameters on the temperature and stress evolution characteristics of optical lenses is clarified.The maximum temperature and stress(circumferential and radial)in the laser irradiation area increase with the decrease of laser incident angle and the increase of laser power.Under the same irradiation conditions,the temperature of coated optical lenses is lower than that of uncoated optical lenses,and the temperature evolution trend is the same.(3)The damage morphology of femtosecond and millisecond pulsed laser ablation optical lenses was observed by microscope.The results show that when the laser source is femtosecond pulse laser,the area of the ablation area increases with the decrease of the incident angle.Because the heat affected zone of femtosecond pulse laser is small,the influence on imaging can be ignored.When the laser source is millisecond pulse laser,with the decrease of incident angle and spot radius and the increase of pulse width,the area of ablation area increases,and the influence on imaging is obvious.It is proved that laser power density and incident angle are the main factors that affect the imaging effect of optical lens.