Nanosecond-time-response temperature measurements using radiation thermometry during 193 nm and 247 nm pulsed light irradiation: Comparison of corneal surface temperature histories

We have developed the fast time-response measurement of thermal radiation with 15ns rise time to monitor the corneal surface temperature during ArF excimer laser ablation. In this study, we aim to investigate the influence of the relation between the corneal penetration depth and sampling depth of the measurement system on the measured temperature using 193 nm and 247 nm pulsed lights which have different penetration depths of cornea. When the sampling depth was defined as the penetration depth of cornea at the thermal radiation wavelength, we obtained about 3 μm of the sampling depth by pulsed photothermal radiometry (PPTR). In the case of the 247 nm light irradiation, where the corneal absorption coefficient at 247nm was approximately equal to that for the thermal radiation, we found that the measured temperature rises were same as the estimated temperature rises based on the photothermal process. In contrast, in the case of the 193 nm light irradiation, where the absorption coefficient at 193 nm was larger than that for the thermal radiation, we found that the measured temperature rises were lower than the estimated temperature rises.