Fluorescent-Based Temperature Measurement with Simple Compensation of Photo-Degradation Using Hydrogel-Tool and Color Space Conversion

We developed a method to obtain stable and long-lifetime temperature measurements using a fluorescence micromeasurement system. A hydrogel tool containing nano-semiconductor quantum dots (Q-dots) was developed as a fluorescent temperature indicator. We used image processing to convert RGB information to other color information to compensate for photodegradation. The temperature was calibrated using the hydrogel tool in several color spaces, including RGB (R: red, G: green, B: blue), HSV (H: hue, S: saturation, V: value (brightness)), and YCrCb (Y: brightness, Cr: red color difference, Cb: blue color difference). The calibration results showed that R, G, B, Y, and Cr decreased monotonically with increasing temperature, whereas H and Cb did not decrease monotonically. The photodegradation analysis showed that Cr was robust against the brightness fluctuation; however, R, G, and B strongly affected the brightness fluctuation because these values included the brightness information. These results show that temperature measurements based on Cr values are suitable to compensate for photodegradation and have a sensitivity of - 1.3%/K and an accuracy of 0.3 K. These values are the same as those obtained using the fluorescence intensity method.