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This study sought to develop and evaluate infrared thermal imaging technology capable of analyzing the water status of crops in a noncontact and nondestructive manner. An infrared thermal imaging device was employed to obtain thermal images from crops. Additionally, to obtain accurate leaf temperatures, we implemented an infrared thermal imaging process capable of precisely extracting the leaf temperature from a peach tree. Furthermore, leaf temperatures were corrected with regard to experimentally obtained leaf emissivity of the peach tree. Leaf temperature and environmental information were then utilized for the analysis of crop water stress index (CWSI). The CWSI was used to compare and evaluate the water stress levels among four different types of peach trees in soils that were subjected to different irrigation conditions. Leaf temperature and environmental information are utilized in the analysis of CWSI, which successfully indicates the quantitative water status of the subject trees. For the crop subjected to the highest water stress (− 80 kPa), CWSI reached a value of 0.76 before irrigation. After irrigation in the morning of the fourth day, CWSI is notably lower; however, it increases the next day when water stress resumes. For crops exposed to lower water stress (control and − 30 kPa), the CWSI values drop immediately to almost zero upon irrigation; however, their CWSI values also resume increasing on the fifth day. We demonstrate that crop water stress, which happens under conditions of water deficiency, causes an increase in leaf temperature that can be detected via the proposed thermal imaging technique. These results show that time-resolved thermal images of leaf temperatures are meaningfully related to the physiological characteristics of crops that are exposed to water deficits.

A scan driver circuit that generates stable output waveforms with the depletion-mode oxide thin-film transistor (TFT) is reported. The output waveforms of the conventional scan driver deteriorate as the threshold voltage of the TFT becomes negative. For the proper operation of a scan driver circuit composed of oxide TFTs, the TFTs in the circuit should be turned off with negative gate-to-source bias. In addition, the output of each stage should not be affected by the adjacent stages. In this study, a new scan driver circuit that satisfies these two criteria was designed and fabricated. The new scan driver circuit works successfully and exhibits no ripple in the output waveforms even though the threshold voltage of the TFTs is as low as −3 V.

In this paper, a gate driver circuit for In–Ga–Zn–O thin-film transistors (TFTs) driven by only two clock signals is reported. In this circuit, the TFTs are turned off with a negative V GS by the two clock signals. As a result, it works properly and suppresses power consumption increase even though the TFT V T shifts in the negative direction.

A new level shifter circuit suitable for implementation using n-channel oxide thin-film transistors (TFTs) is reported. This level shifter is designed to convert a single 10 V input signal into a 20 V output signal. In order to raise the output voltage up to VDD in spite of the large zero- VGS current of the oxide TFT, negative VGS is applied to the pull-down TFTs. Simulation and fabrication results show that the level shifter operates correctly with oxide TFTs and that the power consumption is as low as 0.2 mW at an input signal frequency of 10 kHz.