It seems that the sensor requires manually charge and discharge the capacitor inside (see the demonstration part). This cause delay in getting immediate reading, and the reading will be more discrete than that of regular line sensors. I wonder if I use the sensor correctly, or if I fail to exploit the superiority of 555-27401, cauz it sells more expensive.555-27401-QTI-Line-Sensor-Documentation-v1.0 (1).pdf (50.0 KB)
The nature of the sensor mentioned would indeed provide readings at periodic intervals, similar to the way that a camera provides image data at some particular frame rate. This allows adaptation to a wide variety of reflectivity conditions without need for a high-resolution ADC by adjusting exposure times. In trade, the bandwidth of the sensor is reduced.