| 摘要 |
PURPOSE:To take a high-accuracy measurement by reducing variation in measured density due to up/down movements of the measurement surface of a sample even if the measurement surface moves up and down slightly. CONSTITUTION:A photosensor and the sample are so arranged in such a position relation that the height from the center 20a of the photosensor to the sample is h0, the angle between the measurement surface 10a of the sample and the photosensor 20 is theta0, and the distance from the center 20a of the photosensor to the optical axis of irradiated light is r0. Then, when the distance r0 and the angle theta0 are set properly, the relation between the height (h) and a sensor output I on the condition of the combination of the distance and angle is an arch curved as shown by an output curve in a figure and the output I of the photosensor 20 has a peak value when the height (h) is specific. For the purpose, the height when the output curve at the time of the distance r0 and angle theta0 is set to h0. Consequently, even when the holding accuracy of the sample varies in height h0 with the size accuracy of the sample itself on every measurement, variation in photosensor output I due to the height variation DELTAh is DELTAI1 and a little as shown in a figure, so that a high-accuracy measurement is taken with a small error in measurement. |
