Japan Society of Ultrasonics in Medicine

Abstract A method of measuring moving characteristics of precision mechanical‐translation stages using ultrasonic plane waves is presented. The moving characteristics are obtained by analyzing the phase variation of ultrasonic waves reflected from a reflector set on the translation stage. The resolution is 4 nm at an ultrasonic frequency of 225 MHz; higher resolution is expected at higher frequencies. The method is demonstrated for a line‐focus‐beam (LFB) acoustic microscopy system. Measurement errors of the phase velocity of leaky surface acoustic waves, caused by the positioning errors of thez‐stage, are investigated both theoretically and experimentally. The linear positioning and straightness errors of thez‐stage are estimated at 225 MHz and these effects on velocity measurements are successfully removed using the measured moving characteristics.

Abstract One of the causes of the image‐quality degradation in emission computed‐tomography (ECT) is the characteristic of the aperture of its detection system. This is due to the geometrical structure of the collimator used for limiting the direction of the emitting ray. This kind of degrading causes a shift‐variant blurring in its reconstructed image. We have proposed a method of compensating the degradation by expanding the measured projection data into their frequency space so that the effect of the aperture is turned into a shift‐invariant blurring in each frequency [4, 5], This paper describes an application of the correction method to actual data obtained by light‐emission CT using visible light. The result confirms the usefulness of the proposed method.