A safety syringe has a hollow barrel, a plunger, a connector, a plug and a needle hub. Data obtained by the sensing device can be used in a feedback loop in the apparatus employing the device, to help control the operation of the apparatus in order to obtain consistent results. As this space, it is preferable to use the space on the outer-periphery side of the electric field relaxation member 21 provided inside the porcelain tube 15. The processor detects edges from a plurality of side images of the object with respect to the ROI image. The information display device and the information processor are also capable of changing parameters of the image processing in accordance with a user image preference and an image texture input by the user. Where necessary to maintain a predetermined orientation of the display bar, the display bar can be formed with an axially limited portion of reduced cross section, enabling the mounting brackets, when positioned thereat, to be rotationally reoriented relative to the display bar.