sheet is scanned by the stimulating light. In the point-scan system, reading conditions of the optical system from the stimulable phosphor sheet to the photoelectric transducer device are essentially the same in the main direction and the auxiliary direction. Therefore, if the light is emitted from the stimulable phosphor sheet isotropically in the main and auxiliary directions, an image signal produced by photoelectrically converting the light emitted from the stimulable phosphor sheet has substantially equal spatial frequency characteristics in the main and auxiliary directions, and the sharpness of the image is also substantially the same in the main and auxiliary directions.
Another type of a radiation image information recording and reading system is known as a line-scan system. In the line-scan system, the radiation image information recorded on astimulable phosphor sheet is read by a sensor comprising an array of photoelectric transducers in a main direction while the sensor is moving in an auxiliary direction perpendicular to the main direction. In the line-scan system, since reading conditions differ in the main and auxiliary directions, the spatial frequency characteristics of an image signal produced by photoelectrically converting the light emitted from the stimulable phosphor sheet are generally not equal in the main and auxiliary directions. The spatial frequency characteristics of the image signal in the main direction depend on the focusing capability in the main direction of a light-converging optical system for guiding the light emitted from the stimulable phosphor sheet to the line sensor, and the spacing of the photoelectric transducers of the line sensor in