Abstract: This paper describes a system in which image of biological specimen is obtained from its ESR signal. In order to reduce microwave electric heating in biological specimen effectively and obtain the imaging information of specimen conveniently, the microwave frequency in the system is arranged at L-band and the cavity resonator is replaced by an one-turn plane coil. In this system the magnetic field scanning is controlled and the data collection of ESR signal is completed synchronously by IBM-PC computer. The ability of measurement on weak signal with noise is increased by repeating scanning, collection data, add and average. Finally, the image of specimen is obtained by reconstruction method of convolution filtering back-projection. This system also has the unexpensive feature and it is easy to build.

Key words: ESR, Imaging system, Biological specimen, Image reconstruction