In this paper, we propose a new simple device for visualizing bioactive molecules with a fine spatial resolution by using a membrane in which a specific enzyme is immobilized. The layer produces fluorescence after association with a specific substance. The layer, on which a biological tissue is to be mounted, is deposited on a quartz substrate that is used as a light guide to introduce UV light to the layer. Substance release is observed by a CCD camera from the opposite side of the substrate. In order to shorten the experiment time, we had automated the optical device. The paper also describes the reduction of background fluorescence by means of image processing technique. Images were acquired by employing two UV-LEDs with slightly different angle. Image processing was performed to separate background and target fluorescence by means of independent component analysis. Finally the release of GABA(γ-aminobutyric acid) and glutamate from specific layers in rat cerebellum was successfully observed. It is expected that, using this method, both real-time transmitter release and its response to medicine can be observed.