| Intracellular free calcium ([Ca2+]i) is one of the most important second messengers in living cells. [Ca2+]i regulates many physiological activities. It is important to research the activity of Ca2+ inside and outside of the cells. Fluorescence microscopy has many advantages, such as high temporal resolution and low toxicity to the cells. So the fluorescence microscopy is an important and significative method to study in living cells.Exploring a new detecting method for intracellular calcium concentration is the main task of this thesis. In the system, pulses with given frequency was used to drive LED to produce ultraviolet, which activates the fluorochrome caged on Ca 2+ to emit fluorescence. Following that the fluorescence signal was transformed to voltage signal by PMT. At the same time, detected out the amplitude of the voltage signal that is just a mirror image of the calcium ion concentration. So the calcium ion concentration was acquired.The content of the thesis can be divided into three parts:The first part concerns in the signal generator including direct digital synthesizing (DDS) chip and MCU (AT89S51) was discussed.In the second part, the concerned detecting principle and its application in this system was introduced, including the method with which transformed the sine wave into pulse,multiplier circuit and phase-shift circuit.In the third part, the way how to choose and design the low pass filter circuit was discussed.And the stimulation of this low pass filter circuit was done with PSpice,the result demonstrated that the direct voltage which is needed by the system can be detected in the specified period.Finally the conclusion and the prospect of the whole thesis was given.
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