CMOS image sensor having wide dynamic range and sensing method thereof

A CMOS image sensor including an array of unit pixels, each unit pixel being connected to an output signal line that is arranged in each column of the array, wherein the unit pixel comprises:

• a photodiode;
• a first processing unit connected to the photodiode, that amplifies a first floating diffusion voltage formed by being provided with electrons accumulated in the photodiode during a first exposure integration time and transmits the amplified voltage to the output signal line;
• a second processing unit connected to the photodiode, that amplifies a second floating diffusion voltage formed by being provided with electrons accumulated in the photodiode during a second exposure integration time which is separated from the first exposure integration time and transmits the amplified voltage to the output signal line;
• and
• an erasing transfer gate transistor arranged between the photodiode and a power supply voltage, the erasing transfer gate transistor is kept turned off during both first and second exposure integration times wherein electrons accumulate in the photodiode, otherwise the erasing transfer gate transistor discharges electrons accumulated in the photodiode so as to reset the photodiode;
• wherein the electrons are transferred to and stored in the first floating diffusion before beginning the second exposure integration and then the electrons again accumulate in the photodiode and are transferred to and stored in the second floating diffusion.

A sensing method of a CMOS image sensor including an array of unit pixels, comprising:

• dividing a shuttering section to obtain an image frame into a first exposure integration time and a second exposure integration time;
• performing double shuttering by implementing a procedure to accumulate electrons in a photodiode during the first exposure integration time, transfer and store the electrons in a first floating diffusion and then accumulate electrons accumulated in the photodiode during the second exposure integration time, transfer and store the electrons in a second floating diffusion, the procedure being simultaneously implemented for all pixels of the pixel array;
• performing sampling by reading voltages generated by the electrons stored in the first and second floating diffusions through the double shuttering according to a double sampling method respectively, and transmitting the voltages to output signal lines connected to the unit pixel, corresponding to multiple exposure integrations in parallel;
• and
• sequentially repeating the sampling row by row in the pixel array, the sampling being simultaneously performed with respect to all unit pixels of each row.

A sensing method of a CMOS image sensor including an array of unit pixels, comprising:

• dividing a shuttering section to obtain an image frame into a first exposure integration time and a second exposure integration time;
• performing a double shuttering by accumulating electrons in a photodiode during a first exposure integration time, transferring and storing the electrons in the first floating diffusion, and then accumulating electrons in the photodiode during a second exposure integration time;
• performing sampling by reading a voltage generated by the electrons stored in the first floating diffusion according to a double sampling method, reading a voltage generated by the electrons which are accumulated in the photodiode during the second exposure integration time and transferred into the second floating diffusion according to a correlated double sampling method and transmitting the voltages to output signal lines connected to the unit pixel, corresponding to multiple exposure integrations in parallel;
• and
• sequentially repeating the double shuttering and the sampling connected continuously row by row in the unit pixel array.