Image sensor and optical signal generation method

An image sensor comprising:

• a pixel array including a plurality of pixels arranged in a matrix,
• each of the pixels including:
• a photodiode configured to operate in one of a linear mode for linearly responding to a light incident amount and a photo-voltaic mode for logarithmically responding to the light incident amount;
• and
• a source follower circuit configured to output a signal voltage according to a signal charge generated according to an output of the photodiode, wherein the source follower circuit further includes a source follower transistor to a gate of which the output of the photodiode is connected and a negative pulse in a period shorter than a half period of one frame is applied to the photodiode via a gate capacitor of the source follower transistor;
• a vertical scan circuit configured to sequentially drive the plurality of pixels while moving in a vertical direction;
• an analog-to-digital converter configured to convert the signal voltage output from the source follower circuit into digital signal data;
• a frame memory configured to store signal data of one frame;
• a signal converter configured to generate, from signal data of a current frame and signal data of a previous frame, an optical signal relating to the light incident amount;
• and
• a horizontal scan circuit configured to sequentially output the optical signals of the pixels in one row.

An optical signal generation method for generating an optical signal relating to a light incident amount of a photodiode that operates in one of a linear mode for linearly responding to a light incident amount and a photo-voltaic mode for logarithmically responding to the light incident amount,

• the optical signal generation method comprising:
• extracting an output of the photodiode frame by frame without resetting an accumulated electric charge of the photodiode;
• and
• generating, based on a signal of a current frame relating to an output in the current frame of the photodiode and a signal of a previous frame relating to an output in an immediately preceding frame of the photodiode, an optical signal relating to the light incident amount in the current frame using a signal converter provided in advance, wherein the signal converter generates the optical signal from the signal of the current frame and the signal of the previous frame using a Lambert W function.

An image sensor comprising:

• a pixel array including a plurality of pixels arranged in a matrix,
• each of the pixels including:
• a photodiode configured to operate in one of a linear mode for linearly responding to a light incident amount and a photo-voltaic mode for logarithmically responding to the light incident amount;
• a source follower circuit configured to output a signal voltage according to a signal charge generated according to an output of the photodiode;
• and
• a capacitor connected to the photodiode, wherein a negative pulse in a period shorter than a half period of one frame is applied to the photodiode via the capacitor;
• a vertical scan circuit configured to sequentially drive the plurality of pixels while moving in a vertical direction;
• an analog-to-digital converter configured to convert the signal voltage output from the source follower circuit into digital signal data;
• a frame memory configured to store signal data of one frame;
• a signal converter configured to generate, from signal data of a current frame and signal data of a previous frame, an optical signal relating to the light incident amount;
• and
• a horizontal scan circuit configured to sequentially output the optical signals of the pixels in one row.