Device for detecting defects in solid-state image sensor

An imaging system that is operative in a normal mode and a defect detection mode, comprising:

• a solid-state image sensor having an image pickup area larger than an effective image pickup area;
• a timing generator for producing first and second read pulses for reading out signal charges of first and second fields respectively from photo sensing elements disposed in the pixels of said solid-state image sensor;
• control means for controlling the timing of the production of the first and second read pulses from said timing generator;
• means for detecting a defect comprising means for determining address data of any defective pixel in said solid-state image sensor, and memory means for storing the address data,
• said means for detecting a defect being supplied during a defect detection period with the signal charges of the first and second fields stored for a predetermined number of field periods in said solid-state image sensor and the means for detecting a defect detecting any defective pixel of said solid-state image sensor by detecting the level of the signal charge in each pixel;
• and
• means for correcting a defective pixel by reading out and comparing the signal charge of each pixel with a detection reference level wherein a defective pixel is corrected in response to a defect correction pulse supplied from said means for correcting;
• wherein when said imaging system is operating in said normal mode first read pulses and second read pulses are supplied to said image sensor at a predetermined periodic rate, and when said imaging system is operating in said defect detection mode read pulses are supplied to said image sensor such that a first read pulse is supplied from said timing generator to said solid-state image sensor for reading out and starting storage of the first-field signal charges for a first predetermined number of field periods and a second read pulse is supplied from said timing generator to said solid-state image sensor after a lapse of two fields from the start of the storage of the first-field signal charge for reading out and starting storage of the second-field signal charges for a second predetermined number of field periods.

A method for detecting defects in an imaging system that is operative in a normal mode and a defect detection mode and which includes a solid-state image sensor having an image pickup area larger than an effective image pickup area, comprising the steps of:

• producing first and second read pulses for reading out signal charges of first and second fields, respectively, from photo sensing elements disposed in the pixels of said solid-state image sensor;
• storing signal charges of said first and second fields for a predetermined number of field periods in said solid-state image sensor;
• detecting during a defect detection period the level of the signal charge in each pixel and comparing said level of the signal charge with a detection reference level;
• when said imaging system is operating in said normal mode, supplying first read pulses and second read pulses to said image sensor at a predetermined periodic rate;
• and
• when said imaging system is operating in said defect detection mode supplying read pulses to said image sensor such that a first read pulse is supplied from said timing generator to said solid-state image sensor for reading out and starting storage of the first-field signal charges for a first predetermined number of field periods and a second read pulse is supplied from said timing generator to said solid-state image sensor after a lapse of two fields from the start of the storage of the first-field signal charge for reading out and starting storage of the second-field signal charges for a second predetermined number of field periods.