Patent ID: 6747695
Filing Date: 2004-06-08
Classification: H04N

Abstract:
An image sensor comprising:a plurality of pixel rows pixel_row(i), i=1,2, . . . , n, wherein each pixel row comprises a plurality of pixel circuits; wherein each pixel circuit cornprises: a pixel diode; a reset switch coupling the pixel diode to a bias voltage circuit so as to reverse bias the pixel diode only if ON; a capacitor; a shutter switch coupling the capacitor to the pixel diode so that a voltage drop across the capacitor is responsive to a voltage drop across the pixel diode only if the shutter switch is ON; a transistor follower connected to the capacitor to provide a voltage signal that follows the voltage drop across the capacitor; and a row select switch coupled to the transistor follower; the sensor further comprising: a plurality of column lines column_line(j), j=1,2, . . . , m, wherein for each i=1,2, . . . , n, for each j=1,2, . . . , m, column_line(j) is connected to pixel circuit pixel_circuit(i,j) belonging to the plurality of pixel circuits within pixel_row(i) via the row select switch of pixel_circuit(i,j), where for each i=1,2, . . . , n, for each j=1,2, . . . , m, pixel_circuit(i,j) is to provide on column_line(j) a calibration voltage signal calibration_voltage(i,j) equal to the voltage signal provided by pixel_circuit(i,j) only if the reset switch, the shutter switch, and row select switch for pixel_circuit(i,j) are ON, and a sample voltage signal sample_voltage(i,j) equal to the voltage signal provided by pixel_circuit(i,j) only if the reset switch and shutter switch for pixel_circuit(i,j) are OFF and the row select switch for pixel_circuit(i,j) is ON; and an opaque layer deposited proximal to the plurality of pixel rows so that for each i=1,2, . . . , n, a set dark_pixel_set(i) of at least one pixel circuit belonging to pixel_row(i) is permanently dark.