An image sensor has light receiving elements, switching elements for reading out output signals from the light receiving elements, a scanning circuit array for driving the switching elements, and a common signal line connected to the switching elements for transmitting the output signals from the light receiving elements. An operational amplifier is connected to the common signal line through a chip selection switch and is operated by a single power supply under the GND power supply standard common to the image sensor for outputting the output signals to an image signal output terminal. A reset switch is connected to the common signal line for supplying a reference voltage to the common signal line. The reset switch and the switching elements turn ON to reset the light receiving elements to the reference voltage after reading out the output signals from the light receiving elements to the common signal line.
1. An image sensor comprising: a light receiving element circuit array comprised of a plurality of light receiving elements for outputting output signals based on light reception amounts; a switching element circuit array comprised of a plurality of switching elements for reading out the output signals from the light receiving elements; a scanning circuit array for driving the switching elements of the switching element circuit array; a common signal line connected to the plurality of switching elements for transmitting the output signals from the light receiving elements; an operational amplifier connected to the common signal line through a chip selection switch and operated by a single power supply under the GND power supply standard common to the image sensor for outputting the output signals to an image signal output terminal; and a reset switch connected to the common signal line; for supplying a reference voltage to the common signal line; wherein the reset switch and the switching elements turn ON to reset the light receiving elements to the reference voltage after reading out the output signals from the light receiving elements to the common signal line.
2. An image sensor according to claim 1 ; wherein the reset switch is disposed between a reference voltage terminal and the chip selection switch.
3. An image sensor according to claim 1 ; further comprising a reference voltage terminal and a reference voltage generating circuit for supplying the reference voltage to the reference voltage terminal through a resistor.
4. An image sensor according to claim 1 ; further comprising a plurality of unit blocks each having at least the light receiving element circuit array, the switching element circuit array, the scanning circuit array, the common signal line, the reset switch, the image signal output terminal, and the reference voltage terminal, the reference voltage terminals of the unit blocks being connected to one another.
5. An image sensor according to claim 4 ; wherein the unit blocks comprise integrated circuits arranged in series.
6. An image sensor according to claim 4 ; further comprising a capacitance formed between the reference voltage terminals and a ground potential.
7. An image sensor according to claim 4 ; further comprising a capacitance formed between the reference voltage terminals and a power source potential.
8. An image sensor according to claim 5 ; further comprising means for supplying a reference voltage to the reference voltage terminals from outside of the integrated circuits.