Image sensor having charge storage regions

Claim 2

An image sensor comprising a plurality of photodiodes (5₁ - 5₄); a plurality of charge storage regions (PWs) for storing charges from the respective photodiodes, the plurality of charge storage regions comprising respective floating electrodes (7₁ - 7₄), potentials of the floating electrodes varying in accordance with amounts of charges stored in the respective charge storage regions (PWs); and charge transferring means (9) for transferring the charges from the plurality of charge storage regions in response to a predetermined transfer clock (0̸1, 0̸2), characterized in that the image sensor comprises a plurality of potential monitoring means (T21 - T24, T31 - T34) connected to the respective floating electrodes (7₁ - 7₄) for separately monitoring changes in potential of the respective floating electrodes; and output means (T25 - T27, R21; T35 - T37, R31) for producing an output signal (Vo(max), Vo(min)) which varies in accordance with one of the monitored potentials which is one of the highest potential and the lowest potential.

Claim 3

An image sensor as claimed in claim 1, characterized in that each of the plurality of potential monitoring means comprises a variable resistor (T21 - T24 , T31 - T34), a resistance of which changes depending on the potential of the corresponding floating electrode (7₁ - 7₄).

Claim 4

An image sensor as claimed in claim 1, characterized in that each of the plurality of potential monitoring means comprises a p-channel metal-oxide-semiconductor (MOS) transistor (T21 - T24), and in that a gate of the p-channel MOS transistor (T21 - T24) is connected to the corresponding floating electrode (7₁ - 7₄), and a drain of which is connected to ground, and a source thereof is connected to sources of p-channel MOS transistors of other potential monitoring means.

Claim 5

An image sensor as claimed in claim 3, characterized in that the output means (T25 - T27, R21) comprises bias means (T25, R21) for biasing the mutually connected sources of the p-channel MOS transistors (T21 - T24) of the potential monitoring means.

Claim 6

An image sensor as claimed in claim 4, characterized in that the bias means comprises one of a resistor (R21) connected to a positive power source (Vc) and a MOS transistor (T25) connected to the positive power source (Vc).

Claim 7

An image sensor as claimed in claim 1, characterized in that the image sensor further comprises preset means (T11 - T14) for setting all the floating electrodes (7₁ - 7₄) at a preset potential (V A ) before sensing light irradiated on the photodiodes (5₁ - 5₄).

Claim 8

An image sensor as claimed in claim 6, characterized in that the preset means (T11 - T14) comprises n-channel MOS transistors (T11 - T14) provided for the respective floating electrodes (7₁ - 7₄), and a drain of each of the n-channel MOS transistors (T11 - T14) is provided with the predetermined power source voltage (V A ), and a source thereof is connected to the corresponding floating electrode (7₁ - 7₄), and a gate thereof is supplied with a preset signal (P) fed from an external circuit.

Claim 9

An image sensor as claimed in claim 4, characterized in that the output means (T25 - T27, R21) comprises voltage division means (T26, T27) for dividing a predetermined power source voltage (V A ) in accordance with a potential of the mutually connected sources of the p-channel MOS transistors (T21 - T24), and a divided voltage is said output signal (Vo(max)).

Claim 10

An image sensor as claimed in claim 4, characterized in that the voltage division means comprises first and second n-channel MOS transistors (T26, T27), and a drain of the first n-channel MOS transistor (T26) is supplied with the predetermined power source voltage (V A ), and a source thereof is connected to a drain of the second n-channel MOS transistor (T27), and a gate of the first n-channel MOS transistor (T26) is connected to the mutually connected sources of the p-channel MOS transistors (T21 - T24) of the potential monitoring means, and in that a source of the second n-channel MOS transistor (T27) is connected to ground, and a gate thereof is provided with a constant bias voltage (V REF1 ).

Claim 11

An image sensor as claimed in claim 1, characterized in that each of the plurality of potential monitoring means comprises an n-channel metal-oxide-semiconductor (MOS) transistor (T31 - T34), and in that a gate of the n-channel MOS transistor (T31 - T34) is connected to the corresponding the floating electrode (7₁ - 7₄), and a drain of which is supplied with a predetermined power source voltage (V A ), and a source thereof is connected to sources of n-channel MOS transistors of other potential monitoring means.

Claim 12

An image sensor as claimed in claim 10, characterized in that the output means (T35 - T37, R31) comprises bias means (T35, R31) for biasing the mutually connected sources of the n-channel MOS transistors (T31 - T34) of the potential monitoring means.

Claim 13

An image sensor as claimed in claim 10, characterized in that the bias means (T35, R31) comprises at least one of a resistor (R31) connected to ground and a MOS transistor (T35) connected to the ground.

Claim 14

An image sensor as claimed in claim 10, characterized in that the output means (T35 - T37, R31) comprises voltage division means (T36, T37) for dividing a predetermined power source voltage (V A ) in accordance with a potential of the mutually connected sources of the n-channel MOS transistors (T31 - T34), and a divided voltage is said output signal (Vo(min)).

Claim 15

An image sensor as claimed in claim 10, characterized in that the voltage division means comprises first and second n-channel MOS transistors (T36, T37), and a drain of the first n-channel MOS transistor (T36) is supplied with the predetermined power source voltage (V A ), and a source thereof is connected to a drain of the second n-channel MOS transistor (T37), and a gate of the first n-channel MOS transistor (T36) is connected to the mutually connected sources of the n-channel MOS transistors (T31 - T34) of the potential monitoring means, and in that a source of the second n-channel MOS transistor (T37) is connected to ground, and a gate thereof is provided with a constant bias voltage (V REF2 ).

Claim 16

An image sensor comprising a plurality of photodiodes (5₁ - 5₄); a plurality of charge storage regions (PWs) for storing charges from the respective photodiodes, the plurality of charge storage regions comprising respective floating electrodes (7₁ - 7₄), potentials of the floating electrodes varying amounts of charges stored in the respective charge storage regions (PWs); and charge transferring means for transferring the charges from the plurality of charge storage regions in response to a predetermined transfer clock (0̸₁, 0̸₂), characterized in that the image sensor comprises a plurality of potential monitoring means (T21 - T24, T31 - T34), connected to the respective floating electrodes (7₁ - 7₄) for separately monitoring changes in potential of the respective floating electrodes; first output means (T26, T27, T49) for producing a first output signal (Vo(max)) which varies in accordance with one of the monitored potentials which is the highest; and second output means (T36, T37, T50) for producing a second output signal (Vo(min)) which varies in accordance with one of the monitored potentials which is the smallest.

Claim 17

An image sensor comprising a plurality of photodiodes (5₁ - 5₄); a plurality of charge storage regions (PWs) for storing charges from the respective photodiodes, the plurality of charge storage regions comprising respective floating electrodes (7₁ - 7₄), potentials of the floating electrodes varying amounts of charges stored in the respective charge storage regions (PWs); and charge transferring means for transferring the charges from the plurality of charge storage regions in response to a predetermined transfer clock (0̸₁, 0̸₂), characterized in that the image sensor comprises a plurality of potential monitoring means (T21 - T24, T31 - T34), connected to the respective floating electrodes (7₁ - 7₄) for separately monitoring changes in potential of the respective floating electrodes; first output means (T26, T27, T49) for producing a first output signal (Vo(max)) which varies in accordance with one of the monitored potentials which is the highest; and second output means (T36, T37, T50) for producing a second output signal (Vo(min)) which varies in accordance with one of the monitored potentials which is the smallest.

Claim 18

An image sensor as claimed in claim 15, characterized in that each of the plurality of the potential monitoring means comprises a first variable resistor (T21 - T24) and a second variable resistor (T31 - T34), and in that the first variable resistor (T21 - T24) decreases its resistance with a decrease in potential of the corresponding floating electrode (7₁ - 7₄), and in that the second variable resistor (T31 - T34) increases its resistance with a decrease in potential of the corresponding floating electrode (7₁ - 7₄).

Claim 19

An image sensor as claimed in claim 16, characterized in that the first variable resistor (T21 - T24) comprises a p-channel MOS transistor (T21 - T24), and the second variable resistor (T31 - T34) comprises an n-channel MOS transistor (T31 - T34).

Claim 20

An image sensor as claimed in claim 16, characterized in that the first variable resistors (T21 - T24) are connected directly to the respective floating electrodes (7₁ - 7₄), and in that the image sensor further comprises a plurality of level shift means (LS1 - LS4) provided for the respective floating electrodes (7₁ - 7₄) for shifting the potential of the respective floating electrodes (7₁ - 7₄) by a predetermined level, and in that level-shifted potentials of the floating electrodes (7₁ - 7₄) are supplied to the respective first variable resistors (T21 - T24).

Claim 21

An image sensor as claimed as claim 18, characterized in that each of the level shift means (LS1 - LS4) comprises a first n-channel MOS transistor (T41, T43, T45, T47) and a second n-channel MOS transistor (T42, T44, T46, T48), and in that gates of the first n-channel MOS transistors (T41, T43, T45, T47) are connected to the respective floating electrodes (7₁ - 7₄), and gates of the second n-channel MOS transistors (T42, T44, T46, T48) are supplied with a constant voltage signal (V BS ), and in that drains of the first n-channel MOS transistors (T41, T43, T45, T47) are supplied with the predetermined power source voltage (V A ), and sources thereof are connected to drains of the corresponding second n-channel MOS transistors (T42, T44, T46, T48), and sources of the second n-channel MOS transistors (T42, T44, T46, T48) are connected to ground.

Claim 22

An image sensor as claimed in claim 15, characterized in that the image sensor further comprises control means (50) for generating a clock signal (C TG ) which determines timing for transferring the charges stored in the charge storage regions (PWs) to the transfer means on the basis of the first and second output signals (Vo(max), Vo(min)) derived from the first and second output means (T26, T27, T50: T36, T37, T49).