Infrared sensor, infrared camera, method of driving infrared sensor, and method of driving infrared camera

• US 7,361,899 B2
• Filed: 09/18/2006
• Issued: 04/22/2008
• Est. Priority Date: 12/27/2005
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Iida, Yoshinori
• Primary Examiner(s): Nguyen; Kimberly D.
• Assistant Examiner(s): Kim; Kiho
• Application Number:
  US11/532,771
• Publication Number:
  US 20070145274A1
• Time in Patent Office: 582 Days
• Field of Search: 250/338.1, 250/338.2, 250/338.3, 250/338.4, 250/338.5, 250/339.01, 250/339.02, 250/339.03, 250/339.04, 250/339.05, 250/339.06, 250/339.07, 250/339.08, 250/339.09, 250/339.1, 250/339.11, 250/339.12, 250/339.13, 250/339.14, 250/339.15, 250/341.1, 250/341.2, 250/341.3, 250/341.5, 250/341.6, 250/341.7, 250/341.8, 250/342, 250/343, 250/344, 250/345, 250/346, 250/347, 250/348, 250/349, 250/350, 250/351, 250/352, 250/353, 250/354.1, 250/341.4
• US Class Current: 250/338.4
• CPC Class Codes: G01J 1/46 using a capacitor
• CPC Class Codes: G01J 5/24 Use of specially adapted circuits, e.g. bridge circuits
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H04N 23/20 for generating image signals from infrared radiation only
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20

Abstract

An infrared sensor includes an imaging area including infrared detection pixels; row selection lines; a signal line; a row selection circuit generating a column voltage in the signal line; a column amplifier including a first amplifying transistor which generates an amplification voltage obtained by amplifying the column voltage and a first clamp circuit which holds threshold voltage information of the first amplifying transistor in its gate; a removing circuit including a second amplifying transistor and a second clamp circuit which holds threshold voltage information of the second amplifying transistor in its gate, the removing circuit being connected to the column amplifier to remove a bias component from the amplification voltage; and a reading circuit reading an output voltage from the column amplifier, the output voltage is obtained by excluding at least the bias component from the amplification voltage.

Claims

1. An infrared sensor comprising:

an imaging area disposed on a semiconductor substrate and including a plurality of infrared detection pixels which detect infrared rays;

row selection lines connected to the infrared detection pixels disposed in a row direction;

a signal line connected to the infrared detection pixels disposed in a column direction;

a constant current source connected to the signal line;

a row selection ciruit applying a voltage to the infrared detection pixels via the row selection line and generating a column voltage in the signal line;

a column amplifier connected to the signal line, the column amplifier including a first amplifying transistor which generates an amplification voltage obtained by amplifying the column voltage and a first clamp ciruit which holds threshold voltage information of the first amplifying transistor in a gate of the first amplifying transistor;

a removing ciruit including a second amplifying transistor which has conductivity opposite to that of the first amplifying transistor and a second clamp ciruit which holds threshold voltage information of the second amplifying transistor in a gate of the second amplifying transistor, the removing ciruit being connected to the column amplifier to remove a bias component generated by a bias current, which flows through the column amplifier, from the amplification voltage; and

a reading ciruit reading an output voltage from the column amplifier, the output voltage being obtained by excluding at least the bias component from the amplification voltage.

2. The infrared sensor according to claim 1, wherein

the column amplifier includes

a first node connected to a drain of the first amplifying transistor,

a second node connected to a gate of the first amplifying transistor,

a first coupling capacitor coupled between the second node and the signal line and transmitting the column voltage to a gate of the first amplifying transistor,

a reset transistor connected to the first node and resetting a potential of the first node to a reset voltage, and

a first storage capacitor connected to the first node and storing a first charge which flows through the first amplifying transistor,

the removing ciruit includes

a control voltage input supplying a control voltage,

a third node connected to a drain of the second amplifying transistor,

a fourth node connected to a gate of the second amplifying transistor,

an isolation switch isolating between the third node and the first node during a clamp operation and connecting between the third node and the first node during a period other than the clamp operation period,

a second coupling capacitor connected to between the control voltage input and the fourth node and transmitting the control voltage to a gate of the second amplifying transistor, and

a second storage capacitor connected to the third node and storing a second charge having reverse polarity to that of the first charge, the second storage capacitor storing the second charge based on the control voltage amplified by the second amplifying transistor, and

the removing ciruit cancels the first charge with the second charge through the isolating switch.

3. The infrared sensor according to claim 2, wherein

the imaging area includes at least one optical non-sensitivity pixel column, and

the infrared sensor further comprises a control voltage generator generating the control voltage based on a signal voltage from the optical non-sensitivity pixel string.

4. The infrared sensor according to claim 2, wherein

the column amplifier comprises a third clamp ciruit connected to the first node via the first storage capacitor and outputting the output voltage obtained by subtracting reset noise attributable to the first coupling capacitor and to the second capacitor from the amplification voltage.

5. The infrared sensor according to claim 4, wherein

the third clamp ciruit comprises:

a fifth node connected to one electrode of the first storage capacitor;

a third clamp ciruit connected to the fifth node and clamping the fifth node at a clamp voltage;

a third storage capacitor connected to the fifth node; and

a buffer ciruit connected to between the fifth node and the reading ciruit and outputting a voltage of the fifth node to the reading ciruit.

6. The infrared sensor according to claim 4, wherein

the imaging area includes at least two rows constituted by thermal non-sensitivity pixels.

7. The infrared sensor according to claim 2, wherein

the isolation transistor is set to an off state when the first clamp ciruit and the second clamp ciruit are set to an on state,

the isolation transistor is set to an on state when the first clamp ciruit and the second clamp ciruit are set to an off state.

8. The infrared sensor according to claim 1, wherein

a mutual conductance of the first amplifying transistor is equal to a mutual conductance of the second amplifying transistor.

9. The infrared sensor according to claim 1, wherein

the imaging area includes a row constituted by thermal non-sensitivity pixels.

10. The infrared sensor according to claim 1, wherein

pulse signals are applied to a source of the first amplifying transistor and to a source of the second amplifying transistor.

11. The infrared sensor according to claim 10, wherein

|Vdc−

Vsc|<

|Vda−

Vsa|

where Vsc represents a source voltage of the first amplifying transistor during a clamp operation carried out by the first clamp ciruit, Vdc represents a source voltage of the second amplifying transistor during a clamp operation carried out by the first clamp ciruit, Vsa represents a source voltage of the first amplifying transistor during an amplification operation carried out by the column amplifier, and Vda represents a source voltage of the second amplifying transistor during an amplification operation carried out by the column amplifier.

12. A driving method of an infrared sensor, the infrared sensor comprising an imaging area disposed on a semiconductor substrate and including a plurality of infrared detection pixels which detect infrared rays, row selection lines connected to the infrared detection pixels disposed in a row direction, a signal line connected to the infrared detection pixels disposed in a column direction, a constant current source connected to the signal line, a row selection circuit connected to the row selection lines, a column amplifier connected to the signal line, a removing circuit connected to the column amplifier, and a reading circuit connected to an output of the column amplifier,

the method comprising:

applying a voltage to the infrared detection pixels via the row selection line by using the row selection circuit, thereby generating a column voltage;

generating the amplification voltage obtained by amplifying the column voltage in the column amplifier;

removing a bias component, which is generated by a bias current flowing through the column amplifier, from the amplification voltage by using the removing circuit,

wherein the removing circuit includes a second amplifying transistor which has conductivity opposite to that first amplifying transistor and a clamp circuit which holds threshold voltage information of the second amplifying transistor in a gate of the second amplifying transistor, the removing circuit being connected to the column amplifier to remove a bias component generated by a bias currently, which flows through the column amplifier, from an amplification voltage; and

outputting the output voltage, which is obtained by removing the bias component from the amplification voltage, from the column amplifier to the reading circuit.

13. The method according to claim 12, wherein

the column amplifier includes a first amplifier transistor amplifying the column voltage, a first node connected to a drain of the first amplifier transistor, a second node connected to a gate of the first amplifier transistor, a first coupling capacitor coupled between the second node and the signal line, a first clamp ciruit connected to between the first node and the second node, a first storage capacitor connected to the first node, and a reset transistor connected to the first node,

the method further comprising:

setting the isolation switch to an on state to connect electrically between the first node and the third node;

resetting a potential of the first node and a potential of the third node to a reset voltage by using the reset transistor;

setting the isolation switch to an off state;

connecting electrically between the first node and the second node by using the first clamp circuit, and connecting electrically the third node and the fourth node by using the second clamp ciruit to clamp the second node and the fourth node at a voltage including threshold value information of the first and the second transistors, respectively;

setting the first clamp ciruit and the second clamp ciruit to an off state, and setting the isolation switch to an on state;

inputting the column voltage via the first coupling capacitor to the first amplifying transistor to generate an amplification voltage by amplifying the column voltage;

inputting a control voltage from the control voltage input to the second amplifying transistor to generate a voltage equal to the bias component;

storing a first charge based on the amplification voltage in the first storage capacitor, and storing a second charge, which has reverse polarity to that of the first charge, by a quantity based on the bias component in the second storage capacitor to extinguish a quantity of the first charge corresponding to the bias component with the second charge through the isolation switch; and

outputting a voltage of the first node as the output voltage.

14. The method according to claim 13, wherein

the isolation switch is in an off state during a period of clamp operation of the second node and the fourth node, and the isolation switch is in an on state during a period other than the clamp operation period.

15. The method according to claim 13, wherein

|Vdc−

Vsc|<

|Vda−

Vsa|

where Vsc represents a source voltage of the first amplifying transistor during a clamp operation carried out by the first clamp ciruit, Vdc represents a source voltage of the second amplifying transistor during a clamp operation carried out by the first clamp ciruit, Vsa represents a source voltage of the first amplifying transistor during an amplification operation carried out by the column amplifier, and Vda represents a source voltage of the second amplifying transistor during an amplification operation carried out by the column amplifier.

16. The method according to claim 13, wherein

at least one thermal non-sensitivity pixel row is disposed in the imaging area, and the clamp operation of the second node and the fourth node is executed during a period while the thermal non-sensitivity pixel row is selected.

17. The method according to claim 12, wherein

the imaging area includes a thermal non-sensitivity pixel row,

the column amplifier includes a first amplifier transistor amplifying the column voltage, a first node connected to a drain of the first amplifier transistor, a second node connected to a gate of the first amplifier transistor, a first coupling capacitor coupled between the second node and the signal line, a first clamp ciruit connected to between the first node and the second node, a first storage capacitor connected to the first node, a reset transistor connected to the first node, and a third clamp ciruit connected to the first node via the first storage capacitor,

the method further comprising:

the removing ciruit includes a second amplifier transistor having conductivity opposite to that of the first amplifier transistor, a third node connected to a drain of the second amplifying transistor, a fourth node connected to a gate of the second amplifying transistor, a second coupling capacitor coupled between the fourth node and a control voltage input which controls a gate voltage of the second amplifying transistor, a second clamp ciruit connected to between the third node and the fourth node, a second storage capacitor connected to the third node, and an isolation switch connected to between the third node and the first node;

setting the isolation switch to an on state to connect electrically between the first node and the third node;

resetting a potential of the first node and a potential of the third node to a reset voltage by the reset transistor;

setting the isolation switch to an off state during a period while the thermal non-sensitivity pixel row is selected;

connecting electrically between the first node and the second node by using the first clamp ciruit and connecting electrically between the third node and the fourth node by using the second clamp ciruit to clamp the second node and the fourth node at a voltage including threshold value information of the first and the second transistors, respectively;

setting the first clamp ciruit and the second clamp ciruit to an off state, and setting the isolation switch to an on state;

during a period while the thermal non-sensitivity pixel row is selected again;

inputting the column voltage from the thermal non-sensitivity pixel row to the first amplifying transistor via the first coupling capacitor to generate an amplification voltage by amplifying the column voltage;

inputting a control voltage from the control voltage input to the second amplifying transistor to generate a voltage equal to the bias component;

storing a first charge based on the amplification voltage in the first storage capacitor, and storing a second charge, which has reverse polarity to that of the first charge, by a quantity based on the bias component in the second storage capacitor to extinguish a quantity of the first charge corresponding to at least the bias component with the second charge through the isolation switch;

removing reset noise, which is attributable to the first coupling capacitor and the second coupling capacitor, from the amplification noise by using the third clamp circuit;

and

outputting the amplification voltage as the output voltage from the column amplifier after removing the reset noise.

18. The method according to claim 17, wherein

the third clamp circuit includes a fifth node connected to one electrode of the first storage capacitor, a third clamp circuit connected to the fifth node, a third storage capacitor connected to the fifth node, and a buffer circuit connected to between the fifth node and the reading circuit,

the method further comprising:

resetting a potential of the first node to a reset voltage by the reset transistor, after clamp operation of the second node and amplification operation of the first amplifying transistor;

clamping the fifth node at a clamp voltage by setting the third clamp to an on state and inputting the column voltage from the thermal non-sensitivity pixel to the first amplifying transistor via the first coupling capacitor to generate an amplification voltage obtained by amplifying the column voltage;

setting the fifth node to a clamp voltage in a state that a voltage including the reset noise is held in the first node;

setting the third clamp circuit to an off state;

resetting a potential of the first node to the reset voltage of by the reset transistor;

inputting the column voltage from the infrared detection pixels to the first amplifying transistor via the first coupling capacitor to generate an amplification voltage by amplifying the column voltage;

generating an infrared signal component, which is obtained by subtracting a voltage corresponding the reset noise from the amplification voltage, at the fifth node; and

outputting a voltage of the fifth node from the buffer circuit to the reading circuit.

19. The method according to claim 18, wherein

the operation of holding a voltage including the reset noise in the first storage capacitor is executed for each frame.

20. The method according to claim 19,wherein

|Vdc−

Vsc|<

|Vda−

Vsa|

where Vsc represents a source voltage of the first amplifying transistor during a clamp operation at the first node, Vdc represents a source voltage of the second amplifying transistor during a clamp operation at the first node, Vsa represents a source voltage of the first amplifying transistor during an amplification operation at the fifth node, and Vda represents a source voltage of the second amplifying transistor during an amplification operation at the fifth node.

21. An infrared camera comprising:

an imaging area disposed on a semiconductor substrate and including a plurality of infrared detection pixels which detect infrared rays;

row selection line connected to the infrared detection pixels disposed in a row direction;

a signal line connected to the infrared detection pixels disposed in a column direction;

a constant current source connected to the signal line;

a row selection circuit applying a voltage to the infrared detection pixels via the row selection line and generating a column voltage in the signal line;

a column amplifier connected to the signal line, the column amplifier including a first amplifying transistor which generates an amplification voltage obtained by amplifying the column voltage and a first clamp circuit which holds threshold voltage information of the first amplifying transistor in a gate of the first amplifying transistor;

a removing circuit including a second amplifying transistor which has conductivity opposite to that of the first amplifying transistor and a second clamp circuit which holds threshold voltage information of the second amplifying transistor in a gate of the second amplifying transistor, the removing circuit being connected to the column amplifier to remove a bias component generated by a bias current, which flows through the column amplifier, from the amplification voltage; and

a reading ciruit reading an output voltage from the column amplifier, the output voltage being obtained by excluding at least the bias component from the amplification voltage.

22. A driving method of an infrared camera, the infrared sensor comprising an imaging area disposed on a semiconductor substrate and including a plurality of infrared detection pixels which detect infrared rays, row selection lines connected to the infrared detection pixels disposed in a row direction, a signal line connected to the infrared detection pixels disposed in a column direction, a constant current source connected to the signal line, a row selection grit connected to the row selection lines, a column amplifier connected to the signal line, a removing grit connected to the column amplifier, and a reading grit connected to an output of the column amplifier,

the method comprising:

applying a voltage to the infrared detection pixels via the row selection line by using the row selection grit, thereby generating a column voltage;

generating the amplification voltage obtained by amplifying the column voltage in the column amplifier;

removing a bias component, which is generated by a bias current flowing through the column amplifier, from the amplification voltage by using the removing circuit,

wherein the removing ciruit includes a second transistor which has conductivity opposite to that first amplifying transistor and a clamp ciruit which holds threshold voltage information of the second amplifying transistor in a gate of the second amplifying transistor, the removing ciruit being connected to the column amplifier to remove a bias component generated by a bias currently, which flows through the column amplifier, from an amplification voltage; and

outputting the output voltage, which is obtained by removing the bias component from the amplification voltage, from the column amplifier to the reading ciruit; and

reading the output voltage from the column amplifier in the reading ciruit.