Distance measurement device and distance measurement system

1. A semiconductor device comprising:

a first photosensor comprising a first light-receiving element, a first transistor, and a second transistor,

wherein a first electrode of the first light-receiving element is directly connected to a first terminal of the first transistor and a first terminal of the second transistor, and

wherein a gate electrode of the first transistor is directly connected to a second terminal of the second transistor.

2. The semiconductor device according to claim 1 ,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor.

3. The semiconductor device according to claim 1 ,

wherein the first photosensor comprises a third transistor, and

wherein a first terminal of the third transistor is electrically connected to the gate electrode of the first transistor and the second terminal of the second transistor.

4. The semiconductor device according to claim 1 ,

wherein the first photosensor comprises a fourth transistor, and

wherein a gate electrode of the fourth transistor is electrically connected to the gate electrode of the first transistor and the second terminal of the second transistor.

5. The semiconductor device according to claim 1 ,

wherein the first photosensor comprises a third transistor and a fourth transistor,

wherein a first terminal of the third transistor is electrically connected to the gate electrode of the first transistor and the second terminal of the second transistor, and

wherein a gate electrode of the fourth transistor is electrically connected to the gate electrode of the first transistor and the second terminal of the second transistor.

6. The semiconductor device according to claim 5 ,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor,

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the third transistor comprises a channel formation region comprising an oxide semiconductor.

7. The semiconductor device according to claim 1 ,

wherein the first photosensor is configured to perform a reset operation by supplying a signal to a second electrode of the first light-receiving element from a first time to a second time,

wherein a light source is configured to perform an irradiation of light to an object from the second time to a fourth time,

wherein the first photosensor is configured to perform a detection of the light reflected off the object from the second time to the fourth time,

wherein the light source is configured to perform the irradiation n times,

wherein the first photosensor is configured to perform the detection n times,

wherein a distance x from the semiconductor device to the object is obtained by:

x

=

c

2

×

(

T

-

S

⁢

⁢

1

n

×

k

)

wherein S1 is a detection signal corresponding to the amount of charge generated by the first light-receiving element in the detection,

wherein T is a time length from the second time to the fourth time,

wherein n is a natural number of 2 or more,

wherein c is light speed, and

wherein k is a constant.

8. The semiconductor device according to claim 1 ,

wherein a light source is configured to perform an irradiation of light to an object from a first time to a fourth time,

wherein the first photosensor is configured to perform a reset operation by supplying a signal to a second electrode of the first light-receiving element from a third time to the fourth time,

wherein the first photosensor is configured to perform a detection of the light reflected off the object from the fourth time to a sixth time,

wherein the light source is configured to perform the irradiation n times,

wherein the first photosensor is configured to perform the detection n times,

wherein a distance x from the semiconductor device and the object is obtained by:

x

=

c

×

S

⁢

⁢

2

2

×

n

×

k

wherein S2 is a detection signal corresponding to the amount of charge generated by the first light-receiving element in the detection,

wherein n is a natural number of 2 or more,

wherein c is light speed, and

wherein k is a constant.

9. The semiconductor device according to claim 1 ,

wherein the first photosensor is configured to perform a first reset operation by supplying a signal to a second electrode of the first light-receiving element from a first time to a second time,

wherein a light source is configured to perform a first irradiation of first light to an object from the second time to a fourth time,

wherein the first photosensor is configured to perform a first detection of the first light reflected off the object from the second time to the fourth time,

wherein the light source is configured to perform a second irradiation of second light to the object from a twelfth time to a fifteenth time,

wherein the first photosensor is configured to perform a second reset operation by supplying the signal to the second electrode of the first light-receiving element from a fourteenth time to the fifteenth time,

wherein the first photosensor is configured to perform a second detection of the second light reflected off the object from the fifteenth time to a seventeenth time,

wherein the light source is configured to perform the first irradiation n times,

wherein the light source is configured to perform the second irradiation n times,

wherein the first photosensor is configured to perform the first detection n times,

wherein the first photosensor is configured to perform the second detection n times,

wherein a distance x from the semiconductor device to the object is obtained by:

x

=

c

×

T

×

S

⁢

⁢

2

2

×

(

S

⁢

⁢

1

+

S

⁢

⁢

2

)

wherein S1 is a detection signal corresponding to the amount of charge generated by the first light-receiving element in the first detection,

wherein S2 is a detection signal corresponding to the amount of charge generated by the first light-receiving element in the second detection,

wherein T is a time length from the second time to the fourth time, and

wherein c is light speed.

10. The semiconductor device according to claim 1 , further comprising:

a second photosensor adjacent to the first photosensor, the second photosensor comprising a second light-receiving element, a fourth transistor, a fifth transistor, and a sixth transistor; and

a power supply line,

wherein a first electrode of the second light-receiving element is electrically connected to a first terminal of the fourth transistor and a first terminal of the fifth transistor,

wherein a gate electrode of the fourth transistor is electrically connected to a second terminal of the fifth transistor and a gate electrode of the sixth transistor, and

wherein the power supply line is electrically connected to a second terminal of the first transistor and a second terminal of the fourth transistor.

11. The semiconductor device according to claim 10 ,

wherein the first transistor comprises a channel formation region comprising an oxide semiconductor,

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor,

wherein the fourth transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the fifth transistor comprises a channel formation region comprising an oxide semiconductor.

12. The semiconductor device according to claim 10 ,

wherein the first photosensor is configured to perform a first reset operation by supplying a first signal to a second electrode of the first light-receiving element from a first time to a second time,

wherein a light source is configured to perform an irradiation of light to an object from the second time to a fifth time,

wherein the first photosensor is configured to perform a first detection of the light reflected off the object from the second time to the fifth time,

wherein the second photosensor is configured to perform a second reset operation by supplying a second signal to a second electrode of the second light-receiving element from a fourth time to the fifth time,

wherein the second photosensor is configured to perform a second detection of the light reflected off the object from the fifth time to a seventh time,

wherein the light source is configured to perform the irradiation n times,

wherein the first photosensor is configured to perform the first detection n times,

wherein the second photosensor is configured to perform the second detection n times,

wherein a distance x from the semiconductor device to the object is obtained by:

x

=

c

×

T

×

S

⁢

⁢

2

2

×

(

S

⁢

⁢

1

+

S

⁢

⁢

2

)

wherein S1 is a detection signal corresponding to the amount of charge generated by the first light-receiving element in the first detection,

wherein S2 is a detection signal corresponding to the amount of charge generated by the second light-receiving element in the second detection,

wherein T is a time length from the second time to the fourth time,

wherein n is a natural number of 2 or more, and

wherein c is light speed.

13. A semiconductor device comprising:

a first photosensor comprising a first light-receiving element, a second transistor, and a third transistor; and

a second photosensor comprising a second light-receiving element, a fourth transistor, a fifth transistor, and a sixth transistor,

wherein a first electrode of the first light-receiving element is electrically connected to a first terminal of the second transistor,

wherein a second terminal of the second transistor is electrically connected to a gate electrode of the third transistor,

wherein a first electrode of the second light-receiving element is directly connected to a first terminal of the fourth transistor and a first terminal of the fifth transistor,

wherein a gate electrode of the fourth transistor is directly connected to a second terminal of the fifth transistor and a gate electrode of the sixth transistor, and

wherein the first light-receiving element overlaps with the second light-receiving element.

14. The semiconductor device according to claim 13 ,

wherein the first light-receiving element is configured to detect visible light, and

wherein the second light-receiving element is configured to detect infrared light.

15. The semiconductor device according to claim 14 ,

wherein the second transistor comprises a channel formation region comprising an oxide semiconductor,

wherein the fourth transistor comprises a channel formation region comprising an oxide semiconductor, and

wherein the fifth transistor comprises a channel formation region comprising an oxide semiconductor.

16. The semiconductor device according to claim 14 ,

wherein the second photosensor is configured to perform a reset operation by supplying a signal to a second electrode of the second light-receiving element from a first time to a second time,

wherein a light source is configured to perform an irradiation of light to an object from the second time to a fourth time,

wherein the second photosensor is configured to perform a detection of the light reflected off the object from the second time to the fourth time,

wherein the light source is configured to perform the irradiation n times,

wherein the second photosensor is configured to perform the detection n times,

wherein a distance x from the semiconductor device to the object is obtained by:

x

=

c

2

×

(

T

-

S

⁢

⁢

1

n

×

k

)

wherein S1 is a detection signal corresponding to the amount of charge generated by the second light-receiving element in the detection,

wherein T is a time length from the second time to the fourth time,

wherein n is a natural number of 2 or more,

wherein c is light speed,

wherein k is a constant, and

wherein the first photosensor is configured to perform a second detection of the light transmitted through the first light-receiving element while the second photosensor performs the detection n times.

17. The semiconductor device according to claim 14 ,

wherein a light source is configured to perform an irradiation of light to an object from a first time to a fourth time,

wherein the second photosensor is configured to perform a reset operation by supplying a signal to a second electrode of the second light-receiving element from a third time to the fourth time,

wherein the second photosensor is configured to perform a detection of the light reflected off the object from the fourth time to a sixth time,

wherein the light source is configured to perform the irradiation n times,

wherein the second photosensor is configured to perform the detection n times,

wherein a distance x from the semiconductor device and the object is obtained by:

x

=

c

×

S

⁢

⁢

2

2

×

n

×

k

wherein S2 is a detection signal corresponding to the amount of charge generated by the second light-receiving element in the detection,

wherein n is a natural number of 2 or more,

wherein c is light speed,

wherein k is a constant, and

wherein the first photosensor is configured to perform a second detection of the light transmitted through the first light-receiving element while the second photosensor performs the detection n times.

18. The semiconductor device according to claim 14 ,

wherein the second photosensor is configured to perform a first reset operation by supplying a signal to a second electrode of the second light-receiving element from a first time to a second time,

wherein a light source is configured to perform a first irradiation of first light to an object from the second time to a fourth time,

wherein the second photosensor is configured to perform a first detection of the first light reflected off the object from the second time to the fourth time,

wherein the light source is configured to perform a second irradiation of second light to the object from a twelfth time to a fifteenth time,

wherein the second photosensor is configured to perform a second reset operation by supplying the signal to the second electrode of the second light-receiving element from a fourteenth time to the fifteenth time,

wherein the second photosensor is configured to perform a second detection of the second light reflected off the object from the fifteenth time to a seventeenth time,

wherein the light source is configured to perform the first irradiation n times,

wherein the light source is configured to perform the second irradiation n times,

wherein the second photosensor is configured to perform the first detection n times,

wherein the second photosensor is configured to perform the second detection n times,

wherein a distance x from the semiconductor device to the object is obtained by:

x

=

c

×

T

×

S

⁢

⁢

2

2

×

(

S

⁢

⁢

1

+

S

⁢

⁢

2

)

wherein S1 is a detection signal corresponding to the amount of charge generated by the second light-receiving element in the first detection,

wherein S2 is a detection signal corresponding to the amount of charge generated by the second light-receiving element in the second detection,

wherein T is a time length from the second time to the fourth time,

wherein c is light speed, and

wherein the first photosensor is configured to perform a third detection of the first light and the second light transmitted through the first light-receiving element while the second photosensor performs the first detection n times and the second detection n times.