Ranging sensor and ranging module
A ranging sensor includes a pixel including a photoelectric conversion element, a first storage node and a second storage node that store charge transferred from the photoelectric conversion element, a first transfer gate and a second transfer gate connected to the photoelectric conversion element so as to branch and transfer the charge generated in the photoelectric conversion element to different paths, a third transfer gate connected between the first storage node and the first transfer gate, a fourth transfer gate connected between the second storage node and the second transfer gate, a fifth transfer gate connected between the first storage node and the second transfer gate, and a sixth transfer gate connected between the second storage node and the first transfer gate, the ranging sensor including a transfer gate drive unit that drives each of the first to sixth transfer gates.
1 . A ranging sensor comprising:
a pixel including
a photoelectric conversion element,
a first storage node and a second storage node that store charge transferred from the photoelectric conversion element,
a first transfer gate and a second transfer gate connected to the photoelectric conversion element so as to branch and transfer the charge generated in the photoelectric conversion element to different paths,
a third transfer gate connected between the first storage node and the first transfer gate,
a fourth transfer gate connected between the second storage node and the second transfer gate,
a fifth transfer gate connected between the first storage node and the second transfer gate, and
a sixth transfer gate connected between the second storage node and the first transfer gate; and
a transfer gate drive unit that drives each of the first to sixth transfer gates.
2 . The ranging sensor according to claim 1 , wherein
the pixel includes
a floating diffusion region,
a seventh transfer gate connected between the first storage node and the floating diffusion region, and
an eighth transfer gate connected between the second storage node and the floating diffusion region.
3 . The ranging sensor according to claim 1 , wherein
the pixel includes an overflow gate that discharges the charge generated in the photoelectric conversion element.
4 . The ranging sensor according to claim 1 , wherein
the photoelectric conversion element receives reflected light of light emitted by a light emitter that performs pulse light emission, and
the transfer gate drive unit performs ON/OFF control of the first transfer gate and the second transfer gate by a pulse signal that drives the light emitter.
5 . The ranging sensor according to claim 1 , wherein
the transfer gate drive unit controls each of the first to sixth transfer gates such that the charge is accumulated in the second storage node via the second transfer gate while the charge is accumulated in the first storage node via the first transfer gate, and controls each of the first to sixth transfer gates such that the charge is accumulated in the first storage node via the second transfer gate while the charge is accumulated in the second storage node via the first transfer gate.
6 . The ranging sensor according to claim 5 , wherein
the transfer gate drive unit controls the fifth transfer gate to be turned off while controlling the third transfer gate to be turned on, and controls the sixth transfer gate to be turned off while controlling the fourth transfer gate to be turned on.
7 . The ranging sensor according to claim 6 , wherein
the transfer gate drive unit controls the third transfer gate and the fourth transfer gate to be turned on during a first period and controls the fifth transfer gate and the sixth transfer gate to be turned on during a second period different from the first period, and
a length of the first period is equal to a length of the second period.
8 . The ranging sensor according to claim 6 , wherein
a length of a period during which the charge is accumulated via the first transfer gate and a length of a period during which the charge is accumulated via the second transfer gate in the first storage node are both equal to a length of a period during which the charge is accumulated via the first transfer gate and a length of a period during which the charge is accumulated via the second transfer gate in the second storage node.
9 . The ranging sensor according to claim 1 , wherein
the transfer gate drive unit drives each of the third transfer gate, the fourth transfer gate, the fifth transfer gate, and the sixth transfer gate by three levels.
10 . The ranging sensor according to claim 9 , wherein
the driving by three levels includes driving with negative bias.
11 . The ranging sensor according to claim 10 , wherein
the transfer gate drive unit drives, with negative bias, the third transfer gate, the fourth transfer gate, the fifth transfer gate, and the sixth transfer gate during a read period of the charge accumulated in the first storage node and the second storage node.
12 . The ranging sensor according to claim 1 , further comprising
a plurality of the pixels.
13 . The ranging sensor according to claim 1 , further comprising
a pixel array unit in which the pixels are two-dimensionally arrayed.
14 . A ranging module comprising:
a light emitter that performs pulse light emission; and
a ranging sensor including a pixel including a photoelectric conversion element that receives reflected light of light emitted from the light emitter, the ranging sensor including a transfer gate drive unit that drives a plurality of transfer gates, wherein
the pixel includes
the photoelectric conversion element,
a first storage node and a second storage node that store charge transferred from the photoelectric conversion element,
a first transfer gate and a second transfer gate connected to the photoelectric conversion element so as to branch and transfer the charge generated in the photoelectric conversion element to different paths,
a third transfer gate connected between the first storage node and the first transfer gate,
a fourth transfer gate connected between the second storage node and the second transfer gate,
a fifth transfer gate connected between the first storage node and the second transfer gate, and
a sixth transfer gate connected between the second storage node and the first transfer gate.