Distance image measurement device and distance image measurement method

1. A distance image measurement device comprising:

a light source configured to generate pulsed light;

a light source controller configured to control the light source so that the light source regularly and repeatedly generates the pulsed light with a first duration in first to N-th (N is an integer equal to or greater than 2) subframe periods included in one frame period;

a pixel circuit part including a photoelectric conversion region configured to convert light into charge, first to M-th (M is an integer equal to or greater than 2) charge readout regions provided in proximity to the photoelectric conversion region and apart from each other, a charge discharge region for discharging the charge, and first to (M+1)-th control electrodes provided in correspondence to the photoelectric conversion region, the first to M-th charge readout regions, and the charge discharge region, for applying first to (M+1)-th control pulses for charge transfer between the photoelectric conversion region and the first to M-th charge readout regions, and charge transfer between the photoelectric conversion region and the charge discharge region, respectively;

a charge transfer controller configured to sequentially apply the first to M-th control pulses to the first to M-th control electrodes during a second duration, the second duration being equal to or longer than the first duration, in correspondence to the generation of the pulsed light by the light source controller, and apply the (M+1)-th control pulse to the (M+1)-th control electrode during a period other than application periods of the first to M-th control pulses;

a detector configured to read out voltages of the first to M-th charge readout regions of the pixel circuit part as first to M-th detection signals after the application of the first to M-th control pulses by the charge transfer controller; and

a calculator configured to repeatedly calculate a distance on the basis of the first to M-th detection signals,

wherein the charge transfer controller sets timings of the first to M-th control pulses so that delay times of the first to M-th control pulses with respect to a generation timing of the pulsed light are shifted to a time differing between first to N-th (N is an integer equal to or greater than 2) subframe periods in one frame period, and

the voltage detector reads out the voltages of the respective first to M-th charge readout regions generated according to the application of the first to M-th control pulses, as the first to M-th detection signals, in each subframe period of a period set with a weight.

2. The distance image measurement device according to claim 1 , wherein the calculator calculates the distance using the first to M-th detection signals detected according to the application of the first to M-th control pulses in each of the first to N-th subframe periods.

3. The distance image measurement device according to claim 1 , wherein the calculator calculates the distance using the first to M-th detection signals detected according to the application of the first to M-th control pulses in two of the first to N-th subframe periods.

4. The distance image measurement device according to claim 1 , wherein the number of repetitions of the pulsed light in the respective first to N-th (N is an integer equal to or greater than 2) subframe periods in one frame period is weighted to increase as a delay time of the first to M-th control pulses with respect to the generation timing of the pulsed light increases.

5. The distance image measurement device according to claim 1 , wherein the charge transfer controller performs a setting so that a rate of the number of applications of at least the first control pulse among the sequentially applied first to M-th control pulses decreases as a delay time of the first to M-th control pulses with respect to the generation timing of the pulsed light becomes shorter during the first to N-th subframe periods.

6. The distance image measurement device according to claim 5 , wherein the charge transfer controller performs a setting so that the number of applications of at least the first control pulse among the sequentially applied first to M-th control pulses is thinned out as the delay time of the first to M-th control pulses with respect to the generation timing of the pulsed light becomes shorter during the first to N-th subframe periods.

7. The distance image measurement device according to claim 1 , wherein the intensity of the pulsed light in each of the first to N-th subframe periods in the one frame period is weighted to decrease as the delay time of the first to M-th control pulses with respect to the generation timing of the pulsed light becomes shorter.

8. The distance image measurement device according to claim 1 , wherein control is performed so that a capacitance of the first to M-th charge readout regions increases as the delay time of the first to M-th control pulses with respect to the generation timing of the pulsed light becomes shorter in each of the first to N-th subframe periods in the one frame period.

9. The distance image measurement device according to claim 1 , further comprising:

an image sensor having the pixel circuit unit arranged in a two-dimensional array.

10. A distance image measurement method comprising:

a light source control step of controlling, by a light source controller, a light source so that the light source regularly and repeatedly generates pulsed light with a first duration in first to N-th (N is an integer equal to or greater than 2) subframe periods included in one frame period;

a charge transfer control step of sequentially applying, by a charge transfer controller, the first to M-th control pulses for controlling transfer of charge to the first to M-th control electrodes during a second duration, the second duration being equal to or longer than the first duration, in correspondence to the generation of the pulsed light by the light source controller, and applying an (M+1)-th control pulse for controlling discharge of the charge to the (M+1)-th control electrode during a period other than application periods of the first to M-th control pulses, by using a pixel circuit part including a photoelectric conversion region configured to convert light into charge, first to M-th (M is an integer equal to or greater than 2) charge readout regions provided in proximity to the photoelectric conversion region and apart from each other, a charge discharge region for discharging the charge, and first to (M+1)-th control electrodes provided in correspondence to the photoelectric conversion region, the first to M-th charge readout regions, and the charge discharge region;

a voltage detection step of reading out, by a detector, voltages of the first to M-th charge readout regions of the pixel circuit part as first to M-th detection signals after the application of the first to M-th control pulses by the charge transfer controller; and

a distance calculation step of repeatedly calculating, by a calculator, a distance on the basis of the first to M-th detection signals,

wherein the charge transfer control step includes setting timings of the first to M-th control pulses so that delay times of the first to M-th control pulses with respect to a generation timing of the pulsed light are shifted to a time differing between first to N-th (N is an integer equal to or greater than 2) subframe periods in one frame period, and

the voltage detection step includes reading out the voltages of the respective first to M-th charge readout regions generated according to the application of the first to M-th control pulses, as the first to M-th detection signals, in each subframe period of a period set with a weight.