Range imaging device and range imaging method

A range imaging method, comprising:

• emitting light pulses into a measurement space by a light source of a range imaging device;
• integrating, in a plurality of charge storage units of at least one pixel circuit in the range imaging device in a frame cycle, a charge generated in a photoelectric conversion element of the at least one pixel circuit in the range imaging device due to light incident from the measurement space by the at least one pixel circuit of the range imaging device;
• distributing the charge to each of the charge storage units for integration therein by performing switching operation of transfer transistors at predetermined timing synchronizing with emission of the light pulses by a pixel drive circuit of the range imaging device;
• and
• calculating, based on a charge determined by a first charge that is a charge integrated in each of the charge storage units, a distance between an object in the measurement space and a light-receiving unit by circuity of the range imaging device, wherein
• the calculating calculates the distance by subtracting a second charge from each of the first charges such that the second charge is a noise charge as an integrated charge other than the charge distributed to the charge storage units for integration therein by the switching operation of the transfer transistors,
• any of the frames is a noise charge acquisition frame that acquires the second charge in the noise charge acquisition frame after emission of the light pulses from the light source, in a state in which no charge is integrated in the charge storage units from the photoelectric conversion element in response to the pixel drive circuit turning off the transfer transistors, the charge integrated in each of the charge storage units is the second charge, and
• in frames following the noise charge acquisition frame, in response to the pixel drive circuit turning on or off the transfer transistors, the charge is distributed to each of the charge storage units for integration therein as the first charge.

A range imaging method, comprising:

• distributing, through switching operation of a plurality of transfer transistors of at least one pixel circuit in a range imaging device that transfer charge in a frame cycle from a photoelectric conversion element of the at least one pixel circuit to a plurality of charge storage units of the at least one pixel circuit, charge generated in the photoelectric conversion element due to incident light from a measurement space to each of N charge storage units for integration therein in a predetermined integration cycle synchronizing with emission of light pulses, where N≥3, by a pixel drive circuit of the range imaging device;
• estimating, by circuitry of the range imaging device, second charge from an ambient light charge using a noise charge inflow ratio between the ambient light charge and a noise charge such that the ambient light charge is generated due to ambient light in the measurement space and distributed to the charge storage units for integration therein via the transfer transistors and that the noise charge is generated due to the ambient light and flowing into the charge storage units for integration therein without passing through the transfer transistors;
• and
• calculating, by the circuitry, a distance to an object using a corrected charge obtained by subtracting the second charge from each of first charges integrated in the charge storage units.