Distance image capturing device and distance image capturing method

A distance image capturing method using a distance image capturing device including:

• a light source unit configured to emit an optical pulse to a measurement space;
• a light receiving unit including a pixel circuit in which a plurality of pixels are arranged in a two-dimensional matrix, the pixels each having a photoelectric conversion element that generates charges according to incident light and a plurality of charge accumulation units that accumulate the charges, and a pixel drive circuit that distributes and accumulates the charges in each of the charge accumulation units at a predetermined accumulation timing synchronized with an emission timing at which the optical pulse is emitted;
• and
• a distance image processing unit configured to calculate a distance to a subject present in the measurement space based on an amount of the charges accumulated in each of the charge accumulation units,
• wherein the distance image processing unit
• performs pre-measurement by a driving method that allows calculation of the distance and a reflectivity of the subject present in the measurement space,
• calculates the distance to the subject and the reflectivity of the subject as a situation of the subject present in the measurement space based on a measurement result of the pre-measurement,
• performs main measurement based on the situation of the subject present in the measurement space, and
• selects, in the main measurement, whether to perform high dynamic range (HDR) driving that expands a measurement range or to perform normal driving that does not expand the measurement range, based on the situation.

A distance image capturing device comprising:

• a light source unit configured to emit an optical pulse to a measurement space;
• a light receiving unit including:
• a pixel circuit in which a plurality of pixels are arranged in a two-dimensional matrix, the pixels each having a photoelectric conversion element that generates charges according to incident light and a plurality of charge accumulation units that accumulate the charges, and
• a pixel drive circuit that distributes and accumulates the charges in each of the charge accumulation units at a predetermined accumulation timing synchronized with an emission timing at which the optical pulse is emitted;
• and
• a distance image processing unit configured to calculate a distance to subjects present in the measurement space based on an amount of the charges accumulated in each of the charge accumulation units,
• wherein the distance image processing unit
• performs pre-measurement by a driving method that allows calculation of the distance and a reflectivity of the subjects present in the measurement space,
• calculates the distance to the subjects and the reflectivity of the subjects as a situation of the subjects present in the measurement space based on a measurement result of the pre-measurement,
• performs main measurement based on the situation of the subjects present in the measurement space, and
• selects, in the main measurement, whether to perform high dynamic range (HDR) driving that expands a measurement range or to perform normal driving that does not expand the measurement range, based on the situation, and
• the distance image processing unit
• performs, in the pre-measurement, a plurality of measurements, each of which has a different number of times of integration for repeating processing of accumulating the charges in each of the charge accumulation units,
• calculates relative reflectivities of the subjects present in the measurement space based on the measurement result of the pre-measurement, and
• determines, as the situation, whether or not a difference in reflectivities between the subjects present in the measurement space is equal to or greater than a threshold value,
• whether or not a subject included in the subjects having a low reflectivity is present at a short distance, and
• whether or not a subject included in the subjects having a high reflectivity is present at a long distance in the measurement space.