Distance measuring apparatus and distance measuring method

1 . A distance measuring apparatus, comprising:

a light-receiving unit configured to receive reflected light from a distance measurement target, wherein the reflected light is based on irradiation light from a light-emitting unit;

a histogram acquiring unit configured to acquire a histogram indicating a frequency of reception of the reflected light at the light-receiving unit; and

an operation unit configured to:

calculate a distance to the distance measurement target based on a time corresponding to a peak of the histogram acquired by the histogram acquiring unit, and

correct the calculated distance based on a shape of the histogram acquired by the histogram acquiring unit, wherein

the shape of the histogram comprises a spreading state around a peak of a distribution of the reflected light from the distance measurement target, and

the spreading state is obtained based on conduction of a specific statistical process on the histogram acquired by the histogram acquiring unit.

2 . The distance measuring apparatus according to claim 1 , wherein a light-receiving element of the light-receiving unit comprises an avalanche photodiode configured to operate in a Geiger mode.

3 . The distance measuring apparatus according to claim 2 , wherein the light-receiving element of the light-receiving unit comprises a single-photon avalanche diode.

4 . The distance measuring apparatus according to claim 1 , wherein the distance measurement target is an object that causes subsurface scattering.

5 . The distance measuring apparatus according to claim 4 , wherein the histogram acquiring unit includes

a time difference detector configured to detect a time from a time point when the light-emitting unit emits the irradiation light to reception of the reflected light from the distance measurement target at the light-receiving unit, and

an accumulator configured to produce the histogram based on the time detected by the time difference detector.

6 . The distance measuring apparatus according to claim 1 , wherein the operation unit is further configured to:

measure the spreading state around the peak of the distribution of the reflected light from the distance measurement target,

calculate a correction amount from the spreading state around the peak, and

perform correction based on the calculated correction amount calculated.

7 . The distance measuring apparatus according to claim 6 , wherein the operation unit is further configured to perform the correction of the distance based on subtraction of the correction amount calculated from the spreading state around the peak from the peak of the distribution of the reflected light.

8 . The distance measuring apparatus according to claim 7 , wherein the distribution of the reflected light is a distribution obtained based on subtraction of an environment light component from the histogram acquired by the histogram acquiring unit.

9 . The distance measuring apparatus according to claim 8 , wherein the spreading state around the peak of the distribution of the reflected light comprises a standard deviation.

10 . The distance measuring apparatus according to claim 9 , wherein the correction amount calculated from the spreading state around the peak comprises an inverse of an exponential distribution parameter determined from the standard deviation.

11 . A distance measuring method, comprising:

in a distance measuring apparatus:

receiving reflected light from a distance measurement target, wherein the reflected light is based on irradiation light from a light-emitting unit;

acquiring a histogram indicating a frequency of reception of the reflected light;

calculating a distance to the distance measurement target based on a time corresponding to a peak of the acquired histogram; and

correcting the calculated distance based on a shape of the acquired histogram, wherein

the shape of the histogram comprises a spreading state around a peak of a distribution of the reflected light from the distance measurement target, and

the spreading state is obtained based on conduction of a specific statistical process on the acquired histogram.