Distance measurement device
A distance measurement device includes a light emitting and receiving units, and a calculation unit that uses a time-of-flight to calculate an object distance. The calculation unit includes: a histogram generation unit; a composite peak portion estimation unit that estimates whether a composite peak portion is present in a histogram, the composite peak portion being a peak portion at which the received light intensity changes with respect to the time-of-flight with reference to a peak time-of-flight and which is obtained from a combination of distributions of intensity of light from objects, differences of distances to the objects from the device being within a predetermined range; a time-of-flight specification unit that specifies rise time and fall time; a base time-of-flight determination unit that determines a base time-of-flight based on the rise time or the fall time; and a distance calculation unit that uses the base time-of-flight to calculate the object distance.
1 . A distance measurement device, comprising:
a light emitting unit that emits pulsed light;
a light receiving unit that receives light including reflected light due to the pulsed light; and
a calculation unit that uses a time of flight of the light received by the light receiving unit to calculate an object distance as a distance to an object that reflects the pulsed light and outputs the reflected light,
the calculation unit including:
a histogram generation unit that generates a histogram representing received light intensity at the light receiving unit for each of a plurality of times of flight,
a composite peak portion estimation unit that estimates presence of a composite peak portion in the histogram,
the composite peak portion being a peak portion at which the received light intensity changes from an increasing state to a decreasing state with respect to the time of flight with reference to a peak time of flight and which is obtained from a combination of distributions of intensity of light from a plurality of objects, and
differences of distances to the plurality of objects from the distance measurement device being within a predetermined range,
a time of flight specification unit that specifies two times of flight matching with a first threshold received light intensity and a received light intensity of noise light including background light,
the first threshold received light intensity being higher than the received light intensity of noise light, and
the two times of flight including a rise time as the time of flight that is shorter and a fall time as the time of flight that is longer,
a base time of flight determination unit that determines a base time of flight that is a base for calculating the object distance based on the rise time or the fall time specified concerning the composite peak portion,
the base time of flight determination unit determining the base time of flight in a different way when estimating that the composite peak portion is present compared to when estimating that the composite peak portion is not present, and
a distance calculation unit that uses the base time of flight to calculate a distance to one of the plurality of objects as the object distance.
2 . A distance measurement device, comprising:
a light emitting unit that emits pulsed light;
a light receiving unit that receives light including reflected light due to the pulsed light; and
a calculation unit that uses a time of flight of the light received by the light receiving unit to calculate an object distance as a distance to an object that reflects the pulsed light and outputs the reflected light,
the calculation unit including:
a histogram generation unit that generates a histogram representing received light intensity at the light receiving unit for each of a plurality of times of flight,
a composite peak portion estimation unit that estimates presence of a composite peak portion in the histogram,
the composite peak portion being a peak portion at which the received light intensity changes from an increasing state to a decreasing state with respect to the time of flight with reference to a peak time of flight and which is obtained from a combination of distributions of intensity of light from a plurality of objects, and
differences of distances to the plurality of objects from the distance measurement device being within a predetermined range,
a time of flight specification unit that specifies two times of flight matching with a first threshold received light intensity and a received light intensity of noise light including background light,
the first threshold received light intensity being higher than the received light intensity of noise light, and
the two times of flight including a rise time as the time of flight that is shorter and a fall time as the time of flight that is longer,
a base time of flight determination unit that, when estimating that the composite peak portion is present, determines a base time of flight that is a base for calculating the object distance based on the rise time or the fall time specified concerning the composite peak portion, and when estimating that the composite peak portion is not present, determines the base time of flight as an intermediate time between the rise time and the fall time, and
a distance calculation unit that uses the base time of flight to calculate a distance to one of the plurality of objects as the object distance.
3 . A distance measurement device, comprising:
a light emitting unit that emits pulsed light;
a light receiving unit that receives light including reflected light due to the pulsed light; and
a calculation unit that uses a time of flight of the light received by the light receiving unit to calculate an object distance as a distance to an object that reflects the pulsed light and outputs the reflected light,
the calculation unit including:
a histogram generation unit that generates a histogram representing received light intensity at the light receiving unit for each of a plurality of times of flight,
a composite peak portion estimation unit that estimates presence of a composite peak portion in the histogram,
the composite peak portion being a peak portion at which the received light intensity changes from an increasing state to a decreasing state with respect to the time of flight with reference to a peak time of flight and which is obtained from a combination of distributions of intensity of light from a plurality of objects, and
differences of distances to the plurality of objects from the distance measurement device being within a predetermined range,
a time of flight specification unit that specifies two times of flight matching with a first threshold received light intensity and a received light intensity of noise light including background light,
the first threshold received light intensity being higher than the received light intensity of noise light, and
the two times of flight including a rise time as the time of flight that is shorter and a fall time as the time of flight that is longer,
a base time of flight determination unit that, when estimating that the composite peak portion is present, determines the rise time as the base time of flight, and
a distance calculation unit that uses the base time of flight to calculate a distance to one of the plurality of objects as the object distance.
4 . A distance measurement device, comprising;
a light emitting unit that emits pulsed light;
a light receiving unit that receives light including reflected light due to the pulsed light;
a housing that has a window that transmits the pulsed light and the light received by the light receiving unit and accommodates the light emitting unit and the light receiving unit; and
a calculation unit that uses a time of flight of the light received by the light receiving unit to calculate an object distance as a distance to an object that reflects the pulsed light and outputs the reflected light,
the calculation unit including:
a histogram generation unit that generates a histogram representing received light intensity at the light receiving unit for each of a plurality of times of flight,
a composite peak portion estimation unit that estimates presence of a composite peak portion in the histogram,
the composite peak portion being a peak portion at which the received light intensity changes from an increasing state to a decreasing state with respect to the time of flight with reference to a peak time of flight and which is obtained from a combination of distributions of intensity of light from a plurality of objects, and
differences of distances to the plurality of objects from the distance measurement device being within a predetermined range,
a time of flight specification unit that specifies two times of flight matching with a first threshold received light intensity and a received light intensity of noise light including background light,
the first threshold received light intensity being higher than the received light intensity of noise light, and
the two times of flight including a rise time as the time of flight that is shorter and a fall time as the time of flight that is longer,
a base time of flight determine unit that determines a base time of flight that is a base for calculating the object distance based on the rise time or the fall time specified concerning the composite peak portion, and
a distance calculation unit that uses the base time of flight to calculate a distance to one of the plurality of objects as the object distance,
wherein
the composite peak portion estimation unit estimates presence of a first composite peak portion as the composite peak portion, the first composite peak portion including clutter, which is reflected light due to the pulsed light in an interior of the housing and reflected light due to the pulsed light from an external object outside the distance measurement device, and
when it is determined that the first composite peak portion is present, the base time of flight determination unit determines the base time of flight based on the fall time.
5 . The distance measurement device according to claim 1 , further comprising an intermediate time specification unit that specifies, in the composite peak portion, a first intermediate time between two times of flight that match with the first threshold received light intensity and a second intermediate time between two times of flight that match with a second threshold received light intensity, wherein
the composite peak portion estimation unit estimates presence of a second composite peak portion as the composite peak portion, the second composite peak portion including reflected light due to the pulsed light from a plurality of external objects outside the distance measurement device, and
when it is estimated that the second composite peak portion is present, the base time of flight determination unit determines the base time of flight based on the rise time if the first intermediate time is earlier than the second intermediate time, and the base time of flight determination unit determines the base time of flight based on the fall time when the first intermediate time is later than the second intermediate time.
6 . The distance measurement device according to claim 1 , further comprising an intermediate time specification unit that specifies, in the composite peak portion, a first intermediate time between two times of flight that match with a third threshold received light intensity different from the first threshold received light intensity and a second intermediate time between two times of flight that match with a second threshold received light intensity lower than the first threshold received light intensity, wherein
the composite peak portion estimation unit estimates presence of a second composite peak portion as the composite peak portion, the second composite peak portion including reflected light due to the pulsed light from a plurality of external objects outside the distance measurement device, and
when it is estimated that the second composite peak portion is present, the base time of flight determination unit determines the base time of flight based on the rise time if the first intermediate time is earlier than the second intermediate time, and the base time of flight determination unit determines the base time of flight based on the fall time when the first intermediate time is later than the second intermediate time.
7 . The distance measurement device according to claim 5 , wherein
when it is estimated that the second composite peak portion is present, the base time of flight determination unit determines the base time of flight based on the rise time or the fall time when the first intermediate time is equal to the second intermediate time.
8 . The distance measurement device according to claim 4 , wherein
the base time of flight determination unit determines when a received light position of light including the reflected light agrees with a set clutter position, and determines the base time of flight when determining that the received light position agrees with the clutter position,
the distance calculation unit calculates the object distance when it is determined that the received light position agrees with the clutter position,
the histogram generation unit generates the histogram for one or more pixels, units of light reception by the light receiving unit,
the distance calculation unit calculates the object distance for the one or more pixels, and
the distance measurement device further includes a clutter position setting unit that sets the clutter position based on at least one of a statistic of received light intensity of the one or more pixels and a statistic of the object distance calculated for the one or more pixels.