Distance measurement device, method of controlling distance measurement device, and electronic apparatus
A distance measurement device includes a light detection unit, an exposure control unit; a distance image calculator, a detector, and a control unit. The light detection unit receives light from a subject. The exposure control unit performs exposure control on the basis of a signal value outputted by the light detection unit. The distance image calculator calculates a distance image on the basis of an output of the light detection unit. The distance image includes depth and a confidence value. The detector detects, from a feature of data processed by the distance image calculator, a close and low-reflectance object whose distance is unmeasurable. The control unit dynamically controls at least one of a parameter of the exposure control unit or a parameter of the distance image calculator on the basis of a result of detection of the detector.
1 . A distance measurement device, comprising:
a light detection circuit configured to receive light from a subject;
an exposure control circuit configured to perform exposure control based on a signal value outputted by the light detection circuit;
a distance image calculator configured to calculate a distance image based on an output of the light detection circuit, wherein
the distance image includes depth and a confidence value,
the depth includes deepness information of the subject, and
the confidence value includes light reception information of the light detection circuit;
a detector configured to detect, from a feature of data processed by the distance image calculator, a close and low-reflectance object whose distance is unmeasurable; and
a control circuit configured to dynamically control a parameter of the distance image calculator based on a result of the detection of the detector.
2 . The distance measurement device according to claim 1 , wherein the feature includes one of an average depth value or a depth histogram created from the distance image.
3 . The distance measurement device according to claim 1 , wherein
the control circuit is further configured to control a parameter of the exposure control circuit, and
the parameter of the exposure control circuit includes exposure time.
4 . The distance measurement device according to claim 3 , wherein the control circuit is further configured to increase the exposure time in a case of true depth.
5 . The distance measurement device according to claim 1 , wherein
the distance image calculator has a function of a confidence value filter that invalidates a pixel having a confidence value less than or equal to a determined threshold, and
the parameter of the distance image calculator includes a threshold of the confidence value filter.
6 . The distance measurement device according to claim 5 , wherein the control circuit is further configured to decrease the threshold of the confidence value filter in a case of true depth.
7 . The distance measurement device according to claim 1 , wherein the detector is further configured to determine whether the subject is the close and low-reflectance object from the feature of final depth.
8 . The distance measurement device according to claim 7 , wherein the detector is further configured to execute at least one of:
a first process to determine that a number of valid pixels in a region of interest set in a screen is less than or equal to a first determined threshold,
a second process to determine that average depth of the valid pixels in the region of interest is less than or equal to a second determined threshold, or
a third process to determine that a number of valid pixels in a whole of the screen is greater than or equal to a third determined threshold.
9 . The distance measurement device according to claim 7 , wherein the detector is further configured to:
create a histogram indicating frequency of intermediate depth on one screen; and
determining determine whether the subject is a close object from the feature of the intermediate depth.
10 . The distance measurement device according to claim 9 , wherein the detector is further configured to execute at least one of:
a first process to determine that a mode of an intermediate depth histogram is less than or equal to a first determined threshold,
a second process to determine that a count value of the mode is within a determined range, or
a third process to determine that a cumulative count value less than or equal to a specific distance is greater than or equal to a second determined threshold.
11 . The distance measurement device according to claim 9 , wherein the detector is further configured to determine whether the subject is a low-reflectance object based on the confidence value.
12 . The distance measurement device according to claim 11 , wherein the detector is further configured to that an average value of confidence values of a region of interest set in a screen is within a determined range.
13 . A method of controlling a distance measurement device, the distance measurement device including a light detection circuit that receives light from a subject, an exposure control circuit that performs exposure control based on a signal value outputted by the light detection circuit, a distance image calculator that calculates a distance image based on an output of the light detection circuit, the distance image including depth and a confidence value, the depth including deepness information of the subject, the confidence value including light reception information of the light detection circuit, and a detector that detects, from a feature of data processed by the distance image calculator, a close and low-reflectance object whose distance is unmeasurable, the method comprising:
dynamically controlling a parameter of the distance image calculator based on a result of the detection of the detector.
14 . An electronic apparatus, comprising:
a distance measurement device that includes:
a light detection circuit configured to receive light from a subject;
an exposure control circuit configured to perform exposure control based on a signal value outputted by the light detection circuit;
a distance image calculator configured to calculate a distance image based on an output of the light detection circuit, wherein
the distance image includes depth and a confidence value,
the depth includes deepness information of the subject, and
the confidence value includes light reception information of the light detection circuit;
a detector configured to detect, from a feature of data processed by the distance image calculator, a close and low-reflectance object whose distance is unmeasurable; and
a control circuit configured to dynamically control a parameter of the distance image calculator on a basis of a result of the detection of the detector.