Time to digital converter, distance measuring device, and moving body
A time to digital conversion circuit includes a first measurement block and one or a plurality of second measurement blocks. The first measurement block activates a control signal in accordance with activation of a start signal and measures time from the activation of the start signal to a first edge of a common clock signal. The second measurement block includes a lower measurement circuit and an upper measurement circuit, which are enabled by the activation of the control signal. The lower measurement circuit measures time from activation of a stop signal to a second edge of the common clock signal, and the upper measurement circuit measures time from the first edge to the second edge.
1 . A time to digital conversion circuit comprising:
a first measurement block and one or a plurality of second measurement blocks,
wherein the first measurement block activates a control signal in accordance with activation of a start signal and measures time from the activation of the start signal to a first edge of a common clock signal,
the second measurement block includes a lower measurement circuit and an upper measurement circuit, which are enabled by the activation of the control signal, and
the lower measurement circuit measures time from activation of a stop signal to a second edge of the common clock signal, and the upper measurement circuit measures time from the first edge to the second edge.
2 . The circuit according to claim 1 , wherein
the first measurement block includes a first control circuit configured to activate the control signal in accordance with the activation of the start signal, and a measurement circuit configured to measure the time from the activation of the start signal to the first edge.
3 . The circuit according to claim 2 , wherein
the first control circuit outputs, as a second control signal, a signal obtained by synchronizing the control signal in accordance with the common clock signal,
the second measurement block includes a second control circuit, and
the second control circuit causes the upper measurement circuit to start measurement if the second control signal is activated next to the activation of the control signal, and
causes the lower measurement circuit to start measurement if the stop signal is activated in a state in which the control signal is activated.
4 . The circuit according to claim 3 , wherein
the second control circuit causes the upper measurement circuit to end the measurement in response to the second edge.
5 . The circuit according to claim 3 , wherein
the second control circuit causes the lower measurement circuit to end the measurement in response to the second edge.
6 . The circuit according to claim 3 , wherein
the first control circuit includes a first detection circuit configured to activate the control signal in asynchronism with the common clock signal in accordance with the activation of the start signal, and a second detection circuit configured to activate the second control signal in synchronism with the common clock signal in accordance with the activation of the control signal, and
the second detection circuit includes a first flip-flop configured to receive the control signal in response to a third edge of the common clock signal that arrives next to the activation of the control signal, and a second flip-flop configured to receive an output of the first flip-flop in response to a fourth edge of the common clock signal that arrives next to the third edge, thereby generating the second control signal.
7 . The circuit according to claim 3 , wherein
the second control circuit includes a third detection circuit configured to activate an output of itself in asynchronism with the common clock signal in accordance with the activation of the stop signal, and a fourth detection circuit configured to activate an output of itself in synchronism with the common clock signal in accordance with the activation of the output of the third detection circuit, and
the fourth detection circuit includes a third flip-flop configured to receive the output of the third detection circuit in response to a fifth edge of the common clock signal that arrives next to the activation of the output of the third detection circuit, and a fourth flip-flop configured to receive an output of the third flip-flop in response to a sixth edge of the common clock signal that arrives next to the fifth edge, thereby updating an output of itself.
8 . The circuit according to claim 1 , wherein
the second measurement block has the same configuration as the first measurement block.
9 . A distance measuring device comprising:
a pixel array including a plurality of pixels; and
a time to digital conversion circuit defined in claim 1 ,
wherein a plurality of second measurement blocks of the time to digital conversion circuit are arranged to receive a plurality of stop signals output from the pixel array.
10 . The device according to claim 9 , wherein
the plurality of pixels are arranged to form a plurality of rows and a plurality of columns, and
the plurality of second measurement blocks are provided in correspondence with the plurality of rows of the pixel array, respectively.
11 . The device according to claim 9 , wherein
the plurality of pixels are arranged to form a plurality of rows and a plurality of columns, and
the plurality of second measurement blocks are provided in correspondence with the plurality of pixels of the pixel array, respectively.
12 . The device according to claim 9 , wherein
the plurality of pixels are arranged to form a plurality of rows and a plurality of columns, and the plurality of pixels are divided into a plurality of groups, and
the plurality of second measurement blocks are provided in correspondence with the plurality of groups of the pixel array, respectively.
13 . The device according to claim 9 , wherein each of the plurality of pixels includes an avalanche photodiode.
14 . The device according to claim 9 , wherein each of the plurality of pixels includes an event detection type pixel.
15 . The device according to claim 9 , further comprising
a light-emitting unit; and
a control unit configured to send a light-emitting instruction to the light-emitting unit and send a start instruction to the time to digital conversion circuit.
16 . A moving body comprising:
a distance measuring device defined in claim 9 ; and
a control unit configured to control the moving body based on an output of the distance measuring device.