Detection device
According to an aspect, a detection device includes: a light source configured to emit light to an object to be detected; a plurality of photodiodes arranged in a detection area; one or more detection circuits; and a coupling switching circuit configured to switch coupling of one or more of the photodiodes to one or more of the detection circuits. The coupling switching circuit is configured to change the number of the detection circuits coupled to one or more of the photodiodes based on an output value from one or more of the photodiodes.
1 . A detection device comprising:
a light source configured to emit light to an object to be detected;
a plurality of photodiodes arranged in a detection area;
a plurality of signal lines coupled to the photodiodes;
a plurality of detection circuits; and
a coupling switching circuit configured to switch coupling of one or more of the photodiodes to one or more of the detection circuits, the coupling switching circuit being separate from each one of the plurality of detection circuits and connecting to each detection circuit via a respective output signal line, wherein
the coupling switching circuit is configured to change a number of the detection circuits coupled to one or more of the photodiodes based on an output value from one or more of the photodiodes, and
the coupling switching circuit comprises:
a signal line selection circuit including a first plurality of switches and a second plurality of switches, each one of the first plurality of switches coupled to a first output signal line and a respective photodiode in a first group of photodiodes, each one of the second plurality of switches coupled to a second output signal line and a respective photodiode in a second group of photodiodes, the first output signal line being different from the second output signal line, and the first group of photodiodes being different from the second group of photodiodes, the signal line selection circuit being configured to change a number of the signal lines coupled to one output signal line; and
a detection circuit selecting circuit including a plurality of switches, the plurality of switches configured to provide switching of each of the first output signal line and the second output signal line being connected with one or more detection circuits through a separate output signal line, the plurality of switches being connected to the first output signal line and the second output signal line as inputs to the detection circuit selecting circuit, the plurality of switches being connected to a third output signal line and a fourth output signal line which are respectively connected to different detection circuits, and the detection circuit selecting circuit configured to change
a first number of the detection circuits coupled to the one output signal line to
a second number of the detection circuits coupled to the one output signal line, where the first number and the second number are each one or more.
2 . The detection device according to claim 1 , wherein the signal line selection circuit comprises a switch that is provided for each of the signal lines and is configured to switch coupling between the one output signal line and one of the signal lines.
3 . The detection device according to claim 1 , wherein the light source is configured to change an emission intensity of light based on the output value from the photodiodes.
4 . The detection device according to claim 1 , wherein the light source is configured to change irradiation time of light based on the output value from the photodiodes.
5 . The detection device according to claim 1 , wherein
a partial area of the detection area is selected as a selected area based on the output value from the photodiodes, and
the coupling switching circuit is configured to couple the photodiodes in the selected area collectively to one or more of the detection circuits.
6 . The detection device according to claim 1 , wherein
the signal line selection circuit is configured to change the number of the signal lines coupled to the one output signal line to allow the signal lines to couple to one of the detection circuits, and
the detection circuit selecting circuit is configured to change the first number of the detection circuits coupled to the one output signal line to allow the detection circuits to couple to one of the signal lines.
7 . The detection device according to claim 1 , wherein
the output value includes:
a first output value that mainly corresponds to an amount of the light emitted from the light sources and that is output as a constant value regardless of a change in a state of the object to be detected; and
a second output value that is a detection value indicating an amount of a change in the light transmitted through the object to be detected caused by a change in the state of the object to be detected,
when the first output value is outside a valid range, a control circuit is configured to adjust a gain of the detection circuit,
when the first output value is within the valid range, a signal processing circuit determines whether the second output value of the output value from the detection circuit is within the valid range, and
if the second output value is out of a range, the control circuit is configured to switch a number of the photodiodes and the number of the detection circuits that are coupled to the one output signal line.