A focus detection device includes line sensors which each photoelectrically convert
and integrate light from an object so as to output the received light as an image
signal; monitor sensors provided adjacent to the line sensors; a control device
which controls an integration operation of a predetermined line sensor and a predetermined
monitor sensor; and a detection device which detects that a monitor signal of each
of the monitor sensors reaches a predetermined termination value for terminating
integration of the corresponding line sensor after the control device allows the
predetermined line sensor and monitor sensor to start the integration. The control
device outputs a first termination signal from a first control terminal when the
detection device detects the monitor signal first reaching the termination value,
and thereafter outputs integration termination information of the respective monitor
sensors detected sequentially from the first control terminal.
