Focus detection sensor

A focus detection sensor, comprising:

• a plurality of photoelectric conversion units configured to convert light into charges;
• a plurality of memory units configured to store charges generated by the photoelectric units as pixel signals;
• a plurality of transfer units configured to transfer the charges generated by the photoelectric conversion units to the memory units;
• a plurality of reset units configured to reset the photoelectric conversion units and the memory units;
• a detection unit configured to output a first detection signal in accordance with the pixel signals stored in the memory units;
• and
• a mode switching determination unit configured to perform switching from a first operation mode to a second operation mode, wherein the transfer units are set to a transfer state during a charge accumulation period after the photoelectric conversion units are reset in the first operation mode, and the transfer units are set to a non-transfer state during a charge accumulation period in the second operation mode, wherein
• the focus detection sensor further comprising:
• an accumulation end determination unit configured to terminate the charge accumulation period,
• the detection unit outputs a second detection signal in accordance with the pixel signals stored in the memory units,
• the accumulation end determination unit terminates the charge accumulation period in accordance with the detection signal, and
• the second detection signal corresponds to a largest value of the pixel signals stored in the memory units.