Patent ID: 7283171

Claim:
An image pickup apparatus comprising: an image pickup device configured to convert a monitored object image into an electrical image signal and to output the image signal; a processor configured to receive the image signal from the image pickup device and to generate a first brightness signal based on the received image signal; a clock generator configured to generate a constant cyclic drive frequency to drive the image pickup device; a brightness signal determining unit configured to determine whether the first brightness signal is less than a predetermined value; an external ranging device configured to determine a distance to the monitored object and to output a second brightness signal based on a brightness of the monitored object, a sensitivity to light of the external ranging device being higher than that of the image pickup device; an image signal reading unit configured to synchronize the image signal with a frequency based on the drive frequency and to read the image signal in a constant read frequency; a brightness signal obtaining unit configured to obtain the second brightness signal of the object from the external ranging device, when the brightness signal determining unit determines that the first brightness signal is less than the predetermined value; and a read frequency changing unit configured to change the read frequency based on the second brightness signal output by the external ranging device.