Provided is an automatic brightness stabilization (ABS) apparatus that
prevents brightness stabilization from being affected by dynamic focus
device and velocity modulation device. ABS apparatus includes an image
signal processing portion which inserts a predetermined pulse signal into
a vertical flyback period of an image signal and applies the resulting
signal to the electron gun, an ABS signal detecting portion which detects
the pulse signal affected by the electron gun, a velocity modulating
portion which generates a velocity modulation signal for emphasizing
luminance components of the image signal and applies the velocity
modulation signal to a velocity modulation coil of the CRT, and a retrace
cancelling portion which cancels the velocity modulation signal generated
by the velocity modulating portion, during a vertical flyback period.
Image signal processing portion compares the detected pulse signal with a
predetermined amplitude of the pulse signal and controls the
amplification degree of the image signal.