Patent ID: 7372474

Claim:
An image display controlling apparatus for adjusting the contrast of an image, said apparatus comprising: discriminating means for receiving an image signal, for discriminating a signal format of the image signal, the signal format including at least one of lightness of the image and color of the image, and for generating a discrimination signal based on the result of said discriminating; controller means for receiving the discrimination signal and for generating a control signal based on the received discrimination signal; level adjustment means for receiving the control signal and for adjusting a luminance signal level of the image signal based on the received control signal; display means for displaying an image in accordance with the adjusted luminance signal level; illuminating means for illuminating said display means, the brightness of the illumination provided by said illuminating means having a predetermined range below which stable discharge current cannot be maintained by said illuminating means; and illumination controlling means, including: switching regulator means for receiving the control signal, for periodically receiving notification of the brightness of the illumination provided by said illuminating means, and for generating a DC signal based on the received control signal and the periodically received notification of the brightness of the illumination provided by said illuminating means, and oscillator means for receiving the DC signal and for controlling the brightness of the illumination provided by said illuminating means based on the received DC signal; the control signal including a setting value associated with a particular image contrast such that if the setting value would require said illumination controlling means to lower the illumination brightness to be below the predetermined range, said illumination controlling means instead maintains the illumination brightness within the predetermined range to maintain the stable discharge current and said level adjustment means lowers the luminance signal level according to the setting value until the particular image contrast associated with the setting value is attained.