US 2003/0189558 A1 · Contrast adjusting circuitry and video display apparatus using same

Abstract

With the aim of offering a video display technique by which stable and high contrast video images are reproduced, contrast adjusting circuitry is constructed. The contrast adjusting circuitry detects a maximum picture level (MPL) and an average picture level (APL) of analog-to-digital converted luminance signals for a predetermined period, determines one of the predefined luminance regions within which the MPL falls and one of the predefined luminance regions within which the APL falls, and, based on the thus determined luminance regions of both MPL and APL, carries out a contrast adjustment of video images by changing the gain of luminance signals and color depth correction by changing the gain of color signals. By means of the illuminating optics and color synthesis optics of a projector using three video display elements, alleviating color heterogeneity and uneven luminance and offering high contrast images are achieved at reduced cost, and the convergence drift of an enlarged image displayed on the screen can be alleviated.

Claims18

Dependent claims

Contrast adjusting circuitry for use in a video display apparatus which converts analog video signals to digital video signals and displays video images, the contrast adjusting circuitry including:

amplifying means;
and
A/D conversion means for analog-to-digital conversion of video signals amplified by said amplifying means;
wherein said contrast adjusting circuitry is constructed to perform a contrast adjustment by changing the gain made by said amplifying means, based on maximum picture level data and average picture level data for analog-to-digital converted luminance signals.

1 more element

Contrast adjusting circuitry for use in a video display apparatus which converts analog video signals to digital video signals and displays video images, the contrast adjusting circuitry comprising:

amplifying means;
A/D conversion means for analog-to-digital conversion of video signals amplified by said amplifying means;
a first circuit for detecting a maximum picture level and an average picture level of analog-to-digital converted luminance signals for a predetermined period;
and
a second circuit for determining a first luminance region within which the maximum picture level falls and a second luminance region within which the average picture level falls and controlling the gain of analog luminance signals before A/D conversion and/or digital luminance signals after A/D conversion, based on the first luminance region data and the second luminance region data;
wherein said contrast adjusting circuitry makes an automatic adjustment of at least the contrast of video images.

3 more elements

A video display apparatus which converts analog video signals to digital video signals and displays video images, the video display apparatus comprising:

a detection circuit for detecting a maximum picture level and an average picture level of analog-to-digital converted luminance signals for a predetermined period;
a control circuit for determining a first luminance region within which the detected maximum picture level falls and a second luminance region within which the average picture level falls and controlling the gain of analog luminance signals before A/D conversion and/or digital luminance signals after A/D conversion, based on the first luminance region data and the second luminance region data or only the second luminance region data;
a color matrix circuit for converting digital color signals and digital luminance signals into red, green, and blue digital video signals and outputting the red, green, and blue digital video signals;
and
a display unit for displaying video images reproduced from the digital video signals output from the color matrix circuit.

2 more elements

Dependencies are inferred from the claim text.

Contrast adjusting circuitry and video display apparatus using same

Life of this patent

Contrast adjusting circuitry and video display apparatus using same

Life of this patent

Abstract

Claims18