Matsushita Electric Industrial Co., Ltd.

Panasonic Corporation

Tetsuro Shiota

Hiroshi Miyai

Satoshi Hamada

Hitoshi Noda

Toshiyuki Noguchi

Hiroaki Satou

Shigeaki Yamano

Shingo Sugino

A diaphragm control angle calculating portioncalculates an angle at which a diaphragm is controlled to control an amount of light that reaches from a lampto a display deviceaccording to distribution information of an input video signal, such as the maximum value, the minimum value, the average value and the histogram of the signal, and the control angle is inputted to a fan control signal generating portionand a diaphragm driving portionas control angle information. The diaphragm driving portioncontrols the angle of the diaphragmbased on the control angle information. Light from the lampdriven by a lamp driving portionenters the diaphragm, and the amount of light according to the angle of the diaphragmenters the display device. The fan control signal generating portioncontrols the rotation speed of a cooling fanaccording to a combination of the control angle information and the temperature detected by a temperature sensor. A high-contrast display image can be produced while noise resulting from an increase in the rotation speed of the cooling fan can be suppressed and the reliability of the lamp can be ensured by avoiding the influence of the temperature.

Projection type image display device

A light-quantity adjusting function of a diaphragm used for light quantity control for improving the contrast of a projected image is controlled to cancel light quantity variation due to variation of the driving power of the light source for increasing the service life. This control keeps the quantity of light coming into a display element at a constant value and achieves both service life extension of the light source and image projection having no brightness fluctuation.

Image display device

In gray-scale correction where extension to a dynamic range is performed based on a maximum value and a minimum value of a video luminance signal, sufficient correction effects cannot be obtained in some displayed images. Therefore, a histogram detecting circuit (), a maximum value detecting circuit (), and a minimum value detecting circuit () respectively detects, for each field, a maximum value (Kmax) and a minimum value (Kmin) in a detection WINDOW set in a screen, and distribution information in a gray-scale direction. The detected maximum value (Kmax) and minimum value (Kmin) are respectively corrected by a maximum value correcting circuit () and a minimum value correcting circuit () based on the output results of the histogram detecting circuit (), and output as a corrected maximum value (Lmax) and a corrected minimum value (Lmin). Based on these corrected maximum value (Lmax) and a corrected minimum value (Lmin), an input video luminance signal is corrected. Thus, it is possible to obtain optimal effects of gray-scale correction in accordance with a scene.

Dynamic gray scale range adjustment apparatus and method

An image display device which has a display element that optically modulates an incident light for displaying an image. A lamp is a light source of the incident light to the display element. A lamp driver drives the lamp. A lamp power level calculator calculates a driving power level of the lamp corresponding to a level of an input video signal. A lamp temperature controller controls a lamp temperature depending on changes in the input signal from the lamp power level calculator so as to change the lamp temperature within a predetermined range in response to fluctuations of the input video signal. This image display device can further include a projection lens for projecting and displaying images formed in the display element on a screen.

Image display

An image display device has a first look-up table memory ( ) for correcting a gamma curve of an input video signal so as to correct a gradation of a display image, a second look-up table memory ( ) for generating uniformity correction data on a screen at each gradation level, and a positional information generating portion ( ) for generating uniformity correction data corresponding to a position on the screen. A correction data making portion ( ) synthesizes the uniformity correction data output from the second look-up table memory ( ) and the uniformity correction data output from the positional information generating portion ( ). An arithmetic processing circuit ( ) corrects the video signal that has been subjected to the gradation correction and read out from the first look-up table memory ( ) by using the uniformity correction data output from the correction data making portion ( ), and the uniformity correction of the display image is performed at all gradation levels.

A luminance correction circuit to correct areas of unevenness in luminance or color of a video image and smoothes gaps between correction blocks. The luminance correction circuit comprises a memory for storing correction data for correcting unevenness in luminance or color of video image, a timing generator for controlling read timing of the correction data from the memory, and an analog processor for processing the video signal using the correction data from the memory. A display area is divided to an appropriate number of blocks and the video signal is corrected in each block and the boundary between corrected blocks is smoothed by controlling the correction timing.

Luminance correction circuit and video display monitor thereof

In a projection type image display apparatus, the screen is divided and a memory to record luminance correction data corresponding to the divided regions is provided, and addresses of the divided regions of the screen are set by an address counter, synchronized with the input video signal. The luminance correction data are read successively by inputting the addresses to the memory, and luminance nonuniformity on the screen is corrected through operational processing of the correction value converted in an analog value by a D/A converter and the input video signal. The luminance correction data is obtained by computing measurement results of respective luminance characteristics of red, green, and blue colors on the screen and separately recorded as an amplitude correction component and a DC level correction component. By multiplying and adding the correction data to the input video signal respectively, nonuniformities in luminance and color from low luminance level to high luminance level can be precisely corrected. Also, as the read start position and read direction of the memory can be set corresponding to sweep direction of a projection type image display apparatus, the projection direction to the screen in a projection type image display apparatus can be easily changed without affecting the operation of luminance correction.

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Osaka, Japan

Tetsuro Shiota