Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2001-11-28
2003-01-21
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S211000, C345S690000
Reexamination Certificate
active
06509884
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a display device for displaying an image with luminance corresponding to a video signal inputted from the exterior and a luminance control method therefor.
BACKGROUND ART
Plasma display devices using PDPs (Plasma Display Panels) have the advantage that thinning and larger screens are possible. In the plasma display devices, images are displayed by utilizing light emission in cases where discharge cells composing pixels are-discharged. As light is thus emitted, heat is generated on a glass surface composing the PDP, so that the higher the luminance of an image. becomes, the larger the amount of heat generation becomes. Therefore, the temperature of the glass surface is raised. In the worst case, the glass surface is damaged.
In order to solve the above-mentioned problem, an example of a conventional display device is a display device disclosed in JP-A-11-194745. In the display device, the whole surface of a display screen is divided into a plurality of blocks, temperature estimated values are calculated with respect to all the blocks, and the maximum value of the calculated estimated temperatures is compared with a reference temperature to produce a luminance correction coefficient. The luminance of the display screen is controlled by the luminance correction coefficient.
A display on which an image is displayed is generally fixed in its outer periphery. Damage to the display caused by the rise in the temperature with the increase in the luminance may occur in the vicinity of the outer periphery of the display in most cases. That is, the damage to the display depends on the temperature difference rather than the maximum temperature. Generally, the temperature difference between the outer periphery of the display where no heat is generated and the outer periphery of the display screen of the display where heat is generated is the largest. The display may be damaged by thermal stress created by the temperature difference in many cases.
In the conventional display device, however, only when the maximum value of the estimated temperatures reaches not less than the reference temperature, that is, when the temperature of any portion on the display screen exceeds its certain upper-limit value, the luminance is controlled. Therefore, the luminance cannot be always controlled when excessive thermal stress is exerted on the outer periphery, which is most easily damaged, of the display, thereby making it impossible to reliably prevent the display from being damaged.
In the conventional display device, the whole of the display screen is divided into a plurality of blocks, and the stimated temperatures are calculated with respect to all the blocks. Accordingly, operation processing becomes complicated, and long time is required to perform the operation processing. Particularly in recent years, it has been desired to make a display image highly precise. The number of pixels composing the display screen, that is, the number of discharge cells has tended to be increased. In this case, the above-mentioned operation processing has increasingly become complicated, and the processing time is lengthened.
DISCLOSURE OF INVENTION
An object of the present invention is to provide a display device capable of more reliably preventing a display from being damaged and a luminance control method therefor.
Another object of the present invention is to provide a display device capable of more reliably preventing a display from being damaged in a small amount of operation and a luminance control method therefor.
A display device according to an aspect of the present invention comprises a display for displaying an image with luminance corresponding to a video signal inputted from the exterior; a temperature estimation circuit for estimating from the video signal a temperature estimated value corresponding to the temperature of a display screen of the display; an operation circuit for finding a temperature difference estimated value using a reference value corresponding to the temperature of the outer periphery of the display and the temperature estimated value; and a control circuit for controlling the luminance of the image displayed on the display on the basis of the temperature difference estimated value.
In the display device, the temperature estimated value corresponding to the temperature of the display screen of the display is estimated from the video signal, and the temperature difference estimated value is found using the temperature estimated value and the reference value corresponding to the temperature of the outer periphery of the display, to control the luminance of the image displayed on the display on the basis of the temperature difference estimated value. Generally, the display on which the image is displayed is fixed in its outer periphery. Accordingly, damage to the display caused by the rise in the temperature with the increase in the luminance may occur in the vicinity of the outer periphery of the display in most cases. Therefore, the luminance is controlled depending on the temperature difference estimated value found from the temperature estimated value corresponding to the temperature of the display screen and the temperature of the outer periphery of the display, as described above, so that the luminance can be controlled on the basis of the temperature difference between the outer periphery of the display which most greatly affects the damage to the display and the display screen, thereby making it possible to more reliably prevent the display from being damaged.
It is preferable that the temperature estimation circuit estimates the temperature estimated value corresponding to the temperature of the outer periphery of the display screen of the display.
In this case, the temperature difference estimated value corresponding to the temperature of the outer periphery of the display screen of the display is estimated from the video signal, and the temperature difference estimated value is found using the temperature estimated value and the reference value corresponding to the temperature of the outer periphery of the display, to control the luminance of the image displayed on the display on the basis of the temperature difference estimated value. The temperature difference estimated value is found from the temperature estimated value corresponding to the temperature of the outer periphery of the display screen and the reference value corresponding to the temperature of the outer periphery of the display. Accordingly, the luminance can be controlled on the basis of the temperature difference between the outer periphery of the display which greatly affects the damage to the display and the outer periphery of the display screen closest to the outer periphery, thereby making it possible to more reliably prevent the display from being damaged. Further, the temperature estimated value operated in order to find the temperature difference estimated value is limited to the temperature estimated value for the outer periphery of the display screen of the display. Accordingly, the amount of operation is made smaller than that in a case where the temperature estimated value on the whole of the display screen, so that the processing is simplified, and the processing time is shortened. As a result, it is possible to more reliably prevent the display from being damaged in a small amount of operation.
It is preferable that the display comprises first and second boards between which a plurality of light emitting elements are formed and to which its outer periphery is fixed, and the outer periphery of the display includes a portion between the light emitting element positioned in the outermost periphery out of the plurality of light emitting elements and a fixed portion of the first and second boards.
In this case, the reference value corresponds to the temperature of the portion between the light emitting element positioned in the outermost periphery and the fixing portion of the first and second boards. Accordingly, the luminance can be controlled using as
Ishikawa Yuichi
Kasahara Mitsuhiro
Morita Tomoko
Chang Kent
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
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