The present invention generally relates to a screen saver apparatus and method, and in particular, to a screen saver apparatus and method based on monitoring the various changes of the signal representing an image being processed.
Screen saver applications for computer systems are well known. The purpose of a screen saver application is to prevent the burning of a fixed pattern onto the phosphor screen of a display, when there is little or no screen activity. The common way of detecting this inactivity is to monitor whether there is any user keyboard input. In other words, a timer is started after each keyboard entry and if the timer expires before another entry, then the screen saver application will cause the screen to go blank or display a predetermined moving image, thereby preventing screen burn. The screen will be restored as soon as another keyboard entry is detected.
Other prior screen saver systems take the approach of looking at the motion of the images being displayed. For example, Japanese Patent No. 6332418 A, assigned to Fujitsu General Ltd. of Japan, discloses a screen saver apparatus having a motion adaption circuit.
The motion adaption circuit examines a video signal and determines the motion characteristics of the corresponding image. If a still picture is detected, a timer is started. If the still picture is displayed after a predetermined time period, the power supply to the display is cut off, thereby preventing screen burn. These motion based systems are, however, complicated and typically requires costly digital processing circuitry to determine whether a motion is present. In addition, these systems enable the screen saver function based solely on the motion factor and nothing else, which may cause unnecessary blanking of the screen.
Another prior system is disclosed in Japanese patent publication number 09327031. This system determines the peak beam current value of one frame of video for a particular period. The system also detects the motion of an image based on an inter-frame of video reference. Thereafter, a brightness control unit reduces the beam current of the CRT gradually to a reference current value corresponding to the reference voltage value during the still picture display.
The above system, however, requires complicated and expensive circuitries. In particular, it detects the relative motion of an image by using a motion of an image by using a motion adaptive 3-dimension YC separation system. Theis requires costly components such as A/D converters and digital frame stores.
The present inventor recognizes the advantages of being able to implement a screen saver function for a multi-media display in a cost effective manner, preferably using the circuitry that is already being used for other functions.
In addition, the present inventor recognizes that there is no need to blank the screen, even if the screen is static for a period of time, if the image being displayed has characteristics that do not exceed certain thresholds. In other words, even if a screen image is static, there may be little chance of screen burn if the image being displayed is of low brightness and/or contrast, for example.
Therefore, in one exemplary embodiment, a method and system for implementing a screen saver function is described. A peak value of a characteristic such as beam current magnitude of a video signal being processed is determined. An average value of the same characteristic of the video signal is also determined. Changes in this average value is additionally monitored. Therefore, the characteristic of the video signal is adjusted only if the peak value exceeds a first threshold and a change less than a second threshold is detected in the average value.