Multiple video signal processing with selection between two polarization modes

#This invention relates to an image signal processing apparatus for displaying an image. More particularly, the invention relates to a signal processing apparatus for displaying signals from two signal sources on each of two display units.

#When video information is displayed on a display device such as a liquid-crystal display (referred to as an "LCD" hereinafter), it is necessary to prevent a residual image caused by DC components in the video signal. In the prior art, this is accomplished by using a method in which the polarity of the video signal is reversed at fixed periods.

#Further, head-mounted displays worn by an observer have been proposed in which two LCDs are used and video information for the left and right eyes of the observer is displayed on respective ones of the LCD. When two LCDs are used, however, it is necessary that the video signal be reversed in polarity on each signal path at fixed periods. One conventional method of achieving this is to provide each signal path with signal processing means for polarity reversal and signal processing means for no reversal of polarity and switch between the two means in each signal path. Another method is to provide each signal path with one signal processing means capable of switching between reversed/non-reversed polarity, and switch the polarity of the signal processing means per se to thereby change over the polarity of the video signal.

#The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

#FIG. 1 is a block diagram illustrating the construction of a signal processing apparatus according to a first embodiment of the present invention;

#FIG. 2 is a block diagram illustrating the construction of a signal processing apparatus according to a second embodiment of the present invention;

#Preferred embodiments of the present invention will be described in detail in accordance with the accompanying drawings.

#FIG. 1 is a block diagram showing the construction of a first embodiment of a signal processing apparatus according to the present invention. The apparatus includes a first signal source 1 for outputting a first video signal, a second signal source 2 for outputting a second video signal, a first display unit 3 for displaying the first video signal from the first signal source 1, a second display unit 4 for displaying the second video signal from the second signal source 2, a first driver 5 for supplying the first display unit 3 with the first video signal, a second driver 6 for supplying the second display unit 4 with the second video signal, a reversing unit 7 for reversing the polarity of the video signal from the first source 1 or second signal source 2, a first selector 8 for selectively inputting the video signal from the first source 1 or second signal source 2 to the reversing unit 7, a second selector 9 for selectively supplying the first driver 5 and the second driver 6 with the reversed video signal by the reversing unit 7, and a controller 10 for counting horizontal scanning signals of the signal sources 1, 2 and controlling the operation of the first selector 8 and second selector 9.

#The operation of this embodiment will now be described.