When a liquid crystal display device (LCD) displays a moving image, it displays a frame image (to be simply referred to as a frame hereinafter) at a rate of, e.g., 60 frames/sec.  The frame is a sequential scanning signal obtained by interlaced processing of, e.g., 60 fields/sec.  The LCD continues to display a frame during 1/60 sec. 
In viewing such an image displayed on the LCD, the human eye perceives an immediately preceding frame image as an afterimage.  For this reason, a moving object in the image may get blurred, or its motion may seem unnatural.  To prevent such blur in a moving image, a method is disclosed, which displays a moving image while inserting an interpolation frame between two continuous frames. 
Jpn.  Pat.  Appln.  KOKAI Publication No.  2007-60192 discloses an interpolation frame generation apparatus which detects a motion vector and generates an interpolation frame using it, thereby more clearly displaying a moving image. 
However, the technique disclosed in Jpn.  Pat.  Appln.  KOKAI Publication No.  2007-60192 always obtains a motion vector even when it is undetectable because of the motion of an image pattern.  If the detected motion vector is inaccurate, the image quality may degrade.