VIDEO DISPLAY DEVICE
FIG4 is a diagram illustrating an example of a drive gradation table
In one or more embodiments, one frame is divided into N pieces of subframes, and on and off of the respective subframes are switched, whereby gradation display is performed. Note that the subframes are denoted by SF1, SF2... and SFN in order from a temporarily prior one. FIG4 shows an example of a drive gradation table, and longitudinal columns of the drive gradation table represent the gradations. The subframe data generator 12 generates the subframe data based on values in the drive gradation table, which correspond to the gradations of the video data. In the above, as shown in FIG4, an example is shown of the drive gradation table in which the subframes which turn on are sequentially increased from the temporarily posterior subframe toward the temporarily prior subframe as the gradation rises. However, the drive gradation table is not limited to this. The drive gradation table only needs to be a table in which a temporarily prior subframe is turned off at the time of a low gradation.
diagram
7
projection lens
5
PBS
12
subframe data generator
11
signal processor
1
visible light source
9
Gradation
4
illumination optical system
2
infrared light source
6
liquid crystal display element
10
signal synthesizer
3
dichroic mirror
['1. A video display device (100) comprising: a display element (6); a visible light source (1) configured to irradiate visible illumination light; an infrared light source (2) configured to irradiate infrared illumination light; a subframe data generator (12) configured to generate subframe data based on a mixed video signal in which a frame of a video signal for a visible light image and a frame of a video signal for an infrared light image are alternately repeated, the subframe data indicating on and off of an applied voltage to the display element (6) in the frames; a pixel circuit (13) configured to drive the display element (6) based on the subframe data generated by the subframe data generator (12); and a light source controller (14) configured to control on and off of the visible light source (1), wherein, when gradation of the mixed video signal is equal to or less than a predetermined gradation, the subframe data generator (12) generates the subframe data so that an applied voltage to the display element (6) is turned off during a first predetermined period from a start of the frame of the video signal for a visible light image or the video signal for an infrared light image, and wherein the light source controller (14) turns on the visible light source (1) after a lapse of a second predetermined period from a start of the frame of the video signal for a visible light image, and turns off the visible light source (1) at a  timing when the frame of the video signal for a visible light image is ended.']