The thickness of the unit is only 1cm.
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A screen of a TFT-LCD HUD
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Two TFT-LCD panels (left) and two passive LCD panels (right)
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Stanley Electric Co Ltd exhibited an automotive head-up display (HUD) that is only 1cm in thickness at Ceatec Japan 2016, which took place from Oct 4 to 7, 2016, at Makuhari Messe in Chiba City.

The HUD shows an image by reflecting an image of an LCD panel. There is not enough space on a dashboard. So, there is a high demand for slim HUD units.

According to Stanley Electric, HUD units of the same kind are generally thick because they use a direct-type backlight, which is placed on the reverse side of an LCD panel. Also, a high brightness is required for a backlight, sometimes making it necessary to use a heat sink for cooling.

To reduce the thickness of such HUD units, Stanley Electric employed a "side light type," which places the light source of a backlight near a side of an LCD panel. Though a side light type causes a shortage of brightness in general, the company solved the problem by using its proprietary prism sheet to increase light use efficiency, it said.

At Ceatec Japan 2016, Stanley Electric exhibited two types of HUDs. One uses a TFT-LCD panel, and the other uses a passive LCD panel (segment display). The TFT-LCD panel can display high-definition images while the passive LCD panel features a low cost and a high light use efficiency.