Head-up display, a combiner used for the head-up display and a method of

Abstract

As a combiner, a hologram prepared by exposure to light is used wherein a combination of the central wavelength .lambda., the halfwidth .DELTA..lambda. and the diffraction efficiency .eta. of the diffraction spectrum of light minimizes the color difference between the color tone of light from a light source and the color tone in average of reflection light by the combiner, when observed by changing the angle, or the sum of the square of the color differences between the color tone of the light from the light source when observed by changing the angle and the color tone of the reflection light by the combiner. Then, the color tone of the light transmitting from the outside of a vehicle through the combiner, the light being observed by the driver of the vehicle, and the color tone of an outer light reflected by the combiner, the light being observed at the outside of the vehicle, approach a white color in comparison with use of a conventional combiner, whereby a transparent eyesight without any complementary color is given to the driver to thereby increase safety. Further, a head-up display which reduces a change of color even though an observer outside the vehicle looks at the combiner at any angular position and which gives a color tone near a white color, can be provided.