| 摘要 |
PURPOSE:To correct the chromatic aberration by allowing the white light from a light emitting body to be made incident temporarily on a reflecting hologram plate, diffracting and reflecting it, and placing its diffracted light in an angle relation for leading it to a hologram plate for information. CONSTITUTION:Components of green and red of white light are diffracted and reflected by first and second hologram plates 23, 34 respectively, and led to a hologram plate 30 for scale and a pointer hologram plate 35, and by the hologram plates 30, 35, a green scale and a red pointer are reproduced as virtual images, and a driver recognizes a speedometer by the virtual image. In this case, when parallel rays are diffracted and reflected by the first hologram plate 23, they are reflected to different directions, based on a wavelength dispersion characteristic of a diffraction phenomenon. However, when the diffracted and reflected light is made incident on the hologram plate 30 for scale, the wavelength dispersion characteristic by the first hologram plate 23 and the wavelength dispersion characteristic by the hologram plate 30 for scale negate each other. In such a way, as for the emitted light from the hologram plate for scale its chromatic aberration is corrected.
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