| 摘要 |
PROBLEM TO BE SOLVED: To suppress the unnecessary diffraction by the sunbeams, to prevent the missing of a part of displayed information and to lessen the attenuation of light in optical paths without allowing the display to be shielded by the presence of objects by irradiating a hologram with this information while totally reflecting the information in a windshield at an incident angle of a specific range. SOLUTION: In the case of the windshield of a sandwich type formed by adhering two sheets of sheet glass 2, 2' with intermediate films 3, 3', the light progresses in the windshield while totally reflecting therein when the thickness of the sheet glass 2, 2' is defined as t1 (mm), t2 (mm), the size of the hologram 1 is defined as 1'(mm) and the display information from a display 4 is made incident at the incident angleθon the inside of the windshield via a prism 5. The display information is made incident as an+1 , bn+1 on the hologram 1 and is diffracted by the hologram. The information is made visible to the eyes 6 of a driver, etc. At this time, the incident angleθis so set as to satisfy the conditions tan<-1> [1/ 2(t1 +t2 )}]<=θwhen the length at which the display information is projected to the boundary of the windshield is defined as 1(mm).
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