Head-up display

A head-up display for projecting a virtual image ahead of a windshield of a vehicle, comprising:

• a projector for projecting an image light;
• and
• a hologram lens having a diffraction equivalent to a hyperbolic-curve mirror along a line formed by intersection of the hologram lens and a vertical plane, an optical axis of said image light lying on said vertical plane, and a diffraction equivalent to a parabolic-curve mirror along a line formed by intersection of said hologram lens and a horizontal plane, said optical axis of said image light lying on said horizontal plane.

A head-up display for projecting a virtual image ahead of a windshield of a vehicle, comprising:

• a projector for projecting an image light;
• and
• a hologram lens having a diffraction equivalent to a parabolic-curve mirror which has a focal length f1 along a line formed by intersection of the hologram lens and a vertical plane, an optical axis of said image light lying on said vertical plane, and a diffraction equivalent to another parabolic-curve mirror which has a focal length f2 along a line formed by intersection of said hologram lens and a horizontal plane, said optical axis of said image light lying on said horizontal plane, said focal lengths f1 and f2 being formed so that virtual images focused by said vertical and horizontal parabolic-curve diffractions coincide with each other.

A head-up display for projecting a virtual image ahead of a windshield of a vehicle, comprising:

• a projector for projecting an image light;
• and
• a hologram lens having a diffraction equivalent to a hyperbolic-curve mirror along a line formed by intersection of the hologram lens and a vertical plane, an optical axis of said image light lying on said vertical plane, and a diffraction equivalent to an elliptic-curve mirror along a line formed by intersection of said hologram lens and a horizontal plane, said optical axis of said image light lying on said horizontal plane.