Head-up display device using a concave cylindrical lens for projecting image on screen

1. A head-up display device for projecting an image on a display screen comprising:

a liquid crystal display element for generating an original image;

a light source for emitting light toward the liquid crystal display element from a backside of the liquid crystal display element;

a reflection mirror for reflecting a light image of the original image passing through the liquid crystal display element and for projecting the light image as a projected image on the display screen; and

a concave cylindrical lens having a concave surface and disposed between the liquid crystal display element and the reflection mirror,

wherein the concave surface faces the reflection mirror,

wherein three-dimensional coordinates are defined in the concave cylindrical lens,

wherein the concave surface has a curved shape along with x axis of the three-dimensional coordinates,

wherein the concave surface extends along with y axis of the three-dimensional coordinates,

wherein the concave surface is configured to be rotated around the x axis so that z axis of the concave surface is tilted from an optical axis,

wherein the optical axis is defined to be directed from the light source to the reflection mirror,

wherein the head-up display device has a plurality of magnification ratios of the projected image with respect to the original image,

wherein the concave surface of the concave cylindrical lens has a curvature radius, which corresponds to the one of the magnification ratios,

wherein a view angle in the x axis is defined as a range of an angle of light, which is emitted with the angle in the x axis with respect to the optical axis from the light source as an original point toward the liquid crystal display element and has a predetermined intensity ratio with respect to straight light emitted along with the optical axis,

wherein a view angle in the y axis is defined as a range of an angle of light, which is emitted with the angle in the y axis with respect to the optical axis from the light source as an original point toward the liquid crystal display element and has a predetermined intensity ratio with respect to straight light emitted along with the optical axis,

wherein the view angle in the x axis is determined to be a view angle, which is necessary in the x axis for a case where the one of a plurality of magnification ratios is a minimum magnification ratio,

wherein the view angle in the y axis is determined to be a view angle, which is necessary in the y axis for a case where the one of a plurality of magnification ratios is a maximum magnification ratio, and

wherein the minimum magnification ratio of the view angle in the x axis corresponds to the maximum magnification ratio of the view angle in the y axis.

2. The head-up display device according to claim 1 ,

wherein the head-up display device is mounted on a vehicle,

wherein the display screen is a windshield of the vehicle, which is curved, and

wherein the reflection mirror has a reflection surface with a shape, which is determined to correct a distortion of the projected image attributed to a curvature of the windshield and the concave surface of the concave cylindrical lens.

3. The head-up display device according to claim 1 ,

wherein the head-up display device is mounted on a vehicle,

wherein the projected image has a length in a horizontal direction of the vehicle and a height in a vertical direction of the vehicle,

wherein the length of the projected image is larger than the height of the projected image, and

wherein the x axis of the concave cylindrical lens is in parallel to the horizontal direction of the vehicle.

4. The head-up display device according to claim 1 ,

wherein the concave cylindrical lens has an incident surface, which contacts a display surface of the liquid crystal display element,

wherein the light image of the original image transmitted through the liquid crystal display element is entered into the concave cylindrical lens via the incident surface, and

wherein the incident surface expands on a x-y plane.

5. The head-up display device according to claim 1 ,

wherein the head-up display device is mounted on a vehicle,

wherein the display screen is a windshield of the vehicle,

wherein the x axis of the concave cylindrical lens is in parallel to a latitudinal direction of the vehicle,

wherein the y axis of the concave cylindrical lens is tilted from a vertical direction of the vehicle, and

wherein the z axis of the concave cylindrical lens is tilted from a longitudinal direction of the vehicle.

6. The head-up display device according to claim 5 ,

wherein a rotation angle of the concave surface around the x axis is in a range between 10 degrees and 20 degrees.

7. The head-up display device according to claim 6 ,

wherein the concave surface along with y axis is not curved,

wherein the reflection mirror has a reflection surface with a shape, which is determined to correct a distortion of the projected image attributed to a curvature of the windshield and the concave surface of the concave cylindrical lens, and

wherein the reflection mirror is a concave mirror.

8. The head-up display device according to claim 7 ,

wherein the concave cylindrical lens has an incident surface, which contacts a display surface of the liquid crystal display element,

wherein the light image of the original image transmitted through the liquid crystal display element is entered into the concave cylindrical lens via the incident surface, and

wherein the incident surface is a flat surface expanding on a x-y plane.