US-12625303-B2 - Head-up display system

US12625303B2US 12625303 B2US12625303 B2US 12625303B2US-12625303-B2

Abstract

A head-up display system including a polarizing optical engine and a first rotatable diffuser is provided. The polarizing optical engine is configured to provide a polarized image beam. The first rotatable diffuser is disposed on a path of the polarized image beam and configured to rotate when the polarized image beam passes through the first rotatable diffuser. The first rotatable diffuser is made of isotropic material, and the polarized image beam from the first rotatable diffuser obliquely strikes a windshield and is then reflected by the windshield to an eye of a user.

Inventors

Chi-Wen Lin

Assignees

HIMAX DISPLAY, INC.

Dates

Publication Date: 20260512
Application Date: 20230725

Claims (9)

1 . A head-up display system comprising: a polarizing optical engine configured to provide a polarized image beam; and a first rotatable diffuser disposed on a path of the polarized image beam and configured to rotate when the polarized image beam passes through the first rotatable diffuser, wherein the first rotatable diffuser is made of isotropic material, the polarized image beam from the first rotatable diffuser obliquely strikes a windshield and is then reflected by the windshield to an eye of a user, the first rotatable diffuser is disposed on a path of a first part of the polarized image beam, the head-up display system further comprises a second rotatable diffuser disposed on a path of a second part of the polarized image beam and configured to rotate when the second part of the polarized image beam passes through the second rotatable diffuser, the second rotatable diffuser is made of isotropic material, a distance between the first rotatable diffuser and the polarizing optical engine is different from a distance between the second rotatable diffuser and the polarizing optical engine, the path of the first part of the polarized image beam passes through the first rotatable diffuser without passing through the second rotatable diffuser, and the path of the second part of the polarized image beam passes through the second rotatable diffuser without passing through the first rotatable diffuser.
2 . The head-up display system according to claim 1 further comprising a curved mirror disposed on the path of the polarized image beam from the first rotatable diffuser and configured to reflect the polarized image beam from the first rotatable diffuser to the windshield.
3 . The head-up display system according to claim 2 , wherein the curved mirror is a freeform mirror.
4 . The head-up display system according to claim 1 , wherein the isotropic material of the first rotatable diffuser is glass having equal refractive indices in various directions.
5 . The head-up display system according to claim 4 , wherein the first rotatable diffuser has a diffusive surface.
6 . The head-up display system according to claim 5 , wherein the diffusive surface is a sand blasted surface.
7 . The head-up display system according to claim 1 , wherein a central ray of the polarized image beam traveling along an optical axis of the polarizing optical engine is incident on the windshield at an incident angle, wherein the incident angle is greater than or equal to a Brewster's angle of the windshield minus 10 degrees and is less than or equal to the Brewster's angle plus 10 degrees.
8 . The head-up display system according to claim 1 , wherein the first part of the polarized image beam forms a first image on the first rotatable diffuser, and the second part of the polarized image beam forms a second image on the second rotatable diffuser.
9 . The head-up display system according to claim 1 , wherein the polarized image beam forms an image on the first rotatable diffuser.

Description

BACKGROUND Technical Field The invention generally relates to a display system and, in particular, to a head-up display system. Description of Related Art A head-up display is a display that presents data without requiring users to look away from their usual viewpoints. A user of the head-up display is able to view information with the head positioned “up” and looking forward, instead of angled down looking at lower instruments. A head-up display also has the advantage that the user's eyes do not need to refocus to view the outside after looking at the optically nearer instruments. When a head-up display adopts a laser light source, the head-up display may also adopt a rotating diffuser disposed on the path of a laser beam emitted by the laser light source to reduce the speckle phenomenon due to the laser beam. However, in a conventional head-up display, the rotating diffuser is made of plastic material which has birefringence. When the laser beam passes through the rotating diffuser, the polarization direction of the laser beam is rotated continuously with the rotation of the rotating diffuser. The laser beam from the rotating diffuser obliquely strikes a windshield, and the windshield reflects the s-polarized light of the laser beam to the eyes of a user. The rotating polarization direction of the laser beam causes the intensity of the s-polarized light increases and decreases continuously. As a result, the user will see a flickering image. SUMMARY Accordingly, the invention is directed to a head-up display system, which is able to provide a stable image. An embodiment of the invention provides a head-up display system including a polarizing optical engine and a first rotatable diffuser. The polarizing optical engine is configured to provide a polarized image beam. The first rotatable diffuser is disposed on a path of the polarized image beam and configured to rotate when the polarized image beam passes through the first rotatable diffuser. The first rotatable diffuser is made of isotropic material, and the polarized image beam from the first rotatable diffuser obliquely strikes a windshield and is then reflected by the windshield to an eye of a user. In the head-up display system according to the embodiment of the invention, the first rotatable diffuser is made of isotropic material, so that when the first rotatable diffuser rotates, the polarization direction of the polarized image beam does not rotate with the rotation of the first rotatable diffuser. As a result, when the windshield reflects an s-polarized light of the polarized image beam to the eye of the user, the intensity of the s-polarized light does not vary with the rotation of the first rotatable diffuser, so that the head-up display system can provide a stable image and can reduce speckle phenomenon by the rotation of the first rotatable diffuser. To make the aforementioned more comprehensible, several embodiments accompanied with drawings are described in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. FIG. 1 is a schematic view of a head-up display system according to an embodiment of the invention. FIG. 2 is a schematic view of a head-up display system according to another embodiment of the invention. DESCRIPTION OF THE EMBODIMENTS FIG. 1 is a schematic view of a head-up display system according to an embodiment of the invention. Referring to FIG. 1, the head-up display system 100 in this embodiment includes a polarizing optical engine 200 and a first rotatable diffuser 110. The polarizing optical engine 200 is configured to provide a polarized image beam 202. In this embodiment, the polarizing optical engine 200 includes a laser source 210 and a light valve 220. The laser source 210 is configured to emit a laser beam 212. In this embodiment, the laser source 210 may include at least one laser diode. The light valve 220 is disposed on a path of the laser beam 212 and configured to convert the laser beam 212 into the polarized image beam 202. The light valve 202 is, for example, a liquid-crystal-on-silicon (LCOS) panel. In this embodiment, the LCOS panel may generate a holographic image. The first rotatable diffuser 110 is disposed on a path of the polarized image beam 202 and configured to rotate when the polarized image beam 202 passes through the first rotatable diffuser 110. In this embodiment, a rotation axis A1 of the first rotatable diffuser 110 is along the propagation direction of the polarized image beam 202. The first rotatable diffuser 110 is made of isotropic material. The isotropic material has equal refractive indices in various directions; that is, the isotropic material is not a birefringent material. In this e