Backlight optical system for bifocal hud

Abstract

This invention discloses a backlight optical system for a dual-focal-area HUD, comprising: a light source for emitting light; a lens for collimating the light emitted from the light source; a beam expander prism for expanding the collimated incident light beam; a freeform lens for coupling the expanded light beam into an imaging optical system; and an image source, wherein the collimated light beam, after being expanded by the beam expander prism, is modulated by the freeform lens and coupled to the image source in a predetermined beam form. This invention achieves near-focus and far-focus illumination using only one backlight optical system, saving space and cost, and providing favorable conditions for the widespread adoption of HUDs. Furthermore, the system is insensitive to the size ratio of the near-focus and far-focus usage areas, allowing for adjustments to the ratio of the near-focus and far-focus usage areas as needed, without requiring a redesign of the backlight optical system.

Description

Technical Field

[0001] This utility model belongs to the field of HUD technology, specifically relating to a backlight optical system for a dual-focal-plane HUD. Background Technology

[0002] Most existing HUDs (Head-up Displays) only display information such as vehicle speed and navigation on a single focal plane with a fixed focal length. Because there is only a single focal plane at a fixed distance, prolonged use can lead to eye fatigue and dizziness. At the same time, the displayed image lacks a realistic sense of depth due to the single focal plane display. The development of HUDs will gradually transition to dual-focal-plane HUDs. Two focal planes at different distances can alleviate eye fatigue caused by prolonged use. This requires a matching backlight system for dual-focal-plane HUDs to achieve a highly uniform display and improve the comfort of using the HUD. However, dual-focal-plane HUDs require a separate backlight optical system for illumination. Two backlight optical systems will increase the overall cost of the HUD, which is not conducive to the popularization of dual-focal-plane HUDs. Utility Model Content

[0003] (1) Technical problems to be solved

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a backlight optical system for dual-focal-area HUDs, aiming to solve the problem that existing dual-focal-area HUDs require separate backlight optical systems for illumination, which increases the overall cost of the HUD and hinders its widespread adoption.

[0005] (2) Technical solution

[0006] To solve the above-mentioned technical problems, this utility model provides a backlight optical system for a dual-focal-plane HUD, comprising:

[0007] A light source, which is used to emit light;

[0008] A lens; the lens is used to collimate the light emitted from the light source;

[0009] A beam expander prism, which is used to expand collimated incident light rays;

[0010] A freeform lens, used to couple expanded light rays into an imaging optical system;

[0011] The collimated light rays from the image source, after being expanded by the beam expander prism, are modulated by the freeform lens and coupled onto the image source in a predetermined beam form.

[0012] Preferably, the light emitted by the light source includes large-angle light and small-angle light, and the lens collimates the large-angle light emitted by the light source using total internal reflection, and the lens collimates the small-angle light emitted by the light source using refraction.

[0013] Furthermore, the beam expander prism expands the collimated light beam using a semi-transparent, semi-reflective film.

[0014] Furthermore, the beam expander prism expands the collimated light beam using a polarizing beam splitter.

[0015] Furthermore, the image source includes a near-focus usage area and a far-focus usage area.

[0016] Furthermore, the sizes of the near-focus and far-focus usage areas can be adjusted via the UI display.

[0017] Beneficial effects

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] The backlight optical system for dual-focal-plane HUDs of this invention can achieve illumination for both near and far focal lengths using only one backlight optical system, saving space and cost and providing favorable conditions for the popularization of HUDs. At the same time, the system is not sensitive to the size ratio of the near-focal and far-focal usage areas, and the ratio of the near-focal and far-focal usage areas can be changed according to needs without redesigning the backlight optical system. Attached Figure Description

[0020] Fig. 1 This is a schematic diagram of the backlight optical system of the present invention used in a dual-focal-plane HUD.

[0021] Fig. 2 This is a schematic diagram of how the beam-expanding prism of this utility model expands collimated light rays.

[0022] Fig. 3 This is a schematic diagram illustrating a specific application example of this utility model.

[0023] The labels in the attached diagram are: 1. Light source; 2. Lens; 3. Beam expander prism; 4. Freeform lens; 5. Image source; 51. Near-focus area; 52. Far-focus area. Detailed Implementation

[0024] This specific embodiment is a backlight optical system for a dual-focal-plane HUD, and its structural schematic diagram is shown below. Figs. 1-3As shown, it includes a light source 1, a lens 2, a beam expander prism 3, a freeform lens 4, and an image source 5. The light source 1 is used to emit light; the lens 2 is used to collimate the light emitted by the light source 1; the beam expander prism 3 is used to expand the collimated incident light beam; the freeform lens 4 is used to couple the expanded light beam into the imaging optical system; the collimated light beam after being expanded by the beam expander prism 3 is modulated by the freeform lens 4 and coupled to the image source 5 in a predetermined beam form.

[0025] In this embodiment, the light emitted by the light source 1 includes large-angle light and small-angle light. The lens 2 collimates the large-angle light emitted by the light source 1 using total internal reflection, and the lens 2 collimates the small-angle light emitted by the light source 1 using refraction. After the light is collimated by the lens 2, the directionality of the light beam is greatly improved, which facilitates the subsequent control of the light by the lens 2. The lens 2 collimates the large-angle light using total internal reflection without Fresnel loss, which improves the utilization rate of light energy. The deflection of the light by the lens 2 satisfies Snell's law. Total internal reflection means that when light travels from an optically denser medium to an optically less dense medium, if the angle of incidence is greater than the critical angle, all the light will be reflected back to the optically denser medium without refraction.

[0026] In this embodiment, the beam expander prism 3 expands the collimated light beam using a semi-transparent and semi-reflective film. The light beam collimated by the lens 2 reaches the beam expander prism 3, which expands the collimated light beam to twice the original beam width using the semi-transparent and semi-reflective film, thus meeting the requirement of illuminating the image source area. The semi-transparent and semi-reflective film is a thin film attached to the beam expander prism 3, which realizes the beam expansion effect by allowing light to pass through and reflect light.

[0027] In some embodiments, the beam expander prism 3 can further expand the collimated light rays using a polarizing beam splitter. When the light rays collimated by the lens 2 reach the beam expander prism 3, the beam expander prism 3 will expand the collimated light rays using a polarizing beam splitter. The optical characteristics of the polarizing beam splitter are that P-light passes through and S-light is reflected. The polarizing beam splitter is a thin film attached to the beam expander prism 3 to achieve beam expansion.

[0028] In this embodiment, the image source 5 includes a near-focus usage area 51 and a far-focus usage area 52, and the size of the near-focus usage area 51 and the far-focus usage area 52 can be adjusted through the UI display.

[0029] In this embodiment, the collimated light beam after being expanded by the beam expander prism 3 is transmitted and modulated by the freeform lens 4. The light beam passing through the freeform lens 4 (i.e., beam modulation) needs to satisfy Snell's law and be coupled to the image source 5 in a predetermined beam form to achieve the requirement of uniform illumination across multiple focal planes. The expression for the freeform mirror 4 can be expressed using an XY polynomial:

[0030] ;

[0031] Where z is the vector height, C is the radius of curvature, k is a quadratic constant, and r is the radius vector. The coefficients of the polynomial, the first term The second term is the basis term for the freeform surface. As a freeform surface, it has a higher degree of freedom compared to traditional spherical and aspherical lenses, enabling precise control of light and achieving higher uniformity and energy utilization efficiency.

[0032] Specific application examples

[0033] like Fig. 3 The diagram shows a specific implementation example. When the near-focus area 51 is reduced, there is no need to change the backlight optical system. Only the display area distribution of the image source 5 needs to be changed through the UI display, which makes the backlight optical system very versatile.

[0034] In summary, the backlight optical system for dual-focal-area HUD of this invention can achieve illumination for both near and far focal lengths using only one backlight optical system, saving space and cost and providing favorable conditions for the popularization of HUDs. At the same time, the system is not sensitive to the size ratio of the near focal area 51 and the far focal area 52, and the ratio of the near focal area 51 and the far focal area 52 can be changed according to needs without redesigning the backlight optical system.

[0035] All technical features in this embodiment can be freely combined according to actual needs.

[0036] The above embodiments are preferred implementations of this utility model. In addition, this utility model can also be implemented in other ways. Any obvious substitutions without departing from the concept of this technical solution are within the protection scope of this utility model.

Claims

1. A backlight optical system for a dual focal plane HUD, characterized by: include: Light source (1), the light source (1) is used to emit light; Lens (2); the lens (2) is used to collimate the light emitted by the light source (1); Beam expander prism (3), which is used to expand the collimated incident light beam; A freeform lens (4) is used to couple expanded light rays into the imaging optical system; The collimated light rays from the image source (5), after being expanded by the beam expander prism (3), are modulated by the freeform lens (4) and coupled to the image source (5) in a predetermined beam form.

2. The backlight optical system for a dual focal plane HUD according to claim 1, characterized by, The light emitted by the light source (1) includes large-angle light and small-angle light. The lens (2) collimates the large-angle light emitted by the light source (1) using total internal reflection, and the lens (2) collimates the small-angle light emitted by the light source (1) using refraction.

3. The backlight optical system for a dual focal plane HUD according to claim 1, characterized by, The beam expander prism (3) expands the collimated light beam using a semi-transparent and semi-reflective film.

4. The backlight optical system for a dual focal plane HUD according to claim 1, characterized by, The beam expander prism (3) expands the collimated light beam using a polarizing beam splitter.

5. The backlight optical system for a dual focal plane HUD according to claim 1, characterized by, The image source (5) includes a near-focus usage area (51) and a far-focus usage area (52).

6. The backlight optical system for a dual focal plane HUD according to claim 5, characterized by, The sizes of the near-focus usage area (51) and the far-focus usage area (52) are adjusted via the UI display.

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