Backlight optical system for a multifocal light field hud

Abstract

This invention discloses a backlight optical system for a multi-focal-plane light field 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; a freeform lens for coupling the expanded light into the imaging optical system; and an image source located on one side of the freeform lens, the image source including a first focal plane usage area, a second focal plane usage area, a third focal plane usage area, and a fourth focal plane usage area. This invention achieves high uniformity illumination of multiple focal planes using only one backlight optical system, reducing cost and assembly difficulty, providing favorable conditions for the widespread adoption of multi-focal-plane HUDs. It is insensitive to the size ratio of different focal plane usage areas, allowing the ratio of different focal plane usage areas to be varied according to requirements without redesigning 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 multi-focal surface light field 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 multi-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 high uniformity of display and improve the comfort of HUD use. However, for multi-focal plane HUDs, multiple backlight optical systems are required for illumination. Multiple backlight optical systems increase the overall cost of HUDs, which is not conducive to the popularization of multi-focal plane light field 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 multi-focal surface light field HUDs. This system aims to solve the problem that existing multi-focal surface HUDs require multiple backlight optical systems for illumination, which increases the overall cost of the HUD and hinders its widespread adoption.

[0005] (2) Technical solution

[0006] To address the aforementioned technical problems, this utility model provides a backlight optical system for a multi-focal surface 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 image source is located on one side of the freeform lens and includes a first focal plane usage area, a second focal plane usage area, a third focal plane usage area, and a fourth focal plane usage area.

[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 sizes of the first focal plane usage area, the second focal plane usage area, the third focal plane usage area, and the fourth focal plane usage area can be changed through UI display.

[0016] Furthermore, when the angle between the imaging rays required by different focal planes and the image source normal is inconsistent, the freeform lens is transformed into an array lens to achieve this.

[0017] Furthermore, increasing the aperture of the lens and beam expander prism can increase the illumination area of ​​the entire image source.

[0018] Beneficial effects

[0019] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0020] The backlight optical system of this invention for multi-focal surface HUD can achieve high uniformity illumination of multiple focal surfaces using only one backlight optical system, saving space and cost, reducing costs and assembly difficulty, and providing favorable conditions for the popularization of multi-focal surface HUD; at the same time, the system is not sensitive to the size ratio of the area used by different focal surfaces, and the ratio of the area used by different focal surfaces can be changed according to needs without redesigning the backlight optical system. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the backlight optical system of the present invention used in a multi-focal surface light field HUD.

[0022] Figure 2 This is a schematic diagram of how the beam-expanding prism of this utility model expands collimated light rays.

[0023] Figure 3 This is a schematic diagram of the structure of the freeform surface lens of this utility model being transformed into an array lens.

[0024] Figure 4 This is a schematic diagram illustrating how the light-emitting aperture of the lens and beam expander prism is increased when the illumination area of ​​the entire image source is increased.

[0025] Figure 5This is a schematic diagram illustrating a specific application example of this utility model.

[0026] The labels in the attached diagram are as follows: 1. Light source; 2. Lens; 3. Beam expander prism; 4. Freeform lens; 5. Image source; 51. First focal plane area; 52. Second focal plane area; 53. Third focal plane area; 54. Fourth focal plane area. Detailed Implementation

[0027] This specific embodiment is a backlight optical system for a multi-focal surface light field HUD, and its structural schematic diagram is shown below. Figures 1-3 As shown, the system 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. The image source 5 is located on one side of the freeform lens 4. The image source 5 is arranged from left to right as follows: a first focal plane usage area 51, a second focal plane usage area 52, a third focal plane usage area 53, and a fourth focal plane usage area 54.

[0028] In this embodiment, lens 2 collimates the large-angle light emitted from light source 1 using total internal reflection, and collimates the small-angle light emitted from light source 1 using refraction. After collimation by lens 2, the directionality of the light beam is greatly improved, which facilitates subsequent control of the light by lens 2. Lens 2 collimates the large-angle light using total internal reflection without Fresnel loss, thus improving the utilization rate of light energy. The deflection of light by lens 2 satisfies Snell's law, which states that when light is obliquely incident from one medium into another, refraction occurs at the interface, and the sine of the incident angle is proportional to the sine of the refraction angle.

[0029] 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.

[0030] 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.

[0031] In this embodiment, the sizes of the first focal plane usage area 51, the second focal plane usage area 52, the third focal plane usage area 53, and the fourth focal plane usage area 54 are changed through UI display.

[0032] 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:

[0033]

[0034] 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.

[0035] In this embodiment, as Figure 3 As shown, once the imaging optical system is designed, if the angle between the imaging rays required by different focal planes and the normal of the image source 5 is inconsistent, this can be achieved by changing the freeform lens 4 into an array lens. That is, the lens tilt angle corresponding to different image source regions is changed. For example, the tilt angle corresponding to the first focal plane usage area 51 and the tilt angle corresponding to the second focal plane usage area 52 are inconsistent, so that the light rays are better coupled to the subsequent imaging system after being modulated by the freeform lens 4.

[0036] In this embodiment, as Figure 4 As shown, if it is necessary to increase the illumination area of ​​the entire image source 5, it can be achieved by redesigning the optical path to increase the light output aperture of the lens 2 and the light output aperture of the beam expander prism 3. The enlarged light output aperture needs to be consistent with the enlarged illumination area of ​​the image source 5 in order to meet the illumination requirements and achieve the highest possible energy utilization efficiency.

[0037] Specific application examples

[0038] like Figure 5 The figure shows a specific implementation example. When the area 52 of the second focal plane is increased, 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, so that the applicability of the backlight optical system is very good.

[0039] In summary, the backlight optical system for multi-focal surface HUD of this invention can achieve high uniformity illumination of multiple focal surfaces using only one backlight optical system, saving space and cost, reducing costs and assembly difficulty, and providing favorable conditions for the popularization of multi-focal surface HUDs; at the same time, the system is not sensitive to the size ratio of the area used by different focal surfaces, and the ratio of the area used by different focal surfaces can be changed according to needs without redesigning the backlight optical system.

[0040] All technical features in this embodiment can be freely combined according to actual needs.

[0041] 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 multi-focal surface HUD, characterized in that: 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; Image source (5), which is located on one side of freeform lens (4), includes a first focal plane usage area (51), a second focal plane usage area (52), a third focal plane usage area (53) and a fourth focal plane usage area (54).

2. The backlight optical system for a multifocal-plane light field HUD according to claim 1, wherein, 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 multifocal-plane light field HUD according to claim 1, wherein, 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 multi-focal surface HUD according to claim 1, characterized in that, The beam expander prism (3) expands the collimated light beam using a polarizing beam splitter.

5. The backlight optical system for a multifocal-plane light field HUD according to claim 1, wherein The sizes of the first focal plane usage area (51), the second focal plane usage area (52), the third focal plane usage area (53), and the fourth focal plane usage area (54) are changed through UI display.

6. The backlight optical system for a multi-focal surface HUD according to claim 1, characterized in that, When the angle between the imaging light required by different focal planes and the normal of the image source (5) is inconsistent, the freeform lens (4) is changed into an array lens to achieve this.

7. The backlight optical system for a multifocal-plane light field HUD according to claim 1, wherein Increasing the aperture of the lens (2) and the beam expander prism (3) can increase the illumination area of ​​the entire image source (5).

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