WO2020025648A1

WO2020025648A1 - Head-up display system

Info

Publication number: WO2020025648A1
Application number: PCT/EP2019/070563
Authority: WO
Inventors: Jianbo ZHAO; Jun Yuan TEY; Zi Xun ONG; Chong Dai; Xin Fang; Arne Jachens; Manikandan KALIMUTHU
Original assignee: Continental Automotive Gmbh
Priority date: 2018-07-31
Filing date: 2019-07-31
Publication date: 2020-02-06
Also published as: GB201820655D0; GB201817659D0; CN112470206B; GB2576064A; CN112470206A; GB2576060A; EP3830816A1

Abstract

The invention relates to a head-up display system for a motor vehicle, the system comprising: a screen; a display device; an arrangement of light sources configured to at least partially illuminate the screen, the illuminated screen configured to be cast on the display device; a controller configured to: determine which light source is to be illuminated, wherein the light source(s) to be illuminated corresponds to content to be displayed on the screen; calculate a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; drive each light source according to the calculated target illumination intensity. The invention further relates to a method of selectively controlling illumination intensity of each light source in an arrangement of light sources of a head- up display system, the method comprising: determining which light source is to be illuminated, wherein the light source(s) to be illuminated corresponds to content to be displayed on the screen; calculating a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; driving each light source according to the calculated target illumination intensity.

Description

Head-Up Display System

Field of invention

This invention relates to display systems, in particular head- up displays, applicable to the transportation industry.

Reference to Related Application

This application claims priority of UK application no. GB 1817659.4 (Attorney's docket no. 2018095607) and UK application no. UK application no. GB 1820655.7 (Attorney's docket no. 2018095607), both applications of which claims priority of SG application 10201806552Q with a date of filing of 31 July 2018, of which the aforesaid documents are collectively incorporated herein by reference in ist entirety.

Background of invention

Head-up displays are used in the automotive and aviation industries to allow a vehicle operator to view content in the operator's line of sight. The time that the operator's eyes need to be away from the travel path can therefore be reduced, which would otherwise be needed when viewing content from traditional display systems in the cockpit.

Since head-up displays typically project light depicting the content onto a vehicle windshield, designers of head-up displays typically use relatively high illumination intensities so that the content can clearly be seen by the operator. However, a large amount of power is required to enable such implementations. Furthermore, the heat generated from such implementations may typically be very high.

To minimize the power consumed and the heat generated, an existing implementation provides lighting elements of which their illumination intensities can be individually controlled to follow changing content. In the example of a movable pointer needle indicating vehicle speed, the lighting elements illuminating the pointer are controlled such that only the relevant lighting elements indicating the current speed are illuminated. That is, the lighting elements corresponding to a current speed are illuminated but are switched off when the speed changes, and the lighting elements corresponding to the new speed are illuminated.

However, the amount of content displayed on display systems is every increasing. This leads to a longer time needed to read and identify the information desired, even for displays in the operator's line of sight.

To mitigate this, existing implementations utilize colours to highlight critical content. However, coloured content usually does not have sufficient quality to provide the desired effect and impression.

There is therefore a need to provide a head-up display that overcomes or at least ameliorates one or more of the disadvantages discussed above.

Description

It is therefore an object to provide a head-up display system for a motor vehicle to address the problems discussed above. Particularly, it is an object to provide a display system which displays content in a manner that is efficiently received by the operator of the vehicle.

To accomplish these and other objects, there is provided, in a first aspect, a head-up display system for a motor vehicle, the system comprising: a screen; a display device; an arrangement of light sources configured to at least partially illuminate the screen, the illuminated screen configured to be cast on the display device; and a controller configured to: determine which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen; calculate a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; drive each light source according to the calculated target illumination intensity.

Advantageously, the disclosed system is capable of selectively controlling the illumination intensity of each light source in the arrangement, such that content in the focus area(s) are illuminated at a higher intensity than a non-focus area. Advantageously, preferential illumination of a focus area or a targeted area draws attention of the operator or driver of the vehicle to the focus area. Each light source is individually controlled, not only so that changing content may be illuminated accurately like in the prior art, but also that certain content may be selectively illuminated at higher intensity than others. Light source (s) may be turned off if not needed or if they correspond to an area on the screen that has no content. Advantageously, energy may be saved as not all light sources need to be lighted at all times when in use. In some implementations, the screen may be configured to display a plurality of contents, each content having a predefined priority level. The focus area may be configured to display content having a high priority level. For example, the focus area may advantageously display content that is important and/or critical to safety. Thus, prioritized content in the focus area may be selectively illuminated at higher intensity than others .

In a second aspect, there is provided a method of selectively controlling illumination intensity of each light source in an arrangement of light sources of a head-up display system, the method comprising: determining which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen; calculating a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; driving each light source according to the calculated target illumination intensity .

A controller such as one disclosed herein may execute the disclosed method. Advantageously, determining focus area(s) for preferential illumination provides the ability to draw attention of the operator or driver of the vehicle to the focus area (s ) .

The disclosed system and method provide a systematic way to identify the light sources that need to be operated or turned on. The disclosed system and method further provide an automated way to control the illumination intensity or brightness of the light sources so that a desired illumination intensity can be achieved. Advantageously, the disclosed system and method provides a user-centred design where there is minimal visual and cognitive distraction. The head-up display may be a human-machine interface configured to provide the driver with information that is easy and quick to understand to perform driving manoeuvres safely. Particularly, time taken to read content on the head-up display is reduced due to the highly illuminated content in the focus area(s) . Important content may be better enhanced or highlighted without the need for large computing power. Further, any uncertainty as to which displayed content is important may be reduced or eliminated.

Brief description of drawings

Fig. la shows an exploded view of picture generation unit 100 according to an embodiment of the present disclosure.

Fig. lb shows a cross-sectional view of picture generation unit 100.

Fig. lc shows an illustration of head-up display system 10 according to an embodiment of the present disclosure.

Fig. 2a shows an illustration of content displayed on screen 110 in segments.

Fig. 2b shows an illustration of the position of an arrangement of light sources 104 illuminating screen 110.

Fig. 3a shows an illustration of the illumination intensity percentage of the arrangement of light sources 104 illuminating screen 110. Fig. 3b shows an illustration of the displayed content on screen 110 illuminated by the arrangement of light sources 104 of Fig. 3a.

Fig. 3c shows an illustration of the displayed content on screen 110 illuminated by the arrangement of light sources 104 of Fig. 3a and with content in the non-focus area displayed in darker colour.

Fig. 4a shows an illustration of an outlined alert on screen 110, and the light source aligned with the alert is configured to blink.

Fig. 4b shows an illustration of a lighted halo around the content in the focus area, with the illumination intensity of the light source corresponding to the focus area being more intense than the rest of the areas.

Figs. 5a and 5b show an illustration of a focus area displaying turn-by-turn route guidance.

Fig. 6 shows an illustration of the electrical architecture of picture generation unit 100.

Fig. 7 shows a flow chart of the steps to obtain a target illumination intensity or an adjusted illumination intensity of each light source in an arrangement of light sources in accordance with an embodiment of the invention.

In the figures, like numerals denote like parts. Detailed description

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description of this invention will be provided for the purpose of explaining the principles of the invention and its practical application. The detailed description is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Modifications and equivalents will be apparent to practitioners skilled in this art and are encompassed within the spirit and scope of the appended claims .

In a first embodiment, there is provided a head-up display system for a motor vehicle. The head-up display system comprises a screen and a display device. The head-up display system further comprises an arrangement of light sources configured to at least partially illuminate the screen. The illuminated screen is configured to be cast on the display device. The head-up display system further comprises a controller configured to determine which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen. The controller is further configured to calculate a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area. The controller is further configured to drive each light source according to the calculated target illumination intensity. In other words, the controller is configured to selectively control the illumination intensity of each light source in the arrangement, such that one or more focus areas of the screen are illuminated at a higher intensity than a non-focus area.

A head-up display may also be referred to as a heads up display. The head-up display system may be coupled to, electronically connected to, or in electrical communication with a vehicle system, such as an instrument cluster in the cockpit of the vehicle, an advanced driving assistance system (ADAS) and/or an infotainment or navigation system. The head-up display system may be part of the vehicle system. The head-up display system may be configured as an output interface of the vehicle system, to output data from the vehicle system.

For example, the screen of the head-up display system may be configured to output the content of the instrument cluster, such as the gauges, telltale signs, etc, for the operator or driver of the vehicle to view. The screen may comprise a liquid crystal display (LCD) , a display comprising light emitting diodes (LED) , a display comprising thin-film transistors (TFT), combinations thereof, or any other suitable displays. In an example, the screen may comprise thin-film transistors. In another example, the screen may be a TFT-LCD screen. The instrument cluster may include another display disposed proximate the steering wheel or in the dashboard for direct viewing by the driver. The screen of the head-up display system may display the content, including images, graphics and/or information, to be cast on the display device. The screen may be the content source from which content is projected or reflected onto the display device. Therefore, a user looking at the screen may be able to see the same content as those cast on the display device.

In an implementation, the screen comprises a TFT-LCD display. The circuit layout of a TFT-LCD may be very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon, that is formed into a crystalline silicon wafer, they are made from a thin film of amorphous silicon that is deposited on a glass panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD process. Transistors take up only a small fraction of the area of each pixel and the rest of the silicon film is etched away to allow light to easily pass through it. Polycrystalline silicon is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or viewfinders. Amorphous silicon-based TFTs are by far the most common, due to their lower production cost, whereas polycrystalline silicon TFTs are also usable. The resolution of a screen according to the disclosure and the head-up display may be any suitable resolution, for example a 800 by 480 pixel resolution, a 480 by 240 pixel resolution, or even larger like a 1280 by 1024 pixel resolution, or a 426 by 149 pixel resolution of an active displayable area of the screen .

At least some parts of the screen or the whole screen may allow light to pass through. Light may be transmitted through the parts of the screen only where content is shown. The light source (s) corresponding to and illuminating these parts may be switched on, while the light source (s) corresponding to parts with no content may be switched off. The screen may be opaque at the parts where no content is shown to block light from passing through. Alternatively, at parts where no content is shown, the screen may be configured to absorb light or may display a dark or black background. The light sources provide a source of light or a backlight layer. One or some light sources or illumination areas of the backlight layer may be adapted to emit light to project only content of selected display areas, i.e. the focus areas, to the display device. When content is displayed on the screen, the parts of the screen with the content may transmit or let pass through a substantial amount of the light from the arrangement of light sources. The light transmitted may then be cast on the display device and reflected into the user's eye. Therefore, the user is able to see the content on the display device. On the other hand, at parts where light is blocked from passing through or is substantially absorbed, all or a substantial amount of the light is not cast on the display device and not reflected into the user's eye. These areas therefore appear dark to the user.

The display device may be a windshield of the vehicle or any surface or transparent display or an additional reflective disc (combiner disc) , on which the illuminated screen is cast upon or projected onto or reflected on. The display device receives light from the arrangement or array of light sources after passing through the screen. The illuminated content from the screen cast on the display device is then reflected into the driver' s eye such that the driver is able to see the illuminated content on the display device. The content cast on the display device may form the head-up display, which is a virtual display in the sense that the content, images and/or information from the screen that are cast on the display device are not static, but rather, are a projection or are floating on the display device. The content viewed from the display device may be a hologram. For example, the holographic content cast on the windshield forms the head-up display. At least part of the display device or head-up display may be located in the line of sight of the driver. The illuminated content may be cast on the display device or part of the display that is in the line of sight of the driver. Thus, the user or driver may advantageously not need to take his eyes away from the path of travel to look at the images or information on the screen but can view the same images or information in the line of sight on the head-up display or display device. As with holograms or projections, if the illumination is prevented from being cast on the display device, no images or information can be seen on the display device; if the illumination is partially prevented from being cast on the display device, the portion of the images or information prevented from being shown on the display device cannot be seen on the display device or the head-up display, but the portion of the images or information that is cast on the display device can be seen.

For display devices that are curved, such as a windshield, content rendered for display on the screen may need to be warped so that they are suitable for display on the display device. If the content or widget has to be warped for display on the display device, the warping properties of the widget may be predetermined by the manufacturer of the display system. Alternatively, the predetermined curve factor of the display device may be used to calculate the warping properties of the widget on-board, when the display system is in use. The different types of content or widgets that can be displayed are typically stored in a database in non-transitory storage media of the display system. For example, the physical qualities of a widget are stored in the database. The physical properties may include location of the widget when displayed on the screen, e.g. x- and y-coordinates of the screen, or the location of the widget when displayed on the display device after warping. The physical properties may include size of the widget, e.g. width and height, or the size of the widget when displayed on the display device after warping. The physical properties may include colour and transparency of the widget. The warping properties or factors to determine the warping properties, e.g. curve factor of the display device, may alternatively be stored in other non-transitory or transitory storage media of the display system for retrieval by the system when in use.

The arrangement of light sources is configured to at least partially illuminate the screen. The arrangement of the array of light sources and the screen is termed a "picture generation unit". Fig. la shows an exploded view of picture generation unit 100 according to an embodiment of the present disclosure. It is shown in Fig. la that the arrangement of light sources 104 illuminates the screen 110, providing a backlight to the screen 110. Screen 110 displays a black background with a representation of a speed limit thereon. Light from light source (s) 104 corresponding to the area of the screen 110 showing the black background may be absorbed by the black background or those light source (s) 104 may be switched off. Light source (s) 104 corresponding to the area of screen 110 showing the speed limit are switched on. In this area, a substantial amount of light is transmitted and passes through screen 110. Accordingly, each light source may be individually controlled so that only the desired content will be projected onto the display device. Appropriate light sources include light emitting diodes, thus the arrangement of light sources may comprise an arrangement of light emitting diodes. Other types of light sources, such as laser diodes, may be used. The arrangement of light sources 104 may be provided on a printed circuit board 102 and may therefore be termed as the "backlight layer". The PCB 102 may be connected to the controller (shown in Fig. la) . Light from the light sources may be refined before it illuminates the screen 110 to achieve the clarity, sharpness and luminance required of projected content. For example, the light may pass through one or more layers 106 comprising a collimator, diffusor, reflector, and/or polarizer. After passing through the screen 110, the light may be redirected onto the display device by a mirror system (see Fig. lc) . Fig. lb shows a cross-sectional view of picture generation unit 100. Light from the light sources 104 passes through collimator 106 which concentrates the light to travel towards screen 110. The collimated light passes through diffusor 106' which homogenizes the light so that light is not just seen as bright spots corresponding to each light source but is uniform.

Fig. lc shows an illustration of head-up display system 10 according to an embodiment of the present disclosure. Head-up display system 10 includes picture generation unit 100 and display device 16 which is a vehicle windshield in this embodiment. Light illuminating screen 110 may be directed by a mirror system and/or an imaging system 12, 14, so that the illuminated screen can be cast on display device 16. Light is then reflected off the display device 16 and into the user's eye .

The arrangement may comprise a plurality of light sources . The number of light sources may not be particularly limited and may be determined according to design requirements . A larger number of light sources for a given screen size means that more segments of the screen can be individually illuminated by each light source. This provides the ability to selectively illuminate individual pieces of content, rather than a whole area or segment. The light sources may be segmented or grouped to form an illumination area to correspond with an area of the screen, thereby providing the ability to selectively control the illumination area. Hence, the screen may be segmented into illumination areas, each illumination area corresponding to an area illuminated by each light source. On the other hand, a larger number of light sources gives rise to larger power requirements. Some considerations to determine the number of light sources in the matrix may include amount of content, number of segments on the screen allocated for content, power requirements, etc. For example, the position of each light source or the arrangement of light sources may correspond to the location of the content on the screen.

Each illumination area may be comprised of a plurality of pixels. Each illumination area may comprise an equal number of pixels. For example, for a 480 by 240 pixel size and an arrangement of 15 light sources, each illumination area may comprise 7680 pixels.

Exemplary content displayed on screen 110 is shown in Figs. 2a and 2b. The displayed content on the display device or head- up display may be substantially similar to the content displayed on the screen 110 shown in Figs. 2a and 2b. As shown in Fig. 2a, screen 110 includes eight segments 110a to llOh. Each or some segments display or can potentially display content. For example, segment 110b displays route guidance content from a navigation system (not shown) . Segment 110c displays speed limit content from the navigation system. Some of the segments may be configured to display direction- dependent content. For example, segments llOd and llOh can potentially display alerts to alert the driver of obstacles coming from the left (llOd) or the right (llOh) . Content in each segment need not be fixed. For example, segment 110b may display route guidance information in some instances and obstacle alerts in other instances. Content may alternatively be configured to be displayed on any part of the screen, not confined to segments.

Each light source 104 in the backlight layer 102 may be positioned at a position corresponding to or aligned with each segment of screen 110. Alternatively, as shown in Fig. 2b, the light sources may be arranged at regular intervals so that light rays can illuminate evenly across the screen. In Fig. 2b, the array of light sources 104a to 104o is arranged in a 3x5 matrix. Accordingly, in an example, light source 1041 illuminates segment llOe. Where segments lie across multiple light sources, the multiple light sources illuminate that segment. For example, segment 110c may be illuminated by light sources 104d, 104e, 104i and 104j .

Screen 110 may comprise a bezel 112. The bezel 112 is a border around the screen where no content is displayed. Bezel 112 may be opaque, thereby preventing light from the light sources 104 to pass through. Accordingly, it can be seen in Fig. 2b that the light sources along the edge of the screen 110 (104a to 104e, 104f and 104j to 104o) are partially obscured.

Light source (s) corresponding to segments of the screen that do not display content may be switched off or dimmed, or those segments of the screen may be configured to prevent light from passing through, thereby reducing power requirements or heat loss. Further advantageously, the number of light sources that need to be configured to control illumination intensity may be reduced .

The screen may be configured to display a plurality of contents. Content displayed may include navigation content, speed indication e.g. in the form of a graphical representation such as a speed scale or numerical representation, fuel or battery information e.g. in the form of a graphical representation such as a fuel gauge scale or a numerical representation such as a percentage of battery remaining or distance remaining, and ADAS information. The content may include turn-by-turn instructions, distance to the vehicle in front, and obstacle alerts. Graphical representations can also be termed as "icons" or "widgets". In view of the plurality of content provided to the driver for viewing on the head-up display, it may be advantageous to prioritize content that requires higher attention from the driver. Thus, each content may have a predefined priority level. Prioritized content may be enhanced to draw the driver's attention towards it. Prioritized content may be those that require a reaction from the driver, for example traffic sign warnings, to shorten the driver's reaction time to the corresponding road condition. Prioritized content may be those that are important and/or critical to safety. Content may be prioritized differently at different instances of time. For example, where a speed limit is detected for a road segment and the vehicle speed is above the speed limit, the speed limit content can be enhanced and/or highlighted. When an oncoming hazard is detected at a road segment with a speed limit, the hazard alert can be enhanced and/or highlighted in preference to the speed limit.

An area where high priority content is displayed may be determined to be a focus area, as opposed to a non-focus area which displays other contents. The focus area or display area corresponds to at least one light source or illumination area. The focus area may be configured to display content having a high priority level. The focus area may be operated at an enhanced level as compared to the non-focus area, to enhance the prioritized content as compared to other contents. For example, the focus area may be illuminated by the light source (s) illuminating the focus area at a higher intensity than the non-focus area to enhance the prioritized content. Increasing the illumination intensity of the focus area may include increasing the brightness of the focus area. Brightness may be defined by the unit candela per square meter (cd/m²) and may describe the brightness emitted by the light sources or the brightness of the content displayed on the display device. For different scenarios, there may be a maximum or a desired brightness of the light source or displayed content. In an example, the maximum desired brightness of the content displayed on the display device in bright daylight may be about 12500 cd/m², which will then be considered as a content brightness of 100%. In another example, the maximum brightness or luminance emitted by the light sources may be dependent on design requirements. The brightness of the light sources or content on the display device may be adjusted to a percentage of the maximum. That is, the illumination intensity of each light source may be adjusted to achieve content brightness varying between 100% and less than 100%, e.g. about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the maximum brightness. Alternatively, the illumination intensity of each light source may be adjusted from between 100% (i.e. the maximum luminance emitted by the light source) to less than 100%, e.g. about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the maximum luminance. In an example, the illumination intensity may be adjusted from between about 10% and 100% of the maximum luminance emitted by the arrangement of light sources . In this example, the focus area may be illuminated at 100% while the non-focus area may be illuminated at a different level, e.g. 10%. In another example, a focus area may be illuminated at 100%, a non-focus area adjacent to the focus area may be illuminated at 50% (i.e. dimmed to 50%), and other non-focus areas may be illuminated at 30% (i.e. dimmed to 30%) or switched off (i.e. 0%) . The non-focus area may be dimmed such that prioritized content in the focus area is displayed in a highlighting effect to the driver. The adjustment of illumination intensity may be undertaken by using pulse-width modulation to control the duty cycle of each light source or by controlling the current across each light source. Advantageously, increasing the illumination intensity of the focus area increases the brightness of the prioritized content, thereby increasing visibility of the prioritized content to the driver.

Enhancing the prioritized content may further include increasing the contrast between the focus area and the non focus area. The contrast may be achieved by local dimming, wherein the non-focus area or the content in the non-focus area is additionally toned down. For example, content in the focus area may be displayed in colour whereas content in the non-focus area may be displayed in greyscale to increase the contrast. Alternatively, content in the focus area may be displayed in any appropriate colour such as black, white, greyscale, colour or mixtures thereof, whereas content in the non-focus area may be displayed in greyer or darker colour or a colour that blends in with the background. Content in the non-focus area may be displayed with partial transparency. Content in the focus area may be displayed in a larger font or a larger size than content in the non-focus area. Modifying the content colour and size may be in addition to or an alternative to varying the illumination intensity between the focus area and the non-focus area. The colour and size of the content in the focus area may be suitably selected depending on the context of the content. For example, where the focus area includes the speed limit, the speed limit value may be encircled by a red circle to mimic an actual speed limit sign. Prioritized content may also be moved or displayed in the centre of the screen for better visibility.

Fig. 3 illustrates an example of controlling the illumination intensity of individual light sources to enhance prioritized content in the focus area. In the example of Fig. 3, a speed limit of 80 km/h is detected for the road segment, but the vehicle speed is 85 km/h, which is above the speed limit. The focus areas are therefore determined to be the speed limit and the vehicle speed information, while the rest of the area is determined to be the non-focus area. As shown in Fig. 2b, the speed limit graphic mainly lies across two light sources 104e and 104j . To enhance the speed limit graphic, as shown in Fig. 3a, the light source 104e mainly illuminating the speed limit graphic is operated at 100% and light source 104j is operated at 50%. The vehicle speed is also enhanced by illuminating light source 104m at 100%. The rest of the light sources are dimmed to 10%. The resulting display is shown in Fig. 3b, wherein the speed limit and the vehicle speed are enhanced or highlighted, as compared to the other content. As compared to Fig. 2b in which all light sources 104a to 104o are operated at 100%, the prioritized content of the speed limit and the vehicle speed are more visible to the driver. Furthermore, because the light sources aligned with the non-focus areas are dimmed to 10%, the lighted border surrounding the edge of the display, which is known as the "postcard effect" and can be seen in Fig. 2b, is substantially reduced in Fig. 3b.

In addition to controlling the illumination intensity of individual light sources to enhance prioritized content in the focus area, Fig. 3c illustrates an example of displaying content in the non-focus area in darker colour. The focus areas displaying the speed limit and vehicle speed information in Fig. 3c are now even more visible to the driver, as compared to Fig. 3b.

Alternatively or additionally, the focus area may be illuminated in pulses. The light source (s) illuminating the focus area may be configured to switch on and off, or between 100% and less than 100% e.g. between 100% and about 30%, to produce a blinking effect to the information displayed. The at least one light source or illumination area may emit light with a pre-determined periodically changing intensity, especially with a blinking intensity.

Alternatively or additionally, a lighted halo may be displayed around content in the focus area to create an outline or highlight or a 3D effect.

Fig. 4a illustrates an example of displaying an alert for a pedestrian coming from the left side. The alert's graphics are outlined and the light source aligned with the graphics is configured to blink. Fig. 4b illustrates another example of displaying a lighted halo around the content in the focus area, with the illumination intensity of the light source corresponding to the focus area being more intense than the rest of the areas.

Fig. 5a illustrates an example of a focus area displaying turn- by-turn route guidance. It can be seen that the first action is to go straight, while the next action is a left turn at a roundabout. Therefore, the illumination intensity of the light source corresponding to the straight arrow is higher than that of the roundabout. When the first action is completed and the roundabout is approaching, only the roundabout is shown and is illuminated more intensely than other content, as shown in Fig. 5b.

The brightness of the light sources may additionally be regulated according to ambient surrounding light. For example, when the ambient light is low, the brightness of the light sources may be regulated so that the screen and ultimately the head-up display is bright enough for viewing content but not too bright so as to hurt the user's eyes. The disclosed system may comprise a sensor, such as an ambient light sensor, to control, and in some embodiments automatically control, the brightness. Brightness in this scenario may be a global percentage change of the illumination intensity. For example, where the focus area is illuminated at 100% and the non-focus area is illuminated at 30%, automatic dimming of the light sources at low ambient light may cause illumination of the focus area to reduce to 80% and illumination of the non-focus area to reduce to 24%.

Other enhancements to the focus area are encompassed within the scope of the present disclosure. For example, the space between each content or graphics may be increased to prevent light from the illuminated areas from illuminating the adjacent, non-focus areas, thereby increasing the contrast between the focus and non-focus areas. Advantageously, the enhancing effects may be localized to the focus area. In another example, the level of back light emitted by the arrangement of light sources or the backlight layer is held constant, while the screen is adapted to create dynamic content or some form of highlighted content through the usage of colours .

The illumination intensity of each light source may be selectively controlled by a controller. An illustration of the electrical architecture of picture generation unit 100 comprising controller 120 is shown in Fig. 6. The controller 120 may comprise a power supply unit 122 configured to provide voltage and current to the arrangement of light sources 104 on printed circuit board 102. The power supply unit 122 may comprise a voltage booster 124 to provide sufficient voltage to power all the light sources 104 where necessary. The power supply unit 122 may comprise a two-channel current regulator 126-1 and 126-2. Current regulator 126-1 and 126-2 provides a constant current to the light sources 104 regardless of any change in voltage load. The voltage load changes depending on the number of light sources that are powered. In the embodiment of Fig. 6 of a 3x5 LED matrix, the current of 8 LEDs (104-1) can be regulated by current regulator 126-1, while the current of the remaining 7 LEDs (104-2) can be regulated by current regulator 126-2. The controller 120 may comprise light source driver or manager 128 to implement the activation, deactivation, dimming, decreasing and increasing of the illumination intensity of each light source 104. The controller 120 may be adapted to control each light source 104 so that the illumination intensity and illumination segments can be turned on or off or dimmed at pre-determined instances. The controller 120 may be adapted to turn off one or some of the light sources 104 corresponding to a non-focus area, so that unnecessary artefacts are avoided. The light source driver 128 may implement the luminance adjustment of each light source by pulse-width modulation. As is known in the art of pulse width modulation, increasing the duty cycle increases the amount of time that power to the light source is provided. The light source driver 128 may comprise circuitry 128-1 and 128-2, connecting current regulator 126-1 and 126-2 respectively, to light sources 104-1 and 104-2 respectively. Circuitry 128-1 and 128-2 may comprise typical components such as resistors, transistors, diodes, etc, which can be controlled to provide the selective control and customizability of each light source afforded by the disclosure. Each light source may be associated with one or more components in circuitry 128-1 and 128-2 in order to provide the individual activation, deactivation and dimming of each light source. The light sources 104-1 and 104- 2 may be connected to the respective driver 128-1 and 128-2 either in parallel, in series, or a combination, e.g. a chain of light sources on each parallel chain. The controller 120 of Fig. 6 is exemplary and the controller provided in the present disclosure may comprise other components not in controller 120, more components or less components than controller 120. The light source driver 128 may drive each light source 104 corresponding to the focus or non-focus areas to emit light with a pre-determined intensity, which may be determined by logic, software or machine-readable instructions. Therefore, the controller 120 may further comprise logic, software or machine-readable instructions to selectively control the illumination intensity of each light source. The machine- readable instructions may reside in various types of storage media, for example a storage medium (not shown) on a circuit board 130 also comprising one or more processors (not shown) to carry out the instructions. The circuit board 130 comprising the processor (s) and storage media may be a general computing unit or an electronic control unit of the head-up display system or, if the head-up display system is part of another vehicle system such as the instrument cluster, the circuit board 130 may be incorporated in an electronic control unit of the other vehicle system. Circuit board 130 is capable of determining the content to be output onto the screen 110. For example, circuit board 130 may receive navigation instructions from a navigation system (not shown) and may render content and control the arrangement of the rendered content to be output to the screen 110. The circuit board 130 may be electrically connected to the controller 120 or the light source driver 128 via a serial communication bus 129, e.g. UART or SPI . The one or more processors, upon reading the instructions, may instruct the controller 120 or driver 128 to implement the actions. The circuit board 130 housing the main components of the disclosed system may be connected to, or in electrical communication with, the screen 110 arranged in alignment or juxtaposition with the circuit board 102 comprising the light sources 104. The circuit board 130 may be connected to other vehicle systems by main connector 132. The circuit board 130 may be connected to other typical components 134, such as a stepper motor. The controller 120 may be configured to determine which light source is to be illuminated, operated or turned on. The light source (s) to be illuminated corresponds to content to be displayed on the screen. Logic to determine an on/off matrix may be comprised in a content scanning unit. Individual widgets may be rendered and may be eventually combined or juxtaposed to obtain a surface or frame for display on the screen. The frame data may be written into a hardware buffer. The content scanning unit may scan each pixel in the hardware buffer to determine whether that pixel is to display content. Each pixel may comprise data values for the primary colours, red, green and blue, and optionally other colours like yellow. A value of 0 means the pixel does not show any colour and therefore does not show any content, while a maximum R, G or B value, e.g. 255, represents full coloured content. Each pixel may also comprise data values for transparency, whereby a value of 0 means that the pixel is not transparent, and content is therefore displayed. The machine-readable instructions may dictate that the data values of each pixel are read, and calculations are made to determine if the values are above a threshold value. If so, it is determined that the pixel is to display content. In another implementation, alternate rows and/or columns of pixels are scanned, which may advantageously reduce the time taken for this step. Thus, the controller 120 may be configured to determine a colour value of pixels to be displayed on the screen, wherein content is to be displayed on the screen when the determined colour value is above a threshold colour value. The threshold colour value is up to the requirements of the display system. For example, the threshold colour value may be more than 20%, more than 25%, more than 30%, more than 40%, of the maximum value, e.g. 25% of the maximum value. In yet another implementation, instead of determining the colour value of the pixels in the hardware buffer, the content scanning unit may retrieve the properties of the content or widgets to be displayed from memory to determine the location and size of the content to be displayed, and thereby determine the respective light source for that location to be turned on. Where an illumination area is not completely or substantially completely utilized to display a widget, the respective pixels for that location and size of widget are determined for the next step.

Next, as a plurality of pixels make up an illumination area, it may not be efficient to illuminate a light source if a small number of pixels within the illumination area displays content. Moreover, light from neighbouring light sources may be sufficient to illuminate these pixels. This scenario may occur when part of a widget encroaches onto another illumination area. Fig. 2b illustrates this scenario whereby the speed limit widget is displayed mostly on illumination areas 104e and 104j and partly on illumination areas 104d and 104i. Therefore, the number of pixels that are determined to display content may be calculated as a percentage of the total number of pixels in that illumination area. If the percentage calculated is more than a threshold percentage, that is, if the number of pixels displaying content in an illumination area is more than a threshold number, it may then be determined that the light source corresponding to that illumination area is illuminated or turned on. The threshold percentage is up to the requirements of the display system. For example, the threshold percentage may be more than 1%, more than 2%, more than 5%, more than 10%, of the total number of pixels in the illumination area, e.g. 2.5%. The on/off matrix may be populated accordingly to determine which light source is to be illuminated, the light source (s) to be illuminated corresponding to content to be displayed on the screen. The on/off matrix may be written onto transitory storage media for the controller 120 or driver 128 to implement the actions .

Additionally, or concurrent to the determination of which light sources should be turned on or off, the controller 120 may be configured to determine a brightness of the environment surrounding the display device. As mentioned above, the brightness of the light sources may be regulated according to ambient surrounding light. Logic to determine the general brightness of the light sources, termed as global brightness or conversely global dimming, may be comprised in a global dimming unit. The global dimming unit may analyse sensor data, e.g. data from the ambient light sensor, to determine a global percentage change of the illumination intensity of the light source (s) to be turned on. The global percentage change may cause the target illumination intensity of the light sources to be increased or decreased by the same amount.

The controller 120 may be configured to calculate a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area. Logic to determine the target illumination intensity of a light source may be comprised in a local dimming unit. The local dimming unit may retrieve the priority levels of each content to be displayed from the hardware buffer or other database, or may calculate the priority levels of each content based on the frame data in the hardware buffer. As mentioned above, if an illumination area is a focus area comprising prioritized content, the illumination area may be illuminated at a higher intensity and therefore the light source illuminating that illumination area may have a higher target illumination intensity than other light sources . The local dimming unit may retrieve the on/off matrix from the content scanning unit to determine the target illumination intensity of the light sources that are to be turned on. The local dimming unit may receive information, such as the global percentage change, from the global dimming unit. The local dimming unit may therefore analyse the on/off array, populate the priority levels or highlight factor of illumination areas which are focus areas to arrive at a target illumination intensity, and apply a percentage increase or decrease of the target illumination intensity based on the ambient brightness. Although described in this sequence, the steps need not be performed in the same sequence or may be omitted if not required .

Light from neighbouring light sources contribute to the overall brightness of the illuminated content. However oftentimes, this is not considered when setting an illumination intensity for a light source. Accordingly, the controller 120 may be configured to adjust an individual illumination intensity of a light source based on the target illumination intensity of its neighbouring light sources, such that the target illumination intensity of the light source is met. Logic to determine the adjustment of the illumination intensity based on light coming from neighbouring light sources may be comprised in a compensation unit. The adjustment may be executed according to the following formula:

wherein : i refers to the first, second, third, ..., or the last n^th light source in the arrangement, which for example may be 104a, 104b, ..., or 104o as shown in Fig. 2b;

I refers to the target illumination intensity for light source i, which is received from the local dimming unit;

a refers to a curve factor of the display device specific for the light source i;

S refers to the individual illumination intensity of light source i, which is to be determined by the compensation unit; f refers to the contribution factor of a neighbouring light source, N refers to the brightness or illumination intensity of the neighbouring light source, and f and N are calculated for each neighbouring light source of light source i and summed .

As reflected by the formula above, the individual illumination intensity S considers the curve factor a of the display device specific for the light source i. For example, when the part of the screen illuminated by light source i is cast on the corresponding part of the display device, the curve factor a of that part of the display device is obtained, e.g. from a database in the non-transitory storage media or a buffer. Curve factors are unique to head-up display systems.

The contribution factor f of a neighbouring light source is dependent on the properties of each picture generation unit. For example, a particular lightguide incorporated into a picture generation unit (not shown in Fig. lb), which is used to guide the light from the light source, may affect how light from a neighbouring light source encroaches into an illumination area. As the construction of a lightguide differs from PGU to PGU, contribution factor f therefore varies from PGU to PGU. It may be obtained by determining the brightness value in cd/m² of the light source i when light source i is switched off while the neighbouring light source is switched on. The illumination intensity of the neighbouring light source N may be the target illumination intensity obtained from the local dimming unit for this neighbouring light source or the S value if already determined by the compensation unit.

S may then be obtained for each light source sequentially. As the calculated S value may be input as the N value for the next light source, the S value calculations for each light source may be iterated until the S value for each light source converges to a steady value.

Advantageously, the adjusted individual illumination intensity fine-tunes or calibrates the target illumination intensity so that the current provided to the light source is on point, thereby saving energy and reducing energy losses. Further advantageously, if there are more than one focus areas, the compensation unit allows for the focus areas to have similar brightness levels within an acceptable tolerance across the entire screen. Therefore, the present disclosure allows for the brightness levels of the displayed content to be homogeneous. Advantageously, the actual brightness levels of the displayed content may correspond to and achieve the calculated target illumination intensity in an illumination area, regardless of whether neighbouring light sources or neighbouring illumination areas affect its actual brightness level .

The controller may then be configured to drive each light source according to the calculated target illumination intensity or the adjusted individual illumination intensity. Particularly, the calculated target illumination intensity or the adjusted individual illumination intensity may be converted into pulse width modulation (PWM) values to drive the light sources as described above.

The content scanning unit, the global dimming unit, the local dimming unit and the compensation unit may be discrete logic or software packages and/or may be part of machine-readable instructions governing operation of the head-up display system. Two or more units may be combined into one discrete software package. If a head-up display system does not require the functions of any of the units, that unit may be omitted. For example, the controller may be configured to: determine which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen; calculate a target illumination intensity of each light source to be illuminated based on the target illumination intensity of its neighbouring light sources; and drive each light source according to the calculated target illumination intensity.

Fig. 7 shows a flow chart of the steps to obtain a target illumination intensity or an adjusted illumination intensity of each light source in an arrangement of light sources in accordance with an embodiment of the invention. Step 202 represents the step of determining which light source is to be illuminated. As mentioned above, an on/off matrix may be populated by analysing where the content is to be displayed and the light source (s) corresponding to the location and size of the content that should be switched on. Step 204 represents the step of determining the brightness of the environment surrounding the display device, so that content projected on the display device is projected at an appropriate illumination intensity. Step 204 may comprise the global dimming unit. Step 204 may comprise retrieving environmental brightness data from a storage medium, such as from the memory of a sensor measuring environmental brightness. Brightness of the environment may translate into a global percentage change of the illumination intensity of the light source (s) to be turned on. The global percentage change and the matrix of which light sources are switched on or off are fed into step 206, which represents the step of calculating a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area. Step 206 may comprise the local dimming unit. Step 206 takes into account the priority levels of each content to be displayed to obtain a target illumination intensity. The target illumination intensity of each light source is fed into step 208, which represents the step of adjusting the target illumination intensity to account for illumination from neighbouring light sources, thereby obtaining an individual illumination intensity of that light source. Step 208 may comprise the compensation unit. In step 210, PWM values are then calculated based on the individual illumination intensities determined for each individual light source. In step 212, the PWM values are then communicated to the respective drivers (128-1 or 128-2 as shown in Fig. 6) to drive the light sources (104-1 or 104-2 in Fig. 6) .

In a second embodiment, there is provided a method of selectively controlling illumination intensity of each light source in an arrangement of light sources of a head-up display system. The method comprises determining which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen. The screen is configured to be at least partially illuminated by an arrangement of light sources such as one disclosed herein. The method further comprises calculating a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area. Each light source is then driven according to the calculated target illumination intensity.

The method may further comprise displaying a plurality of contents on the screen. The screen may be configured to display a plurality of contents to allow the driver to view content on the display device or head-up display, as described above. Each content may have a predefined priority level, wherein content having a high priority level is displayed in the focus area on the screen. The priority level of each content may be predetermined and stored in storage media or memory of the head-up display system. The priority level of contents that are important and/or critical to safety may be higher than, for example, that of content providing information such as vehicle speed. The priority level of each content may be different at different instances of time, as described herein. Each content may have a priority score for different scenarios. A scenario may allocate the same priority score for more than one content, such as the example illustrated in Fig. 3.

Thus, determining the focus area may comprise calculating the priority score of each content for each scenario. The focus area which displays content having a high priority level and/or a high priority score is illuminated more intensely or enhanced as compared to other content to advantageously draw the driver's attention towards it.

Illuminating the focus area at a higher intensity compared to the non-focus area may comprise adjusting the luminance value of the light source (s) illuminating the focus area to a higher value and/or adjusting the luminance value of the light source (s) illuminating the non-focus area to a lower value. The luminance value may be a percentage of the maximum luminance value of each light source. The controller may undertake the adjustment of luminance or illumination intensity by pulse width modulation, specifically by controlling the duty cycle current across each light source.

To determine which light source is to be illuminated or switched on, the method may further comprise determining a colour value of pixels to be displayed on the screen, wherein content is to be displayed on the screen when the determined colour value is above a threshold colour value. The pixels in a hardware buffer may be scanned to determine a colour value and a percentage of the determined colour value against the maximum colour value is determined. Alternatively, to determine which light source is to be illuminated or switched on, the method may further comprise obtaining the location and size of the content to be displayed from memory.

Where content is displayed across several illumination areas, the method may further comprise determining a percentage of the illumination area that is to display content. When the determined percentage is more than a threshold percentage, that light source is illuminated.

As light from neighbouring light sources contribute to the overall brightness of the illuminated content, the disclosed method provides for adjusting an individual illumination intensity of a light source based on the target illumination intensity of its neighbouring light sources, such that the target illumination intensity of the light source is met. Determination of the adjustment may be carried out as disclosed above. For example, the adjustment may further comprise determining a curve factor of the display device. Taking the curve factor of the display device into account is advantageous since light may be reflected off curved surfaces differently. Hence, it is advantageous that the disclosed method considers the curve factor to modify the individual illumination intensity or the target illumination intensity appropriately.

The target illumination intensity may further consider ambient light. Thus, the method may further comprise determining a brightness of the environment surrounding a display device of the head-up display system.

If a head-up display system does not require the functions of any of the steps, that step may be omitted. For example, the method may comprise: determining which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen; calculating a target illumination intensity of each light source to be illuminated based on the target illumination intensity of its neighbouring light sources; and driving each light source according to the calculated target illumination intensity .

To operate the focus area at a further enhanced level as compared to the non-focus area, the method may comprise further enhancing the content and/or the illumination. For example, the method may comprise controlling the light source (s) illuminating the one or more focus areas to illuminate in pulses. The light source (s) illuminating the focus area may be controlled to switch on and off, or between 100% and less than 100% e.g. between 100% and about 30%, to produce a blinking effect to the information displayed. Additionally or alternatively, the method may comprise dimming the light source (s) illuminating the non-focus area, e.g. to less than 100% for example 30%. Additionally or alternatively, the method may comprise switching off the light source (s) corresponding to the non-focus area. Additionally or alternatively, the method may comprise displaying the content in the non-focus area in greyscale. Other enhancements to the content and/or illumination of the focus area or increasing the contrast between the focus and non-focus areas are described above.

The disclosed method may be implemented in a typical computer hardware configuration, which may be incorporated into the vehicle. The disclosed method may be a computer-implemented method for performing at least certain steps in the method. The method may be implemented, for example, by operating a computer, as embodied by an electronic control unit, to execute a sequence of machine-readable instructions to perform the method. Thus, the disclosure may include a programmed product residing on storage media (or a storage device) tangibly embodying a program of machine-readable instructions executable by an electronic control unit to perform the above method .

Claims

Patent claims

1. A head-up display system for a motor vehicle, the system comprising :

a screen;

a display device;

an arrangement of light sources configured to at least partially illuminate the screen, the illuminated screen configured to be cast on the display device;

a controller configured to:

determine which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen;

calculate a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; drive each light source according to the calculated target illumination intensity.

2. The system of claim 1, wherein the controller is further configured to: adjust an individual illumination intensity of a light source based on the target illumination intensity of its neighbouring light sources, such that the target illumination intensity of the light source is met.

3. The system of claim 1 or 2, wherein the target illumination intensity is further based on a brightness of the environment surrounding the display device.

4. The system of claim 2 or 3, wherein the individual illumination intensity is further based on a curve factor of the display device.

5. The system of any preceding claim, wherein the controller is further configured to: determine a colour value of pixels to be displayed on the screen, wherein content is to be displayed on the screen when the determined colour value is above a threshold colour value.

6. The system of any preceding claim, wherein the screen is segmented into illumination areas, each illumination area corresponding to an area illuminated by each light source .

7. The system of claim 6, wherein the controller is further configured to: determine a percentage of the illumination area that is to display content, wherein the corresponding light source is illuminated when the determined percentage is more than a threshold percentage .

8. The system of any preceding claim, wherein the controller controls the illumination intensity by controlling duty cycle of each light source.

9. The system of any preceding claim, wherein the arrangement of light sources comprises an arrangement of light emitting diodes .

10. The system of any preceding claim, wherein the screen comprises thin-film transistors.

11. A method of selectively controlling illumination intensity of each light source in an arrangement of light sources of a head-up display system, the method comprising : determining which light source is to be illuminated, wherein the light source (s) to be illuminated corresponds to content to be displayed on the screen;

calculating a target illumination intensity of each light source to be illuminated, such that content in one or more focus areas of the screen have a higher target illumination intensity than content in a non-focus area; driving each light source according to the calculated target illumination intensity.

12. The method of claim 11, further comprising adjusting an individual illumination intensity of a light source based on the target illumination intensity of its neighbouring light sources, such that the target illumination intensity of the light source is met.

13. The method of claim 11 or 12, wherein calculation of the target illumination intensity further comprises determining a brightness of the environment surrounding a display device of the head-up display system.

14. The method of claim 12 or 13, wherein adjustment of the individual illumination intensity further comprises determining a curve factor of the display device.

15. The method of any one of claims 11-14, further comprising determining a colour value of pixels to be displayed on the screen, wherein content is to be displayed on the screen when the determined colour value is above a threshold colour value.

16. The method of any one of claims 11-15, further comprising, where the screen is segmented into illumination areas, each illumination area corresponding to an area illuminated by each light source, determining a percentage of the illumination area that is to display content, wherein the corresponding light source is illuminated when the determined percentage is more than a threshold percentage.