WO2002035276A1

WO2002035276A1 - A head-up display for a motor vehicle

Info

Publication number: WO2002035276A1
Application number: PCT/SE2001/002272
Authority: WO
Inventors: Jan-Erik KÄLLHAMMER
Original assignee: Autoliv Development Ab
Priority date: 2000-10-26
Filing date: 2001-10-18
Publication date: 2002-05-02
Also published as: GB2368403B; AU2001296156A1; GB2368403A; GB0026222D0

Abstract

In a head-up display for a motor vehicle, a combiner (9) is provided mounted on the windscreen (10) of the vehicle. The combiner enables an optical combination to be produced which is a combination of an image viewed through the windscreen and an image projected on to the combiner. The combiner (9) comprises at least one region (14) in which the optical transmission characteristic of the combiner may be adjusted. Control means (15) are provided to adjust the optical transmission characteristics of the region.

Description

^ςA HEAD-UP DISPLAY FOR A MOTOR VEHICLE"

THE PRESENT INVENTION relates to a head-up display for a motor vehicle.

Previously it has been proposed (see US-A-5,414,439) to use a head-up display in a motor vehicle wherein an image or images are projected onto a combiner incorporated in the windscreen of the vehicle, which is in the field of view of the driver of the vehicle. The projected image is displayed on the combiner at a distance in front of the driver of the vehicle, and in his line of sight such that the driver of the vehicle may view the image while also viewing the road in front of the vehicle.

One problem that can arise with the previously proposed arrangement is that, during bright daylight conditions when the driver of the vehicle may be subjected to high exterior ambient light level or "glare", the combiner may appear to be substantially transparent and any head-up images transmitted therethrough may be difficult to distinguish, from the high ambient light level or "glare" by the occupant of the vehicle. Ideally, a combiner should enable the projected image to be seen, regardless of the conditions outside the vehicle, and should also provide at least an adequate image of the road when required. The present invention seeks to provide an improved head-up display for a motor vehicle.

According to the present invention there is provided a head-up display for a motor vehicle, the head-up display comprising a combiner adapted to be mounted in the field of view of a driver of the vehicle, an image generator arrangement to generate an image and to transmit the image onto the combiner, the combiner comprising at least one region wherein the optical transmission characteristic of the combiner may be adjusted, control means being provided to adjust the optical transmission characteristic of the region.

Conveniently, the image generator arrangement is a projector.

Preferably, the combiner comprises two said regions.

Conveniently, one of said regions is substantially smaller than the other said region.

Preferably, the optical tiansmission characteristic of the two regions are independently adjustable.

Conveniently, a light detector is provided adapted to detect ambient light conditions on the exterior of the vehicle and to provide a signal to the control means, the control means controlling the optical tiansmission characteristic of at least one said region in response to said signals. Piefeiably, the head-up display furthei comprising a cameia, the camera being adapted to send signals lepiesentative of an image to the image geneiator aπangement

Advantageously, the cameia is an nifia-i ed 01 heat detecting cameia

Conveniently, the camei a is adapted to be mounted on the fiont of the

vehicle

Piefeiably, the camera is adapted to be mounted on the lear of the

vehicle

Advantageously, sensor means aie piovided to sense when reverse geai

is selected and to send a signal to the control means, the contiol means

activating the cameia adapted to be mounted on the reai of the vehicle, the

signals representative of the image received by said camera being sent to the

image geneiatoi aπangement to generate an image

Conveniently, the contiol means is adapted to ieceive a signal ftom a

contiol switch

Piefei bly, the contiol switch is adapted to conti ol a global positioning

and navigation system Advantageously, the global positioning and navigation system is adapted

to send signals representative of an image to the image generator aπangement

to generate an image to be transmitted onto the combiner.

When the reverse camera is actuated or when the global positioning and

navigation system is activated, the image generator may transmit an image from

the camera on the front of the vehicle onto the larger region and anther image,

such as the image from the rear view camera or the image from the global

positioning and navigation system onto the smaller region of the combiner.

Preferably the image generator and combiner are adjustably

positionable. The image generator and combiner may form part of an integral

unit and the position of the whole unit may be adjusted. Alternatively the

combiner may be mounted, for example, on the windscreen of a vehicle, and

the image generator may be adjustably positionable relative to the combiner.

Conveniently, the control means is adapted to adjust the optical

transmission characteristic of the or each region to be substantially opaque

when high levels of ambient light are detected. Preferably, the control means is adapted to adjust the optical

tiansmission characteristic of the or each region to be substantially transparent

when low levels of ambient light are detected.

The invention relates to the head-up display when mounted in a motor

vehicle.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with refeience to the accompanying drawings in which:

FIGURE 1 is a side view of a motor vehicle incorporating a head-up display in accordance with the invention;

FIGURE 2 is a side view of the head-up display of Figure 1 ;

FIGURE 3 is a front view showing the combiner of the head-up display of Figure 2 and part of the windscreen of the vehicle;

FIGURE 4 is a block diagram of the head-up display of Figuies 1 to 3;

FIGURE 5 is a diagrammatic perspective view of the motor vehicle of Figure 1 showing the motor vehicle in a particular situation;

FIGURE 6 is a view of the combiner of the head-up display, as seen by the diiver of the vehicle of Figure 5, with the combiner in a first condition; FIGURE 7 is a view coπesponding to Figure 6 showing the combiner in a second condition;

FIGURE- 8 is a view coπesponding to Figure 7 showing the combiner in a third condition;

FIGURE 9 is a view coιτesponding to Figure 8 showing the combiner in a fourth condition; and

FIGURE 10 is a view coπesponding to Figure 9 showing the combiner in a fifth condition.

Refeπϊng initially to Figure 1 , a motor vehicle 1 is shown incorporating a head-up display 2 located within the cabin of the vehicle, a forward facing camera 3 mounted on the front of the vehicle and a rearward facing camera 4 mounted on the rear of the vehicle. The cameras may be any type of camera that converts an image to an electronic signal which is representative of the image, such as a camera that incorporates a charge coupled device. The camera may be sensitive to light in the visible part of the spectrum but, for the forward facing camera 3 at least, it is envisaged that an infra-red or heat-detecting camera would be used. The camera may include one or more micro-bolometers responsive to sensed radiation levels. Such a camera can provide valuable images when it is dark or when it is foggy.

Referring now to Figure 2, the head-up display 2 comprises an image generator arrangement in the form of a projector 5. The projector 5 is adapted to receive a signal from one or both of the cameras 3 and 4, and to generate, for example by means of a liquid crystal unit, an optical image which is the image projected by the projector 5. The projector, in use, emits a horizontal beam of light which passes through a focusing lens 6 mounted on a horizontal support element 7. The beam of light is directed to an inclined minor 8 mounted on the support element 7, and is reflected upwardly to be focused onto a combiner 9 that is mounted on part of the described unit, in this case the housing for the focusing lens 6. In an alternative embodiment the combiner 9 may be mounted on, or formed integrally with part of the windscreen 10 of the motor vehicle 1. In either event the combiner 9 is adjacent the inside of the windscreen 10 and is located in the ordinary line of sight of the driver 1 1 of the vehicle 1. The airowed lines 12 show the path of the light beam from the projector 5 to the combiner 9. In other embodiments the lens 6 may be omitted.

Signals representing an image from either the forward facing camera 3 or the rearward facing camera 4, may be sent to the projector 5 which projects the image onto the mirror 8. It is envisaged that the head-up display 2 may be adjustable, for example by adjusting the angle of tilt of the mirror 8, or by tilting the whole unit around a pivot point such that the image may be transmitted from the minor 8 to different sections of the combiner 9 to account for different drivers of the motor vehicle I being of different sizes. Of course, the line of sight of a tall driver is typically at a higher level than the line of sight of a short driver.

The combiner 9 is formed so that the optical transmission characteristics of the combiner may be adjusted. The combiner peπnits light from the exterior of the vehicle to enter the vehicle and be directed towards the eyes of the driver. The combiner also foπns a "screen" on to which the image from the projector is projected. Thus, the combiner should be at least partially transparent, in order to permit light from outside the vehicle to enter the vehicle, but also should be at least partially opaque to foπn a "screen" capable of displaying the projected image. The optical tiansmission characteristic of the combiner is a measure of the transparency or opaqueness of the combiner. Because, in the present invention, the optical transmission characteristic is variable, the degree of transparency or opaqueness may be adjusted so that the head-up display may operate in an optimum manner with different types of external conditions and intended use of the display.

In the presently described embodiment, the combiner 9 is of a laminated form, and is provided with at least one layer of liquid crystal material located between two transparent layers, the transparent layers being provided with transparent electrodes on the surfaces thereof adjacent the liquid ciystal material. The liquid crystal material contains elements which will change orientation in response to a change in an electric signal applied across the electrodes. The orientation of the liquid crystals of the combiner 9 controls how much light is permitted to pass through the combiner 9. Thus, by adjusting the electric signal applied across the electrodes, the optical transmission characteristic of the combiner may be adjusted. Liquid crystal arrangements of this type have been proposed for use in various contexts, such as display devices and welder's masks. Reference may be made to WO 95/29428 which discloses one type of liquid ciystal device.

In use of the described combiner 9, the optical transmission characteristic of the combiner 9 may be adjusted from a relatively high opacity, where very little light passes through the combiner 9, to a very low opacity, where a relatively high amount of light passes through the combiner 9. It is envisaged that the optical transmission characteristic of the combiner may be adjusted through a range of opacities ranging from approximately 20° o to approximately 80° o opacity. Refeπϊng now to Figure 3, the combiner 9 is shown located in the windscreen 10. The combiner 9 is of rectangular foπn and has two discrete regions 13 and 14, the optical tiansmission characteristic of which may be adjusted independently of one another, as will be described later in the description. The first region 13 is generally rectangular, save for a small rectangular cut-out at the top right-hand comer which accommodates the second region 14. However, it is to be appreciated that the second region 14 may occupy any position adjacent the first region 13 of the combiner 9 or may even be at a separate location within the combiner 9.

In ordinary use of the described aπangement, an image from the front camera 3 will be projected onto both the regions 13 and 14 of the combiner. However, different images may be projected, as will be described.

Refeπϊng now to Figure 4, the combiner 9 is connected to control means 15, for example a logic board or microprocessor.

The control means 15 is adapted to adjust the optical transmission characteristic of both the first region 13 and the second region 14 of the combiner 9. As will be further described, this adjustment may be to one of regions 13 or 14 independently, or to both regions 13 and 14 simultaneously.

The control means 15 is adapted to provide said adjustment of regions 13 and 14 in dependence upon one or more of a number of signals which are supplied to the control means 15.

A first signal may be sent to the contiol means 15 from a light detector 16, which optionally incorporates a fog detector, which is mounted to detect the ambient light level on the exterior of the vehicle 1 , or to detect the presence of mist or fog. It is to be appreciated that a variety of different types of light detector 16 may be used, including for example, a photoelectric cell. It is to be noted that the adjustment of the optical tiansmission characteristic of the regions 13 and 14 of the combiner 9 by the control means 15 will vary in dependence upon the signal received from the light detector 16. Thus, in very bright ambient conditions, the optical transmission characteristic may be adjusted so that the combiner 9 is quite opaque. This will reduce the intensity of light from the exterior of the vehicle 1 , while improving the intensity of the image projected onto the combiner 9 enabling the driver 1 1 to see both the scene on the exterior of the vehicle I and the projected image. In low light level ambient conditions for example, at night, the optical transmission characteristic may be adjusted so that the combiner 9 is substantially transparent, to enable the driver 1 1 to see the scene outside the vehicle 1 clearly. Only a small degree of opacity is required in such conditions for the projected image to be clearly visible.

The detector 16 may include components to detect fog such as a laser and means to measure the intensity of reflected laser light. If fog is detected, especially during daylight conditions, the combiner maybe adjusted so that it is very opaque to enhance the projected image.

A second signal or set of signals may be sent to the contiol means 15 from a control switch 17. The control switch 17 is a multi-function control switch, A first function of the contiol switch 17 is to enable the driver 1 1 to effect a manual adjustment of the optical transmission characteristic of the combiner 9. This may be desirable if, for example, the driver 1 1 should encounter foggy conditions, and there is no fog detector. Also the control switch 17 is adapted to actuate a global positioning and navigation system 18, as is well known in the art. When the global positioning and navigation system 18 is activated, the system will send, to the projector 5, signals representative of a supplementary image to be projected, which supplements the main image from the forward facing camera 3. The projector 5 is controlled, by the control means 15, to project the supplementary image onto the relatively small second region 14 of the combiner 9. Of course, the image from the front camera 3 may still be projected onto the first region 13.

A third signal may be sent to the contiol means 15 from a rear gear detector 19 indicating that the rear gear has been selected by the driver 1 1 of the motor vehicle 1. It is envisaged that the rear gear detector 19 may be for example, a contact switch, the switch being closed, and therefore generating the signal, when the gear stick of the motor vehicle 1 is moved into the rear gear gate by the driver 1 1 of the motor vehicle 1.

When the rear gear has been selected, the rearward facing camera 4 of the motor vehicle 1 will be activated and a signal representative of the image received by the rearward facing camera 4 is sent to the projector 5 of the head- up display 2. This image may be projected onto the combination of the regions 13 and 14, thus superseding the image from the front camera 3, but in this embodiment the image from the rearward facing camera 4 is projected, in the foπn of a supplementary image, onto the small region 14, while the main image from the front camera 3 is projected onto the region 13.

Whenever an image is projected onto the small region 14 which is not part of an image projected onto the region 13 (for example, when the global positioning and navigation system 18 or the rearward facing camera 4 is activated), the optical transmission characteristic of the region 14 may be adjusted to make it substantially opaque so that the projected image is visible regardless of the ambient light conditions on the exterior of the vehicle. It is to be noted that the control means 15 may adjust the optical transmission characteristic of either one of or both the regions 13 and 14 of the combiner 9 in dependence upon receiving one or more of the signals generated by the light detector 16, the contiol switch 17 or the rear gear detector 19.

Refeπϊng now to Figure 5, the motor vehicle 1 is shown in a position on a road 20. The forward facing camera 3 is shown at the front of the motor vehicle 1 and the rearward facing camera 4 is shown at the rear of the vehicle 1. The lines 21 represent the field of view of the forward facing camera 3. The lines 22 represent the field of view of the rearward facing camera 4. Thus, when the motor vehicle 1 is in the particular position shown, the forwardly facing camera 3 will detect two people 23 and a tree 24, whilst the rearward facing camera 4 will detect a dog 25.

Refeπϊng now to Figure 6, the combiner 9 is shown in a substantially transparent condition. It is envisaged that the optical transmission characteristic of the combiner 9 will be adjusted by the control means 15 to this substantially transparent condition when relatively little light is detected by the light detector 16, for example at night. The forward facing camera 3 will detect the two humans 23 and the tree 24 and these images will be focused onto the combiner 9 so as to be visible to the driver 1 1 of the vehicle 1. Because the combiner 9 is substantially transparent, the driver 1 1 will also be able to see the scene outside the vehicle 1. However, if the forward facing camera 3 detects an image which cannot actually be seen by the driver 1 1 , such as a person beyond the range of the headlights but emitting sufficient heat to be detected by the forward facing camera 3, the driver 1 1 will see the piojected image of that pei on, before the person actually becomes visible within the scene outside the vehicle 1. Refeπϊng now to Figure 7, the combiner 9 is shown in a substantially opaque condition. It is envisaged that the optical tiansmission characteristic of both regions 13 and 14 of the combiner 9 will be adjusted by the control means 15 to the substantially opaque condition when a signal received from the light detector 16 indicates that the light is relatively bright. Thus, in these conditions, the high ambient external light levels or "glare" from the relatively bright light will be reduced and the driver 1 1 of the vehicle 1 will be able to view the road ahead relatively easily, as well as seeing the image projected onto the combiner 9 of the projector 5. It is further envisaged that the optical tiansmission characteristic of the combiner 9 may be adjusted automatically or by use of the control switch 17 to the substantially opaque condition during foggy conditions, especially in daylight, when noπnal visibility in front of the vehicle will be relatively low. This will enliance the projected image. The fact that the driver cannot directly see the road outside the vehicle 1 because of the opaque combiner will not be of major concern, since the scene on the exterior of the vehicle is simply fog, the driver cannot, in any event, see the road.

Referring now to Figure 8, the combiner 9 is shown with the first region 13 in a substantially tiansparent condition, and the second region 14 in a substantially opaque condition. It is to be appreciated that the optical tiansmission characteristic of these regions will be adjusted in this way when the conti ol means 15 receives a signal from the light detector 16 indicating a low level of ambient light on the exterior of the vehicle and also receives a signal from the control switch 17 when the global positioning and navigation system is activated. The control means 15 controls the projector 5 so that the image from the forward facing camera 3 is focused on the first substantially transparent region 13 of the combiner 9 and the image generated by the global positioning and navigation system 18 will be focused onto the substantially opaque second region 14 of the combiner 9.

It is to be appreciated that, in this case, the image from the global positioning and navigation system 18 will therefore be clearly distinguishable, by the driver 1 1 , from the image detected by the forward facing camera 3.

Refeπϊng now to Figure 9, the combiner 9 is shown when reverse gear has been selected during darkness with the first region 13 in a substantially transparent condition, and the second region 14 in a substantially opaque condition. The image focused onto the first region 13 of the combiner 9 is that of the image received by the forward facing camera 3, and the image focused onto the second region 14 of the combiner 9 is that of the image received by the rearward facing camera 4.

Thus, the driver 1 1 of the vehicle 1 , when reverse gear has been selected, will have a clear view of the road behind the vehicle 1 focused by the second region 14 of the combiner 9 into his forward line of sight.

Refeπϊng now to Figure 10, the combiner 9 is shown when reverse gear has been selected in daylight. The optical tiansmission characteristics of the first region 13 and the second region 14 have both been adjusted by the control means 15 to be substantially opaque. Thus the image focused onto the first region 13 of the combiner 9 is that received by the forward facing camera 3 and the image focused on the second region 14 of the combiner 9 is that received by the rear facing camera 4.

In the described embodiment, a projector 5 is used as an image generator. In an alternative embodiment, a simple display screen, such as a cathode ray display, may be used with the display screen being located so that a reflection thereof is visible to the driver in the combiner.

In embodiments of this invention the optical transmission characteristics of one or both regions 13 and 14 of the combiner 9 may be adjusted so that the proportion of the external light that can pass through the combiner 9 is reduced as the intensity of the light increases, so that the intensity of the light entering the vehicle 1 through the combiner 9 is substantially balanced with the intensity of the image projected onto the combiner 9, so that the driver 1 1 can readily see the scene on the exterior of the vehicle 1 and also the projected image. The projected image from the front camera, or the rear camera, or the navigation system may cover the combination of both regions 13 and 14, or maybe present on only one region 13 or 14.

In the present Specification "comprise" means "includes or consists of and "comprising" means "including or consisting of .

Claims

CLAIMS:

1. A head-up display for a motor vehicle, the head-up display comprising a combiner adapted to be mounted in the field of view of a driver of the vehicle, an image generator arrangement to generate an image and to transmit the image onto the combiner, the combiner comprising at least one region wherein the optical transmission characteristic of the combiner may be adjusted, control means being provided to adjust the optical tiansmission characteristic of the region.

2. The head-up display of Claim 1 , wherein the image generator an angement is a projector.

3. The head-up display of Claim 1 or Claim 2, wherein the combiner comprises two said regions.

4. The head-up display of Claim 3 where one of said regions is substantially smaller than the other said region.

5. The head-up display of Claim 3 or Claim 4, wherein the optical transmission characteristic of the two regions are independently adjustable.

6. The head-up display of any one of the preceding claims, wherein a light detector is provided adapted to detect ambient light conditions on the exterior of the vehicle and to provide a signal to the control means, the control means controlling the optical transmission characteristic of at least one said region in response to said signals.

7. The head-up display of any one of the preceding claims further comprising a camera, the camera being adapted to send signals representative of an image to the image generator anangement.

8. The head-up display of Claim 7 wherein the camera is an infra-red or heat detecting camera.

9. The head-up display of Claim 7 or Claim 8, wherein the camera is

adapted to be mounted on the front of the vehicle.

10. The head-up display of Claim 7 or Claim 8, wherein the camera is

adapted to be mounted on the rear of the vehicle.

1 1. The head-up display of Claim 10, wherein sensor means are provided to

sense when reverse gear is selected and to send a signal to the control means,

the control means activating the camera adapted to be mounted on the rear of

the vehicle, the signals representative of the image received by said camera

being sent to the image generator arrangement to generate an image.

12. The head-up display of any of the preceding claims, wherein the control

means is adapted to receive a signal from a control switch.

13. The head-up display of Claim 12 wherein the control switch is adapted

to control a global positioning and navigation system.

14. The head-up display of Claim 13, wherein the global positioning and

navigation system is adapted to send signals representative of an image to the

image generator anangement to generate an image to be transmitted onto the

combiner.

15. The head-up display of Claim 1 1 or Claim 14 as dependant on Claim 4

and Claim 9 wherein, in use, the image generator transmits an image from the

camera on the front of the vehicle onto the larger region, and another image

onto the smaller region of the combiner.

16. The head-up display of any one of the preceding Claims wherein the

image generator and the combiner are adjustably positionable.

17. A head-up display according to any one of the preceding Claims when

mounted in a motor vehicle.