GB2465470A

GB2465470A - Head up device which can vary the image according to the background

Info

Publication number: GB2465470A
Application number: GB0920079A
Authority: GB
Inventors: Winfried Koenig
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-11-18
Filing date: 2009-11-17
Publication date: 2010-05-26
Anticipated expiration: 2029-11-17
Also published as: DE102008043828A1; GB0920079D0; GB2465470B; FR2938660B1; FR2938660A1

Abstract

The photometric parameters (such as light density or colour distribution) of a character which can be projected in front of a screen of a vehicle, can be ascertained by receiving 100 via an interface an item of information relating to photometric parameters in an area surrounding the vehicle, determining 103 an angular range of the surrounding area, in front of which the character appears for an occupant, determining 105 photometric parameters in the angular range, based upon the information relating to photometric parameters in the area surrounding the vehicle, and determining 108, 113 at least one photometric parameter of the character which is adapted to the photometric parameters in the angular range. A control signal may be used to change the photometric parameters to aid visibility of the character.

Description

Method and control device for determining photometric parameters of a proiectable character The present invention relates to a method of determining photometric parameters of a character, which can be projected in front of a screen of a vehicle, a method of projecting a character in front of a screen of a vehicle and a control device and a computer program product therefor.

DE 198 13 300 C2 relates to a position of the display of a Head-up Display (HUD), The position of the display can be selected such that although it lies in the driver's field of vision, it disturbs the driver to the least possible extent.

A head-up display can display an unprocessed image or symbol, or a camera image which has been altered by means of image processing.

The image or symbol of the head-up display is referred to hereinafter as a "character". The character appears to the driver of a vehicle as a virtuaf image in front of a background, whose properties cannot be controlled.

The background can be very different in terms of its light density and colour, Extreme cases include eg. a wintery, snowcovered road in sunshine or a tunnel entrance. In terms of its fight density, the background can be predominantly homogeneous or else very highly structured. An homogeneous background is eg. a concrete roadway in diffuse daylight.

A very highly structured background can be an urban environment with vehides and house walls. In all of these cases, It is necessary to ensure that the character stands out dearly from the background for the driver.

DE 102005052424 Al relates to a projection display, in which an image is projected onto a windscreen of a vehicle. The contrast of the image representation can be regulated In dependence upon the colour and/or brightness In the vldnfty of the vehicle.

Inthecaseof known systemsfortheprojectlonofa characterinfrontofa screen, the position of the character and thus the photometric parameters of the background do not have any combined effect. Therefore, Image representation is frequently not optimum espedally under difficult viewing conditions.

Against this background, the present Invention presents a method of determining photometric parameters of a character which can be projected Infrontofascreenofavehicle, a method of projectingacharacter In front of a screen of a vehicle and finally a corresponding computer program product In accordance with the independent claims. Advantageous embodiments are apparent from the respective subordinate claims and the

description hereinafter.

The invention is based upon the knowledge that the dearness of the dIsplay of a head-up display can be ensured even under difficuft viewing conditions, If a displayed character Is optimally adapted to the background located directly behind the character. On the one hand, it Is suitable for this purpose to adapt the light density of the character to suit the light density of the background. On the other hand, ft Is also suitable to determine the optimum colour of the head-up display character and represent the character In this optimum colour relative to the background, in order to ensure the dearness of the display.

The present Invention provides a method of determining photometric parameters of a character which can be projected as a virtual Image in front of a screen of a vehide, comprising the steps ot receiving via an Interface an ftem of information relating to photometric parameters In an area surrounding the vehide; determining an angular range of the surroundIng area, in front of which the character appears for an occupant; determining photometric parameters in an angular range based upon the information relating to photometric parameters in the area surrounding the vehide; and determining at least one photometric parameter of the character which is adapted to the photometric parameters in the angular range.

the driver of the vehide. The photometric parameters can indude a light density (cd/m2) and a colour which can be described approximately by means of a colour location, i.e. colour coordinates. The character can be an Image, a symbol, a script or In general one or a piuralfty of pixels. The character can be defined by a character light density, a colour, an angular range (expansion) and an (angular) position. The character can be projected by means of a projection device or a head-up display onto the screen in such a manner that to the occupant it appears as a virtual character on or in front of the screen. In this case, the phrase "in front of the screen" can mean outside the vehicle. The area surrounding the vehicle can be a surrounding area of the vehicle located in the region of the screen. The information relating to the photometric parameters of the surrounding area and the information to be derived from this relating to the distribution of light density and colour of the background can be determined by means of an image signal generated by a camera. The information relating to the photometric parameters of the surrounding area can comprise a plurality of measurement values which can be allocated to individual regions of the surrounding area. The (character) background can be a section of the surrounding area. The angular range can thus define a section of the entire surrounding area which is defined by the position of the character and the occupanVs angle of view onto the character. The position of the character can appear for the occupant in a fixed angular position and within a fixed angular range, if the character is not directly related to an object in the surrounding area. However, if the character is related to an object in the surrounding area, e.g. a warning symbol, then its angular position and its angular range can be variable for the occupant. The information relating to the photometric parameters of the surrounding area can include an item of information relating to a light density distribution and/or relating to a colour distribution in the angular range of the background. From these photometric parameters of the background, it is possible to determine an optimum light density and/or colour of the character.

The photometric parameters in the angular range can be determined by means of a weighting function from the information relating to the photometric parameters in the area surrounding the vehicle, wherein an item of information of a region of the surrounding area located closer to the character can be weighted to a greater extent than an item of information of a region of the surrounding area located further away from the character. In this way, it is possible to avoid any mismatching of the character by reason of inhomogeneous light conditions.

In accordance with one embodiment, the method can include a step of determining a source of glare in the surrounding area, based upon the information relating to the photometric parameters in the area surrounding the vehicle, wherein the at least one adapted photometric parameter of the character can be determined whilst taking the source of glare into account.

It is thus possible to take into account eg. scattering of the source of glare in the occupanVs eye which can generate a haze light density on the occupants retina and therefore make a higher light density of the character necessary.

Furthermore, the method can include a step of determining an adaptation light density of the occupant, wherein the at least one adapted photometric parameter of the character can be determined whilst taking the adaptation light intensity into account, This renders it possible eg. to increase the light density of the character if the driver has been very brightly adapted in an immediately preceding time segment.

Furthermore, the method can include a step of receiving via the interface an item of information relating to an occupant anomaly, wherein the at least one adapted photometric parameter of the character can be determined whilst taking the information relating to the occupant anomaly into account. In this manner, the representation of the character can be adapted individually to the occupant.

The photometric parameters can define a light density. In addition or as an alternative, the photometric parameters can define a colour distribution.

Therefore, in the case of a bright background the light density of the character can be increased and in the case of a darker background it can be reduced. The colour of the character can also be selected according to a background colour and can be adapted to a changing background colour.

The present invention also provides a method of projecting a character in front of a screen of a vehicle, comprising the steps of: receiving via an interface an item of character information to be represented by the character; determining at least one adapted photometric parameter of the character in accordance with the inventive method of determining photometric parameters of a character which can be projected in front of a screen of a vehicle; determining a control signal for displaying the character based upon the character information and the at least one adapted photometric parameter; and providing the control signal to a display device for displaying the character.

Therefore, the approach in accordance with the invention can be utilised advantageously in the case of known projection devices. It is thus possible eg. to adapt the display of a head-up display.

The object of the invention can also be achieved quickly and efficiently by virtue of the embodiment of the invention in the form of a control deviceS In this case, a control device can be understood to be an electrical device which processes sensor signals and outputs control signals in dependence thereon The control device can comprise an interface which can be formed in terms of hardware and/or software. In the case of a design in terms of hardware, the interfaces can be eg. part of a so-called system ASIC which includes a very wide range of functions of the control device. However, it is also possible for the interfaces to be dedicated integrated circuits or to consist at least partially of discrete devices. In the case of a design in terms of software, the interfaces can be software modules which are present eg. on a microcontroller alongside other software modules.

Also advantageous is a computer program product with program code which is stored on a machinereadable medium such as a semiconductor memory, a hard disk storage unit or an optical memory and is used for the purpose of carrying out the method in accordance with one of the above described embodiments, if the program is executed on a control device.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawing, in which: Figure 1 shows a flow diagram of the method in accordance with the invention, according to one exemplified embodiment of the present invention.

Like or similar elements can be designated in the following Figures by like or similar reference numerals. Furthermore, the Figures of the drawings, the description thereof and the claims include numerous features in combination. It is apparent to a person skilled in the art that these features can also be considered individually or they can be combined to form further combinations which are not explicitly described in this case.

Figure 1 illustrates a flow diagram of a method of determining photometric parameters of a character, which can be projected in front of a screen of a vehicle, in accordance with an exemplified embodiment of the present invention. In accordance with the invention, calculations are performed in 2() several steps, the values can include the photometric parameters of the character displayed by means of a headup display, in order to be observed easily. These parameters can be adjusted on the head-up display.

In a first step 100, photometrIc parameters relating to an area wounding the vehicle are received. This Information can be received via an Interface, e.g. a camera. A light density distribution and a colour location distribution can be determined from the camera image.

In a second step, an angular range of the surrounding area Is determined, in front of which the character appears for the occupant For this purpose, ft can Initially be determined In a step 102 whether the occupant's angie of view is variable with respect to the character. If the angle of view is fixed, then in a step 103 a section of the background Image can be determined according to the angle of field. If the angle of view is variable, then In a step 104 the angle of field can be determined according to an object in the driving scene. Subsequently, in step 103 the section of the background image can be determined according to this angle of field. The determination of the angular range can be based e.g. upon data provided by a control device of the head-up display.

Therefore, in accordance with the Invention the scene in front of the driver can initially be recorded by a camera having a corresponding dynamic range. In the background image which is recorded by the camera, the angular ranges can be calculated, In front of which the head-up display character will appear for the driver. Here, a dIstinction is to be made between a number of cases.

In the first case, the character appears at a fixed angular range for the driver. This is typical if the information carried by the character is not directly related to objects in the driving scene outside the vehicle. This is the case e.g. with a speed display or a navigation symbol. In this case, the section of the background image which corresponds to this fixed angular range is to be determined.

In the second case, the character of the head-up display is directly related to an object outside the vehicle. The head-up display can display e.g. a warning symbol or a marking which surrounds a relevant object on the roadway. For example, a frame can be displayed around a pedestrian. In this case, the angular range of the head-up display character changes for the driver continuously. Therefore, the partial image corresponding to the current angular range is to be determined from the background image.

In a third step, a light distribution is determined in the angular range from the information relating to the photometric parameters of the area surrounding the vehicle. For this purpose, in a step 105 the light density and colour location distribution are determined in the area surrounding the

character angle of field,

In order to calculate the surrounding area light density and the character light density, the surrounding area light density around the angular range of the headup display can first be determined from the camera image. In the event of an inhomogeneous background, the regions directly around the headup display are to be weighted to a greater extent than regions ii located further away. This can be accomplished by means of a two-dimensional weighting function, by means of which the individual light density values of the background image are weighted. The maximum of the function is disposed in the centre of the head-up display character. By summing and averaging the weighted individual light densities, an effective surrounding area light density can be calculated.

From known models of minimum character light density (based upon extensive tests with test subjects, published by Blackwell, Bhise et al,) the minimum character light density and a character light density, in which reliable and convenient clearness of display is ensured, are then calculated.

In a further step 106, it is possible to determine whether a source of glare is present. If a source of glare is present, then in a step 107 an increased light density requirement caused by the source of glare can be calculated.

In at least one further step, at least one photometric parameter of the character adapted to the light distribution is determined. For example, in a step 108 a character light density can be calculated. In so doing, the increased light density requirement calculated in step 107 can be taken into account.

It is thus possible in accordance with the invention to take sources of glare into account. In the event that the background image has a light source present therein whose light density very greatly exceeds the light density of the other light sources or surfaces, this source of glare can be taken into account separately. It increases the light density requirement of the character, in that ft generates a haze light density e.g. by means of scattering on the retina of the driver's eye. In this case, calculation models are also known (e.g. from Adrian) which require as input variables the angular position, the expansion and light density of the source of glare.

These variables can likewise be determined from the image of the camera.

In a step 109, the adaptation state of the drive can be evaluated. The adaptation state of the driver can be taken into account In the calculation of the character light density in step 108. Therefore, the adaptation state of the driver's eye can be taken Into account on the basis of previous light Impressions.

Therefore, in accordance with the invention It Is possible to take into account the adaptation state of the driver. To this end, from the knowledge of the light density distribution In the camera image and the driver's viewing direction in the immediately preceding time segment ft is possible to suggest the instantaneous adaptation state of the drive. In turn, this can be incorporated into the model of the character light density.

As a consequence, a correction factor can be calculated for the character light density. Therefore, e.g. In the case of a very brightiy adapted drive a hIgher character light density is required in order to achieve the same quality of dearness of the character. In particular, sources of glare are to be taken into account in this case. If the driver's viewing direction is measured continuously, the time progression thereof In the preceding moments can be taken into account Earlier viewing directions and viewed light densities after a fading function are to be weighted less than current light densities in the viewing direction. Functions of this kind are also known in prlndpie. If the viewing direction is not detected, then it is possible to determine a weighting function from the knowiedge of typical viewing direction distributions. By means of the weighting function the background light densities in the driver's field of vision are weighted and combined to form a typical adaptation light density. For example, typical viewing direction distributions can be used for journeys on typical classes of road. It Is also known that in the case of photo-optical illumination levels the adaptation state of the driver Is determined substantially by a narrow angular range In the viewing direction. Therefore, this angular range cai be weighted to a very significant extent After calculation of the required character light density, ft is possible In a step 110 to verify whether this character light density can be achieved by the head-up display. In this case, the character can be represented in a step 111 with the calculated required light density.

If the necessary character light density cannot be achieved by the head-up display, then It Is possible in a step 112 to verify whether the head-up display can represent the character in different colours, If the character colour is variable, then ft is possible in a step 113 to select a colour for the

character which contrasts with the background.

In a step 1 14, the character can be represented with the contrast colour.

Depending upon whether an adaptation of the colour of the character is required or even possible, step 114 can be carried out after step 111 or step 113.

Therefore, the approach in accordance with the invention renders it possible to verify the colour coding. If the maximum light density of the character is not sufficient to provide a sufficient light density contrast with respect to the background, it is possible to establish whether adequate recognition of the character can be achieved by an additional colour contrast of the character. This is preferably accomplished in characters, whose colour does not have any established significance, i.e. in which there is no generally known colour coding. If e.g. the colour of a character is red and this is intended to signify "danger or yellow is used as a "warning", the colour of this type of character is left as is where possible.

However, if the character is only intended to provide an indication, e.g. a green arrow for displaying a route guidance system, the colour can be changed. For example, a change in colour from green to purple can be made, in order to achieve an additional colour contrast with the countryside as the background. This can be accomplished by deciding initially whether sufficient light density contrast can be achieved If not, it is initially possible in the video image to determine the colour of the background, in front of which the character is to appear. A colour which is at an adequate distance in the colour space can then be calculated and adjusted in the head-up display, in order for a driver with normal colour vision to be able to distinguish it, In accordance with the invention it is also possible to take into account specific characteristics of individual drivers. For this purpose, specific characteristics of the user can also be taken into account in each of the described steps. They can relate to e.g. the visual acuity under photo-optical and measurement-optical illumination conditions or anomalies in colour vision. Such specific characteristics can be evaluated in part from the driver's age, but preferably they are incorporated in a known manner through the personalisation of the vehicle, e.g. a person-related key or the like which carries additional information of this type relating to the user and transmits it to the vehicle.

For this purpose, in a step 115 it is possible to identify the driver. In a step 116, it is possible to verify whether a driver anomaly is present. If there is is no driver anomaly, the method can be carried out as described. However, if a driver anomaly is present, the driver anomaly can be read out in a step 117. If the anomaly relates to the light density requirement, then in step 107 it is possible, in addition to calculating the increased light density requirement caused by the source of glare, to calculate the increased light density requirement caused by the anomaly. If the anomaly relates to the driver's adaptability, then this can be taken into account in step 109, in which the adaptation state of the driver is evaluated. If the anomaly relates to colour perception, then this anomaly can be taken into account in step 1 13 during the selection of the contrast colour.

After steps 111 and 114, in which the character is represented, the cycle illustrated in Figure 1 can be repeated with the next camera image.

The method steps described can be performed by a corresponding device which comprises corresponding interfaces and logic units. In particular, the method steps can be performed by a control device of a head-up display.

The exemplified embodiments described are selected by way of example only and can be combined with each other. In particular, individual or several method steps can be left out or can be performed in a different sequence or repeatedly.

Claims

Claims 1. A method of determining photometric parameters of a character which can be projected as a virtual image in front of a screen of a vehicle, comprising the steps of: receiving (100) via an interface an item of information relating to photometric parameters in an area surrounding the vehicle; determining (103) an angular range of the surrounding area, in front of which the character appears for an occupant; determining (105) photometric parameters in the angular range, based upon the information relating to photometric parameters in the area surrounding the vehicle; and determining (108, 113) at least one photometric parameter of the character which is adapted to the photometric parameters in the angular range.
2. A method as claimed in claim 1, wherein the photometric parameters in the angular range are determined (105) by means of a weighting function from the information relating to the photometric parameters in the area surrounding the vehicle, wherein an item of information of a region of the surrounding area located closer to the character is weighted to a greater extent than an item of information of a region of the surrounding area located further away from the character.
3. A method as claimed in any one of the preceding claims, including a step (106) of determining a source of glare in the surrounding area, based upon the information relating to the photometric parameters in the area surrounding the vehicle, wherein the at least one adapted photometric parameter of the character is determined (108, 113) whilst taking the source of glare into account.
4. A method as claimed in any one of the preceding claims, including a step (109) of determining an adaptation light density of the occupant, wherein the at least one adapted photometric parameter of the character is determined (108, 113) whilst taking the adaptation light density into account.
5. A method as claimed in any one of the preceding claims, including a step (117) of receiving via the interface an item of information relating to an occupant anomaly, wherein the at least one adapted photometric parameter of the character is determined (108, 113) whilst taking the information relating to the occupant anomaly into account.
6. A method as claimed in any one of the preceding claims, in which the photometric parameters define a light density.
7, A method as claimed in any one of the preceding claims, in which the photometric parameters define a colour distribution.
8. A method of projecting a character as a virtual image in front of a screen of a vehicle, comprising the steps of: receiving via an interface an item of character information to be represented by the character; determining at least one adapted photometric parameter of the character as claimed in any one of claims 1 to 7; determining a control signal for displaying the character based upon the character information and the at least one adapted photometric parameter; and providing (111, 114) the control signal to a display device for displaying the character.
9. A control device for controlling a projection device for the projection of a characters in order to perform all of the steps of a method as claimed in any one of claims 1 to 8.
10. A computer program product with program code which is stored on a machine-readable medium, for performing the method as claimed in any one of claims 1 to 8 when the program is executed on a control device as claimed in claim 9.
11. A method of determining photometric parameters of a vehicle substantially as herein described with reference to, and as illustrated in, the accompanying drawings.
12. A method of projecting a character as a virtual image substantially as herein described with reference to, and as illustrated in, the accompanying drawings.
13. A control device for controlling a projection device for the projection of a character substantially as herein described with reference to, and as illustrated in, the accompanying drawings.
14. A computer program product substantially as herein described with reference to, and as illustrated in, the accompanying drawings.