GB2060932A

GB2060932A - Checking vehicle headlamp alignment

Info

Publication number: GB2060932A
Application number: GB8033622A
Authority: GB
Original assignee: Cibie Projecteurs SA
Current assignee: Cibie Projecteurs SA
Priority date: 1979-10-17
Filing date: 1980-10-17
Publication date: 1981-05-07
Also published as: ES495915A0; JPS5664634A; FR2468114A1; FR2468114B1; DE3039325A1; ES8105477A1; GB2060932B; BE885721A; DE3039325C2

Abstract

A screen (4) is provided in front of a vehicle (2), and a semi-transparent mirror (3) is provided halfway between the vehicle and the screen. The mirror (3) is inclined at an angle alpha away from the vehicle, and forms a virtual image (10b) of the vehicle headlamp (9b). The line joining the headlamp and its image is inclined at the angle alpha to the horizontal, and defines the required direction of part of the headlamp beam, such as its upper cut-off. The part of the beam which passes through the mirror (3) forms an illumination pattern on the screen (4), and the relative position of this pattern and the virtual image (10b) indicates whether the headlamp alignment is correct. The apparatus is preferably provided at a filling station. <IMAGE>

Description

SPECIFICATION Checking vehicle headlamp alignment This invention relates to methods and apparatus for checking the alignment of vehicle headlamps.

Existing methods of checking the alignment of vehicle headlamps are generally satisfactory from the technical point of view, but they have certain other drawbacks. Flrstly, a conscious action is needed on the part of the vehicle driver in deciding to have his headlamps checked, and therefore the check may not be carried out as often as it should.

The checking procedure immobilises the vehicle for a more or less prolonged period; also, it is preferable for the existing checking methods to be carried out by a skilled person, rather than the vehicle driver, and since the skilled person will often not be immediately available, a waiting period is added to the period actually required to carry out the check.

According to one aspect of the present invention, in a method of checking the alignment of a vehicle headlamp the beam of the headlamp Is directed towards a screen and towards a semi-transparent mirror positioned approximately halfway between the headlamp and the screen, the screen and the mirror both being arranged approximately perpendicularly to the headlamp beam, with the mirror perpendicular to the required direction of a predetermined part of the headlamp beam, whereby any displacement of the part of the illumination of the screen produced by the said predetermined part of the headlamp beam from the virtual Image of the headlamp produced by the mirror indicates an error in the alignment of the headlamp.

According to a second aspect of the Invention, apparatus for checking the alignment of a vehicle headlamp comprises a surface on which the vehicle is to stand, a generally vertical screen mounted in the path of the headlamp beam from a vehicle standing on the surface. and, approximately halfway between the screen and the headlamps of a vehicle standing on the surface. a semi-transparent mirror In the path of the headlamp beam from the vehicle to the screen.

By providing such apparatus. It becomes possible for the driver of a vehicle himseif to check the alignment of nis headlamps, without requiring any very special care In the position ng of the vehicle relative to the apparatus The apparatus may be provided at a point where the driver would in any case stoo, such as a filling station. This should encourage the driver to check his headlamp alignment. since no extra manoeuvrlog and little or no extra tiloc will be required to carry out the check, especially If the check Is carried out while the vehicle Is being fueiled. In the case of vehicles whose headlamps can be adlusted from the dashboard, the driver need not even leave his seat.

The spacing between the semi-transparent mirror and the position ott tht vehicle is perferably sufficient for the vehicle to be @ble to drive past the mirror.

without reversing once the headlamp alignment check has been carried out The svstem shouldenable the importance of correct headlamp alignment to be brought home to drivers and get them into the habit of checking alignment and, where necessary, adjusting it, obviously with increased safety for all. This educational purpose can also be achieved with a reduced number of installations, provided they are suitably selected. Service stations at the entrance to major motorways are obviously a first choice, since drivers automatically stop here to fill up with fuel, often before undertaking a long-distance journey under abnormal loading conditions which require correct tion of the headlamp alignment.

The invention may be carried Into practice in various ways, but one specific embodiment will now be described by way of example, with reference to the accompanying drawings, of which: Figure 1 is a top plan view of a headlamp alignment checking system embodying the invention, installed at a filling station; Figure2 is a section of this installation on the vertical plane ll-ll in Figure 1; Figures 3 to 5 show the images which are seen by a person using the checking system, for correct adjustment in the case of a dipped beam of the European type and of the American type respectively, and in the case of a main beam (all for vehicles which are to be driven on the right of the road; the images should of course be reversed for vehicles which are to be driven on the left).

Referring more specifically to Figures 1 and 2, the filling station has a flat surface 1, and petrol pumps 8, and a vehicle standing at the pumps is shown at 2.

The headlamp alignment checking system is provided ahead of the vehicle 2, and consists essentially of a semi-transparent mirror 3 and a screen 4.

The term "semi-transparent mirror" generally denotes any mirror which. when It receives a beam of light, reflects part of the light and allows the rest to pass therethrough; examples are unsilvered mirrors, sheets of transparent plastics or glass, and so on.

The mirror 3 and the screen 4 are flat. and are mounted approximately vertical, and approximately parallel to one another, the surface 1 being approximately horizontal, at least In the area of the predetermined position where the vehicle 2 stands while the alignment of its headlamps shown at 9a and 9'ai Is checked.

This predetermined position, which consequently controls the positioning of the mirror 3 and the screen 4, Is advantageously Indicated on the surface 1 by any suitable means, e.g. by marking on the surface 1 or. preferably, by means of oarallel guide rails shown diagrammatically at 5, between which the driver engages the wheels of the vehicle 2 and which. as the vehicle moves forwards. align the central longitudinal axis of the vehicle along 3 predetermined direction 6 parallel to the rails 5; of course, the rails 5 are only one example of the possible methods of achieving this result, In addition to alioni no the longitudinal axis of the vehicli 2 In the iii rOOtihil 6. the position of the vehicle along this iii reirtlo ii spoil, d also be correct; the surface 1 may 1)1' T Irke(l 'or this purpose or else means may be used to form a stop or abutment which can be felt when the vehicle moves forwards in the direction 6 into contact with the stop, but which the vehicle can easily clear on moving forwards again; for example a flexible cane or the like 7 could be secured on the surface 1 in a vertical position. As the driver moves forwards in the direction 6 the vehicle radiator comes into contact with the cane 7; when contact is made, the predetermined position has been reached but the vehicle can nevertheless readily move forwards once the headlamp alignment check (and possible adjustment) has been made, with the cane 7 bending beneath the vehicle.

In Figures 1 and 2 the vehicle 2 is shown in the predetermined position in which the headlamp alignment check and adjustment Is carried out.

When, as in the present example, the checking system is provided at a filling station, the predetermined position is preferably so chosen that the rear of the vehicle 2 is situated in front of the petrol pumps 8.

As seen in plan view, the mirror 3 is situated a distance 11 in front of the headlamps 9a and Sb perpendicularly to the predetermined direction 6; the screen 4 is also disposed in a similar orientation a distance 12 from the mirror 3 on the side remote from the headlamps 9a and Sb.

The distance 1 between the screen 4 and the mirror 3, measured parallel to the direction 6 and to the surface 1, Is as close as possible to the distance 12 measured in the same way between the mirror 3 and the headlamps 9a and 9b of the vehicle, and the mirror 3 Is Inclined away from the headlamps 9a and 9b by an angle la corresponding to the required downward deflection of a predetermined part of each headlamp beam, usually that part of the beam directed along the optical axis of the headlamp 9a or Sb. Advantageously, the distances 11 and t7 are of the order of several metres, e.g. 5 metres, so that there Is some tolerance on the positioning of the vehicle in the predetermined position, e.g. some tens of centimetres with respect to the distance trn, so that the vehicle can, without complicated man oeuvring, be placed in a position in which the headlamp check and adlustment can be carried out satisfactorily; the vehicle may occupy any lateral position within limits compatible w th the dimen sions of the mirror and the screen. provided its longitudinal axis Is approximately parallel to the direction 6.

The mirror 3 will form virtual Images 10d and lOb of the headlamps 9a and So respectively, and these Images are vlslble from the area of the vehicle 2.

ancl. more particularly, from the or ver s seat of the vehicle. These virtual images are positioned substantially at the screen 4.

The screen 4 should theoretlcally he strictly para ilel with the mirror 3, as indicated dlagrammatlcally at 4a In Figure 2. the distances ti and t . then being measured perpendicularly to the mirror 3. However.

In view of the generally small vaiue of the angle of beam inclination 1 and the small oifferences In level with respect to the surface 1 between the various headlamps of a given vehicle or the headlamps of different vehicles. the headlamp checks and adjust- ments can be carried out with satisfactory accuracy by using a screen 4 which is not strictly parallel to the mirror 3, e.g. a screen 4 which Is approximately vertical; more particularly, the screen 4 may advantageously be a wall of a building.

The position of the images 10a and 1 Ob on the screen 4 is unaffected by the adjustment of the headlamps 9a and Sb; the directions of the centre line connecting the headlamp 9a to its Image 10a and of the centre line connecting the headlamp sub to its image 1 Ob will always lie normal to the mirror 3, and therefore indicate the correct orientations of the aforesaid predetermined parts of the headlamp beams.

That part of the beam emitted by the headlamp 9a or Sb which passes through the mirror 3 produces on the screen 4 an illuminated area whose position depends on the orientation of the beam.

If the adjustment of the headlamp alignment is correct, i.e. if the direction of the predetermined part of the beam emitted by the headlamp coincides with the centre line connecting the headlamp 9a or 9b and its image 10a or lOb, i.e. If the predetermined part of the beam meets the mirror 3 along a line perpendicular to the mirror 3, the said predetermined part of the beam will be incident on the screen 4 at a position coinciding with the image of the headlamp produced by reflection from the mirror 3.

Depending upon the type of headlamp which is being checked, the illuminated area and the virtual image at the screen 4 wlll appear to an observer as shown in Figure 3, Figure 4 or Figure 5 (which are drawn for a vehicle to be driven on the right-hand side of the road).

Figure 3 shows the case of a headlamp of the European type which Is characterised by the beam having an upper cut-off In the form of a discontinuous line which usually defines a wide-open "V".

Such headlamps are designed to Illuminate the road and the near side verge, without dazzling the drivers of oncoming vehicles using the same road. This type of illumination is obtained by using a suitable mask to blank out the bottom part of the reflector so that only the rays emitted upwards by the lamp of the headlamp are reflected, I.e., the rays which extend downwardly outside the headlamp.

In this case, the virtual Image lOa or lOb of the headlamp, formed by reflection from the mirror 3, Is shown at 1,, and has an outer contour Identical to that of the headlamp, as shown in broken lines In Figure 3.

The area illuminated by projection of the beam on to the screen 4 through the mirror 3 takes the form of a bright lower zone D and a darker top zone E.

separated by a line C which syndicates the shape of the upper cut-off of the beam, and therefore has the shape of a wide-open V having an apex F. The part of the beam directed towards the apex F constitutes the predetermined part of the beam, whose Inciination should be 1. If the alignment of the headlamp Is correct, the apex F coincides with the centre of the virtual Image, as shown In Figure 3. In general. the adlustment wlll be sufficlently accurate if the apex lies anywhere within the Image 1,.

If, on the other hand, the adlustment is Incorrecr.

i.e., if the direction of the predetermined part of the beam emitted by the headlamp diverges from the correct predetermined position, either laterally as indicated diagrammatically in Figure 1 in the case of the headlamp 9a or upwardly as indicated diagrammatically in Figure 2 in the case of the headlamp 9b.

or in any other manner, the apex F of the line separating the zones D and E of the projection P, of the beam on to the screen 4 is displaced from the fixed image It of the headlamp obtained by reflection from the mirror 3; by adjusting the headlamp alignment the relative positions can then be brought to the predetermined relative position shown in Figure 3.

Figure 4 illustrates the case of an American type headlamp in which 12 denotes the virtual Image of this headlamp produced by reflection from the mirror 3, as seen by an observer situated on the same side of this mirror as the vehicle 2, while P2 is the bright spot produced on the screen 4 by projection of the beam through the mirror 3.

In this case the correct setting of the headlamp is one in which the top left-hand corner of the bright spot P2 coincides with the bottom right-hand corner of the virtual image 12; if this Is not the case, the alignment of the headlamp should be adjusted until this predetermined relative position is obtained.

Figure 5 shows the case of a main beam, and 3 denotes the headlamp Image formed by reflection in the mirror 3, as it appears to an observer situated on the same side of the mirror as the vehicle 2, while P3 is the bright area produced by projection of the beam on to the screen 4 through the mirror 3; In this case the correct setting is a relative centring of the areas P3 and i3; if the two areas do not appear to be centred the headlamp alignment is adjusted until centring is obtained, I.e., until the centre line of the beam and the predetermined centre direction coincide.

Of course, these three examples relate to the regulations at present In force; other examples are perfectly possible if different requirements are to be met.

Similarly, the Invention can be modified In various ways in comparison with the example shown In Figures 1 and 2. For example, the system can be installed In places other than a filling station, and the arrangements described can be varied. for example by providing means enabling the Inclination of the mirror 3 to be adlusted according to the regulations to give different angles of deflection, as shown In Figures 1 and 2, an opaque longitudinal partition 11 may be provided which Is substantially vertical and extends along the central direction 6 between the screen 4 and the mirror 3 to provide separation sn this zone between the beams emitted by the respeclive headlamps 9a and Sb and to allow separate observation of their respective proiections on to the screen 4 through the mirror 3.

Claims

1 A method of checkinq the alignment of a 'ehicle headlamp, in which method the beam of the headlamp is directed towards a screen ai1d towards a semi-transparent mirror positioned approximately halfway between the headlamp and the screen, the screen and the mirror both being arranged approximately perpendicularly to the headlamp beam, with the mirror perpendicular to the required direction of a predetermined part of the illumination of the screen produced by the said predetermined part of the headlamp beam from the virtual image of the headlamp produced by the mirror indicates an error in the alignment of the headlamp.

2. A method as claimed in Claim 1, in which the said predetermined part of the headlamp beam is that part which is directed along the optical axis of the headlamp.

3. A method as claimed in Claim 1 or Claim 2, which also includes the step of adjusting the headlamp to eliminate any displacement of the said part of the illumination from the said virtual image.

4. A method as claimed in Claim 1 or Claim 2 or Claim 3, in which the headlamp is a European code headlamp, producing a dipped beam whose upper cut-off is a discontinuous line having an apex or discontinuity, and the said predetermined part of the headlamp beam is that part close to the apex of the cut-off.

5. A method as claimed in Claim 1 or Claim 2 or Claim 3, in which the headlamp produces a main beam, and the said predetermined part of the headlamp beam is the central part of the beam.

6. A method as claimed in Claim 1 or Claim 2 or Claim 3, in which the headlamp is of American type, producing a dipped beam, and the said predetermined part of the headlamp beam is the top off-side part of the beam, which, for correct alignment of the headlamp, coincides with the lower near-side part of the virtual Image of the headlamp.

7. A method of checking the alignment of a vehicle headlamp, the method being substantially as herein described, with reference to the accompanying drawings.

8. Apparatus for carrying out the method of any of the preceding claims.

9. Apparatus for checking the alignment of a vehicle headlamp, the apparatus comprising a surface on which the vehicle Is to stand, a generally vertical screen mounted in the path of the headlamp beam from a vehicle standing on the surface, and, approximately halfway between the screen and the headlamps of a vehicle standing on the surface, a semi-transparent mirror in the path of the headlamp beam from the vehicle to the screen.

10. Apparatus as claimed In Claim 9. In which the semi-transparent mirror leans towards the screen, relative to a piane perpendicular to the said surface.

by an angle equal to the required inclination of the headlamp beam.

11. Apparatus as claimed in Claim 9 or Claim 10, In which the said surface has guiding means arranged to define the position of the vehicle on the surface.

12. Apparatus as claimed in Claim 9 or Claim 10 or Claim 11. which also Includes, between the screen and the mirror, an opaque longitudinal vertical partition.

13. Apparatus as claimed in any of Claims 9 to 12, in which the distance between the mirror and the screen and between the mirror and the headlamps of a vehicle standing on the surface is of the order of several metres.

14. Apparatus for checking the alignment of a vehicle headlamp, the apparatus being substantially as herein described, with reference to the accompanying drawings,