GB2248679A

GB2248679A - Method of measuring and adjusting the optical axis of a headlight

Info

Publication number: GB2248679A
Application number: GB9121350A
Authority: GB
Inventors: Nagatoshi Murata; Shinichi Watanabe; Manabu Tuchida
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1990-10-09
Filing date: 1991-10-09
Publication date: 1992-04-15
Anticipated expiration: 2011-10-09
Also published as: JP2566847B2; GB2248679B; JPH04147030A; GB9121350D0

Abstract

An optical axis of a headlight is measured by disposing a lattice member 3 in front of the headlight. The lattice member has a plurality of longitudinally elongated lattice holes 2 which are arranged in a form of a matrix. An illuminated area and an illuminance of light beams to be transmitted through the lattice member are measured at each of illuminating regions which are divided into a form of a matrix by the lattice holes. The position of a light source of the headlight is located from an illuminating region of maximum illuminated area and a position of an optical axis of the headlight is located from an illuminating region of maximum illuminance. The optical axis is adjusted depending on the located position of the light source and the position of the optical axis such that the inclination angle of the optical axis coincides with a set inclination angle. <IMAGE>

Description

METHOD OF MEASURING AND ADJUSTING OPTICAL AXIS OF HEADLIGHT BACKGROUND OF THE INVENTION This invention relates to a method of measuring an optical axis of a headlight of an automobile or other vehicles and to a method of adjusting the optical axis by utilizing this method of measuring.

In order to secure a front visibility as well as to prevent blinding of a driver on an automobile running in the opposite direction, there are regulations on vertical and horizontal illuminating directions of a headlight.

According to the Japanese domestic regulations, there are specified the position of an optical axis and the illuminance of a high beam on a screen 10 meters ahead.

However, in order to reduce the space required for measuring them, it is also approved to measure the position of the optical axis and the illuminance on a screen 3 meters ahead for thereafter converting them to values corresponding to those on the screen 10 meters ahead.

Conventionally, there is disclosed a method in Japanese Published Examined Patent Application No.

63849/1988, in which an illuminating pattern of headlight beams illuminated on a screen is pictured, isolux region having illuminance above a predetermined level is located by picture processing, and a geometric center of gravity of the located isolux region is calculated, thereby measuring the position of the optical axis on the screen.

The headlight is so designed that, at a short distance, there is formed an illuminating pattern which is laterally spread and is not symmetrical relative to the optical axis to improve the visibility of a road surface and a road edge and that, at a long distance, the light beams are narrowed. Therefore, light beams not appearing at a long distance are also illuminated on the screen at a short distance, and there is given rise to a difference between that position of the optical axis on the screen 10 meters ahead which is calculated on the basis of the illuminating pattern on the screen 3 meters ahead, and the actual position of the optical axis.

In addition, the measurement of the optical axis is conventionally carried out on a presumption that a light source of the headlight (i.e., a filament) is positioned in a predetermined position. However, there are cases where the actual position of the light source deviates from a set position due to an initial running-in period of suspension members, variations in the pneumatic pressures of tires, assembling inaccuracies of related parts, or the like. This deviation also gives rise to a difference between that position of the optical axis 10 meters ahead which is calculated on the basis of the position of the optical axis on the screen 3 meters ahead, and the actual position of the optical axis.

OBJECT AND SUMMARY OF THE INVENTION In view of the above-described problems, this invention has an object of providing a method of measuring an optical axis of a headlight wherein light beams with directional vectors which have no relation with the longdistance illuminating pattern are decayed, and wherein the optical axis of the headlight can be accurately measured on the basis of the illuminating pattern at a short distance.

In order to attain the above-described object, this invention is a method of measuring an optical axis of a headlight comprising the steps of disposing a lattice member in front of the headlight, the lattice member having a plurality of longitudinally elongated lattice holes which are arranged in a form of a matrix, and measuring an illuminating pattern of light beams which are transmitted through the lattice member, thereby measuring the optical axis of the headlight.

In one preferred mode, the lattice member may be made of a plurality of horizontal and vertical plates which are formed into a latticework. Or else, it may be an aggregation of a plurality of cylindrical members.

Since the lattice holes extend in the longitudinal direction, they do not allow the transmission of the light beams having directional vectors which are largely inclined towards the vertical and the horizontal directions and hence having no relation with the long-distance illuminating pattern. As a result, the illuminating pattern of the light beams which have been transmitted through the lattice member is similar to that of the long-distance illuminating pattern. It is therefore possible to accurately measure the optical axis of the headlight on the basis of the shortdistance illuminating pattern of the light beams transmitted through the lattice member.

The illuminating pattern of the light beams to be transmitted through the lattice member is formed by illuminating each of illuminating regions divided into the form of a matrix by the lattice holes with the light beams passing therethrough. In an illuminating region which corresponds, among all lattice holes, to a particular lattice hole having an extended hole axis line which passes through the light source of the headlight, the light beams are illuminated over the entire surface of the illuminating region, resulting in a maximum illuminated area. On the other hand, in an illuminating region corresponding to a lattice hole which coincides with the optical axis of the headlight, the illuminance becomes maximum.

Therefore, even if the position of the light source is off the set position due to the initial running-in period of the suspension members, variations in the pneumatic pressures of tires, or the like, the position of the light source can be located or inferred from the illuminating region of maximum illuminated area. Out of this position of the light source and the position of the optical axis which is located from the illuminating region of maximum illuminance, the inclination angle of the optical axis is calculated. Thereafter, by adjusting the optical axis of the headlight depending on the deviation between this inclination angle and the set inclination angle of the optical axis, the long-distance displacement of the optical axis can be reduced to the best extent possible.

Further, even without the calculation of the inclination angle of the optical axis as described above, it is possible to match the inclination angle of the optical axis to the set inclination angle by adjusting the optical axis such that the illuminating region of maximum illuminance falls within a predetermined range, around the illuminating region of maximum illuminated area.

In this case, if each lattice hole is inclined so as to have the same inclination angle as that of the set inclination angle of the optical axis, the extension line of the hole axis of a particular lattice hole which coincides with the optical axis will pass through the light source when the inclination angle of the optical axis becomes the set inclination angle. Therefore, by making adjustments of the optical axis such that the illuminating region of maximum illuminated area comes into coincidence with the illuminating region of maximum illuminance, the inclination angle of the optical axis coincides with the set inclination angle.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects and the attendant advantages of this invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: Fig. 1 is a diagram showing an embodiment of an apparatus to be used in this invention method; Fig. 2 is a perspective view of a lattice member; and Figs. 3 and 4 are diagrams explaining the operations, respectively.

DETAILED DESCRIPTION OF THE INVENTION With reference to Fig. 1, numeral 1 denotes an optical axis measuring apparatus which is positioned at a short distance of about 3 meters ahead of a headlight B of an automobile A which is stopped at a predetermined position.

This apparatus comprises a lattice member 3 which is provided, as shown in Fig. 2, with a plurality of lattice holes 2 which extend in the longitudinal (i.e., forward and backward) direction, a screen 4 which is disposed in front (on an opposite side of the headlight) of the lattice member 3 and is made up of ground glass or the like, and a CCD camera 5 which is disposed in an opposing manner in front of the screen 4. A picture signal from the camera 5 is input into a computer 6 which contains therein a picture processing circuit. A servo driving unit 8 which has a pair of tools 7, 7 for adjusting the vertical and horizontal directions of the headlight B is controlled by the computer 6 to adjust the optical axis of the headlight B.

The axial length of the lattice holes 2 of the lattice member 3 is set to such a length of 30cm - 60cm, for example, as will be sufficient to decay those light beams which have directional vectors largely inclined in the vertical and horizontal directions and hence have no relation with the long-distance illuminating pattern.

The illuminating pattern, on the screen 4, of the light beams which have been transmitted through the lattice member 3 will be the one in which the light beams passing through each lattice hole 2 are illuminated on each of the illuminating regions as divided into the form of a matrix corresponding to the lattice holes 2. More detailed explanation is made taking, as an example, an illuminating pattern in the vertical section. In case the hole axis of each lattice hole 2 is horizontal, the transmitted light is illuminated on that entire surface of an illuminating region a which corresponds to a particular lattice hole 2 of the same level as the light source B1 of the headlight B, as shown in Fig. 3. The illuminated area decreases as the region becomes away from the region a.The illuminance, on the contrary, becomes maximum at an illuminating region b corresponding to a lattice hole which coincides with the optical axis B2 of the headlight B. The illuminance decreases as the region becomes away from the region b. The vertical widths of the hatched portions in Fig. 3 represent the illuminated area and the horizontal widths thereof represent illuminance.

The illuminating pattern on the screen 4 is pictured by the camera 5, and the pictured images are processed by the computer 6 to obtain a position of the illuminating region a in which the illuminated area becomes maximum and a position of the illuminating region b in which the illuminance becomes maximum. It is thus possible to locate or infer the position of the light source B1 from the illuminated region a as well as the position of the optical axis B2 from the illuminated area b. From thus located position of the light source B1 and the position of the optical axis B2, it is possible to calculate the inclination angle 9 of the optical axis B2 through geometric calculations.Thereafter, by obtaining a deviation of the inclination angle e from a set inclination angle eS of the optical axis, the driver unit 8 is driven depending on the deviation to adjust the optical axis B2 until it becomes e s When the inclination angle of the optical axis B2 becomes 6 sf the illuminating region of maximum illuminance is transferred to a region as shown by c in Fig. 3.It means that the illuminating region of maximum illuminance is located within a predetermined range around the area a depending on e5. Therefore, it is possible to adjust the inclination angle of the optical axis to e S also by adjusting the optical axis through a feedback control such that the illuminating region of maximum illuminance is transferred within this predetermined range.

Now, another embodying example is explained in which each of the lattice hole 2 is inclined so that the hole axis has the same inclination angle as the set inclination angle As shown in Fig. 4, when the inclination angle of the optical axis B2 coincides with gs the extension line of the hole axis of a lattice hole 2 through which the optical axis B2 passes, passes through the light source B1. As a result, both the illuminated area and the illuminance of the illuminating region d corresponding to that particular lattice hole 2 become maximum.Therefore, if the inclination angle of the optical axis is adjusted such that the illuminating region of maximum illuminance coincides with the illuminating region of maximum illuminated area, the inclination angle of the optical axis can be adjusted to the set inclination angle e S If the inclination angle of the optical axis is made to coincide with the set inclination angle as described above, the optical axis moves in parallel while keeping the set inclination angle even if the position of the light source B1 deviates. Therefore, the deviation of the optical axis from its normal position can be kept within the deviation in the position of the light source B1 irrespective of the distance from the headlight B.

As can be seen from the above description, according to the invention of claim 1, it is possible to decay by the lattice member the light beams having directional vectors which have no relation with the long-distance illuminating pattern. Therefore, the optical axis can be accurately measured on the basis of the short-distance illuminating pattern of the light beams which have been transmitted through the lattice member. Furthermore, as the invention of claim 2, it is possible, by measuring the illuminated area and the illuminance which correspond to each lattice hole of the lattice member, to obtain the position of the light source as well as the position of the optical axis.

It therefore becomes possible to measure the inclination of the optical axis which is not known from the position of the optical axis alone. Accordingly, as the inventions of claims 3 through 5, it is possible to adjust the optical axis to a predetermined set angle regardless of the deviation in the position of the light source. It therefore has an effect in that the errors in the position of the long-distance optical axis can be eliminated to the best extent possible. It is readily apparent that the abovedescribed has the advantage of wide commercial utility. It should be understood that the specific form of the invention hereinabove described is intended to be representative only, as certain modifications within the scope of these teachings will be apparent to those skilled in the art.

Accordingly, reference should be made to the following claims in determining the full scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A method of measuring an optical axis of a headlight comprising the steps of: disposing a lattice member in front of the headlight, said lattice member having a plurality of longitudinally elongated lattice holes which are arranged in a form of a matrix; and measuring an illuminating pattern of light beams which are transmitted through said lattice member, thereby measuring the optical axis of the headlight.

2. A method of measuring an optical axis of a headlight according to claim 1, wherein measurement of said illuminating pattern is performed by measuring an illuminated area and an illuminance of light beams transmitted through said each lattice hole at each of illuminating regions which are divided into a form of a matrix by said lattice holes, and wherein a position of a light source of the headlight is located by an illuminating region of maximum illuminated area and a position of an optical axis of the headlight is located by an illuminating region of maximum illuminance

3.A method of adjusting an optical axis of a headlight comprising the steps of: disposing a lattice member in front of the headlight, said lattice member having a plurality of longitudinally elongated lattice holes which are arranged in a form of a matrix; measuring an illuminated area and an illuminance of light beams to be transmitted through said lattice holes at each of illuminating regions which are divided into a matrix by each of said lattice holes; locating a position of a light source from an illuminating region of maximum illuminated area and a position of an optical axis of the headlight from an illuminating region of maximum illuminance; calculating an inclination angle of said optical axis from the located position of said light source and the position of said optical axis; and adjusting said optical axis depending on a deviation between the calculated inclination angle and a set inclination angle.

4. A method of adjusting an optical axis of a headlight comprising the steps of: disposing a lattice member in front of the headlight, said lattice member having a plurality of longitudinally elongated lattice holes which are arranged in a form of a matrix; measuring an illuminated area and an illuminance of light beams to be transmitted through said lattice holes at each of illuminating regions which are divided into a matrix by each of said lattice holes; and adjusting said optical axis of the headlight such that an illuminating region of maximum illuminance falls within a predetermined range around an illuminating region of maximum illuminated area.

5. A method of adjusting an optical axis of a headlight according to claim 4, wherein each of said lattice holes is inclined so that said lattice holes have an inclination angle equal to a set inclination angle of said optical axis and wherein said optical axis of the headlight is adjusted so that said illuminating region of maximum illuminance comes into coincidence with said illuminating region of maximum illuminated area.

6. A method of measuring or adjusting an optical axis of a headlight substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

7. Apparatus for measuring or adjusting an optical axis of a headlight including: a lattice member for positioning in front of the headlight, said lattice member having a plurality of longitudinally elongated lattice holes which are arranged in a form of a matrix; and means for measuring an illuminating pattern of light beams which are transmitted through said lattice member.