JPS63309834A - Optical axis detector for automobile headlight or the like - Google Patents

Abstract

PURPOSE:To eliminates the need for a confronting mechanism and to obtain effects which remove an error in the positioning of the confronting mechanism by arranging a screen where a similar reduced light distribution pattern is projected at the focal length position of an optical lens. CONSTITUTION:An optical system is provided which allows a light distribution pattern at a distance D1 from an optical lens l with focal length (f) installed nearby an automobile headlight L, etc., to be reduced similarly and observed by the optical lens l, a half-mirror which is installed in front of the lens lat a specific angle to the optical axis of the lens, and the screen S2 where light from the headlight l reflected by the half-mirror is projected. Then the screen S2 is provided at the position of the focal length (f) of the lens l, and consequently even if the headlight L is moved in parallel to the optical axis of the lens l, the light distribution pattern on the screen S2 does not vary. This means that an optical axis inspecting device and the headlight L need not be confronted with each other. The optical axis is detected according to reflected light from this screen S.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical axis (optical central axis) detection device used in adjusting and inspecting the irradiation light distribution of automobile headlights, etc., and in particular, the present invention relates to an optical axis (optical center axis) detection device used for adjusting and inspecting the irradiation light distribution in automobile headlights, etc., and in particular, the present invention relates to an optical axis (optical central axis) detection device used for adjusting and inspecting the irradiation light distribution in automobile headlights, etc. It is designed to detect the optical axis.

[Conventional technology]

For observation of this type of irradiation light distribution, JIS-D-55
Standards have been established for the 00, which stipulates that the amount of light emitted must be observed within a range of 15 degrees left and right, a maximum of 3 degrees above, and a maximum of 4 degrees below from the optical center axis of the headlight at a distance of 10 meters in front of the headlight. ing. If this range were to be illuminated on a screen and observed, a wide space of about 5 m in horizontal width and about 10 m in depth would be required, and in practice it is often difficult to secure such a space, so it is not practical. As shown in Figure 4, the light distribution pattern is observed on a 2m wide screen placed 3m in front of the headlights, and
Using an optical system as shown in the figure, the light distribution pattern 10 m ahead is similarly reduced and observed. In Fig. 4, 1 is a car, 2 is a screen, 3 is a TV camera for the left side, 4 is a TV camera for the right side, 5 is a left and right screen partition plate, 6 is a left headlight, and 7 is a right headlight. There is. The screen 2 is installed 3 m in front of the headlights 6 and 7, and has a size of 2 m. With this configuration, the light rays emitted from the headlight 6°7 are directed to the screen 2.
The reflected light from the screen 2 is sent to the TV camera 3.
．． 4, perform image processing such as binarization, display on a monitor television (not shown), and observe the light distribution pattern. In addition, in Fig. 3, 8 is a headlamp, 9 is an optical lens,
10 is a half mirror, 111 is a screen, 12 is a television camera, 13 is a dustproof box, and 14 is an equivalent screen. The headlamp 8 is arranged close to the optical lens 9, and the light rays emitted from the headlamp 8 are directed to the surface of the half mirror 10 via the optical lens 9. For example, the half mirror 10 is 4
It is fixed with an inclination of 5". Therefore, about 50χ of the light rays incident on the half mirror 10 is specularly reflected on the mirror surface and heads towards the screen 11. The remaining light rays of about 50χ travel straight. This straight light, etc. In order to avoid the influence of dust, a non-reflective black coating is applied to the inner surface of the dustproof box 13 provided to protect the mirror 10 and screen 11 from dirt.The surface of the screen 11 is made of gypsum, etc. The screen has a reflection characteristic such that the reflected light from the surface of the screen 11 is proportional to the amount of light incident on the screen 11 regardless of the direction of observation.The reflected light from the surface of the screen 11 is
The light is diffusely reflected, but it is divided into a part that reaches the half mirror 10 and goes straight, and a part that is reflected toward the lens 9 side. Among these, the light beam that travels straight is received by the industrial television camera 12. Therefore, the light rays emitted from the headlight 8 are received by the television camera 12 via the lens 9 → mirror 10 → screen 11 → mirror 10 along the path shown by the solid arrow. The signal from the television camera is subjected to image processing such as binarization and displayed on a monitor television (not shown), and the light distribution pattern is observed.

[Problems to be solved by the invention]

However, the system shown in FIG. 4 has the following problems. (1) The irradiation light distribution pattern on the screen 3 m in front will be different from that 10 m in front because the headlights are not point light sources. (2) In principle, it is not possible to place a television camera for observation on the optical path of the headlights, so the observation must be done by looking down on the screen, resulting in a distorted light distribution pattern on the screen. Therefore, it is necessary to perform coordinate transformation in a later processing step to remove distortion. Although such problems can be solved by using an optical system as shown in FIG. 3, the optical system as shown in FIG. 3 has the following problems. (3) When observing with similar reduction, it is generally necessary to align the optical axis detection device and the headlight to be inspected (align the center axis of the optical axis detection device and the center of rotation of the headlight). be. In order to directly face them, there is a means for detecting the rotation center of the headlight to be directly faced through an optical lens to obtain a similar reduced light distribution pattern, and a means for moving the optical system according to the detected position. This also makes it expensive. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical axis detection device that eliminates the need for the above-mentioned facing mechanism and at the same time eliminates positioning errors of the facing mechanism.

[Means to solve the problem]

An optical lens with a focal length f that is installed close to an automobile headlamp, a half mirror that is installed in front of the optical lens at a predetermined inclination with respect to the optical axis of the lens, and this half mirror.
The screen is irradiated with the light from the headlight reflected by the optical lens, and the optical system is capable of similarly reducing and observing the light distribution pattern at the distance D1 from the optical lens. The distance between the optical lens and the screen is arranged to be equal to the focal length f of the optical lens.

[For use]

By arranging the screen that illuminates the similar reduced light distribution pattern at the focal length of the optical lens, the position of the similar reduced light distribution pattern can be changed only by the angular fluctuation, regardless of the parallel position shift of the headlight etc. Become.

【Example】

FIG. 2 is an explanatory diagram of the principle for obtaining a similar reduced light distribution pattern, and this principle will be explained below based on FIG. 2. The light rays incident on the point A on the virtual screen Sl serving as a reference plane are emitted from many points within the headlight (this is why it is not a point light source). For this reason, without an optical system, these light rays would not be concentrated on one point on any surface between the virtual screen S1 and the headlight, so a light distribution pattern similar to the light distribution pattern on the virtual screen S1 is No. This principle is such that all the rays that are incident on point A on virtual screen Sl at an arbitrary incident angle θ are incident on point B on screen S2, which is the observation surface, at a specific position, and points A and B are It takes advantage of the similar positional relationship. In order to derive these relationships in an easy-to-understand manner, this ray is extended toward the emission point, and the intersection point C between this extended line and a plane that includes one focal point of the lens l and is perpendicular to the optical axis of the lens l is considered. Since point C is on the focal plane of lens l, all rays emitted from this point travel in parallel after passing through lens l. That is, a ray of light that enters lens l from point C in parallel to the optical axis of lens l travels toward the other focal point. therefore,
A ray of light traveling toward point A on the virtual screen SI travels parallel to the ray of light behind the lens l and is incident on a point B on the screen S2. At this time, the position h of point A2 point B
Lh2 can be expressed as follows using the position X of point C. hl = (DI +f)・tanθ−x −−−
------------(11 By eliminating X from the first and second equations, the following third equation is obtained. In the third equation, the second term on the right side becomes 0" If the screen S2 is set at the distance D2 shown by the following 4th equation, the positions hl and h2 of points A and B are determined by the focal length f and the distance DI, as shown by the 5th equation.D2 Proportional to the constant, all the light rays incident on point A are incident on point B, and points A and B have a similar positional relationship. Therefore, the light distribution pattern at distance D1 passes through lens l, so that the light distribution pattern at distance D2 The light is similarly reduced and irradiated onto the screen S2 provided in the screen S2.The reduction ratio in this case is (f-D2)/f.The above is the principle for obtaining a similarly reduced light distribution pattern.Here The above-mentioned standard specifies observation at a distance of 10 meters in front, but the light distribution pattern at farther distances is not much different from that, or the light distribution pattern does not pose any problem in adjusting the optical axis, so it is possible to observe infinity. Considering the light distribution pattern in the distance, (4)
Since the equation can also be expressed as follows, if we set DI=■ and substitute it into equation (6), we get 02=f. This shows that it is sufficient to place the screen S2 at the position of the focal length f of the lens, and at this time, from equation (2), h2=ftan
θ−−−−−−−−−−−−−−−−−1−・−−−
-----------(71 holds true. FIG. 1 shows an explanatory diagram when the screen S2 is placed at the position of the focal length f of the lens. In FIG. 1,
When the headlight LL is installed on the optical axis of the lens l, the second
Thinking in the same way as the figure, among the rays emitted from the intersection C1 on the plane containing one focal point of lens E, the ray traveling parallel to the optical axis of lens 1 is on the plane containing the other focal point of lens 1.
That is, it enters the intersection B2 on the screen S2. In addition, the remaining light rays emitted from the intersection C1 pass through the lens l and proceed parallel to the light rays incident on the intersection B2, so for example, the light rays emitted at an angle θ to the optical axis point to the intersection on the screen S2. It is incident on B1, and the relationship h2=ftan θ is established. At this time, if we consider the headlight L2 that is moved parallel to the optical axis of the lens l, among the light rays emitted from the intersection C2 on the plane that includes one focal point of the lens l,
The light rays traveling parallel to the optical axis of the lens l enter an intersection B2 on the screen S2. In addition, the remaining light rays emitted from the intersection point c2 travel parallel to the light rays incident on the intersection point B2 after passing through the lens l. enters B1,
The relationship is h2=ftan θ. In this way, by providing the screen S2 at the focal length f of the lens l, the light distribution pattern on the screen S2 does not change even when the headlight is moved parallel to the optical axis of the lens. This shows that it is not necessary to directly face the optical axis inspection device and the headlight to be inspected. In addition, if you change the angle between the optical axis of lens β and the headlight, h2
- It goes without saying that the light distribution pattern changes due to the relationship between θ and θ.

【Effect of the invention】

According to this invention, by arranging the screen that irradiates the similar reduced light distribution pattern at the focal length of the optical lens, the position of the similar reduced light distribution pattern can be changed in angle regardless of the parallel positional deviation of the headlight. Therefore, it is possible to obtain a device that adjusts or inspects the angle of a headlight without directly facing the headlight so that the headlight is located at a constant position with respect to the optical axis detection device.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the principle of the apparatus according to the present invention, FIG. 2 is an explanatory diagram of the principle for obtaining a similar reduced light distribution pattern, FIG. 3 is a block diagram of the apparatus for observing a similar reduced light distribution pattern, and FIG. 4
The figure shows a schematic configuration diagram of a conventional light distribution adjustment system.

Claims (1)

[Claims] An optical lens with a focal length f that is installed close to an automobile headlamp, a half mirror that is installed in front of the optical lens at a predetermined inclination with respect to the lens optics, and a mirror that is reflected by the half mirror. The optical system includes a screen that is irradiated with light from a lamp or the like, and allows the light distribution pattern at the distance D1 to be similarly reduced and observed from the optical lens, and the optical axis is determined based on the light reflected from the screen. 1. An optical axis detection device for an automobile headlamp, etc., characterized in that the distance between the optical lens and the screen is set equal to the focal length f of the optical lens.