JPH10269804A - Light source and headlamp and headlight for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the occluded feeling caused by visual field limitation, relax the tension, and reduce the glare against the illumination light at the center section of an optical axis by reducing the intensity of the bright-place photometric quantity of emitted light from the center section to the periphery section of the optical axis, and increasing the ratio γ of the dark-place photometric quantity against the bright-place photometric quantity of the emitted light. SOLUTION: A real image 5 is the optical image of a luminescent face 1 by a convex lens 2, the convex lens 2 is made of a single lens, and intensity is reduced from the center section toward the periphery of an optical axis as the general feature of the optical image. When the γ value is increased from the center section toward the periphery section of the optical axis for the illumination light decreased with the intensity from the center section toward the periphery of the optical axis, the visual field limited by the illumination light is expanded. The γ value of the emitted light from the center section of the optical axis is set to 1.5 or below, and glare is hardly felt. The γ value of the emitted light from the periphery of the optical axis is set to 1.5 or above, and the visual field can be thereby expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source, a vehicle headlamp, and a headlight having a wide field of view formed by illuminating light and having less glare.

[0002]

2. Description of the Related Art Conventionally, a halogen bulb has been used as a light source for a vehicle headlamp. The vehicle headlight is configured in combination with an optical system arranged so as to surround the halogen bulb, and the intensity of the illumination light is highest at the center of the optical axis, and the intensity sharply decreases toward the periphery of the optical axis. It is designed to be. The angular characteristics of the intensity of the illumination light are defined in Japanese Industrial Standard (JIS) D5500.

When a vehicle equipped with a vehicle headlight based on this regulation is actually driven on a road at night, the vehicle is located in front of the vehicle which is illuminated at the center of the optical axis where the intensity of photopic light measurement is high. There is no problem in visually recognizing obstacles that occur. However, there is a problem in that information such as a road shoulder illuminated in the vicinity of the optical axis cannot be obtained sufficiently because the intensity of photopic light measurement light in the illumination light is insufficient. This increases the sense of tension to prepare for pedestrians and vehicles to jump out, and has a high blocking feeling due to the impression that the field of view is limited within the range illuminated by the illumination light from the vehicle headlights. there were.

[0004]

In recent years, studies have been made to use a high-intensity discharge lamp (hereinafter, HID lamp) as a light source for a vehicle headlamp instead of a halogen bulb (for example, Japanese Patent Application Laid-Open No. HEI 3-110748). ). Since the HID lamp has a higher energy conversion efficiency than a halogen bulb, it has an advantage that the total photopic photometric amount can be increased.

[0005] Further, by appropriately selecting the lamp enclosing material, the spectral composition of the illuminating light can be made different from that of a halogen bulb. The ratio γ of the scotopic light measurement amount to the amount can be increased. Therefore, by using an HID lamp that generates a radiated light having a larger γ value (higher correlated color temperature) than the radiated light of the halogen bulb, the intensity sharply increases from the center of the optical axis to the periphery based on the Japanese Industrial Standard. A vehicle headlight that can be reduced can be configured.

In FIG. 3, black circles indicate the calculated value of γ based on the spectral distribution of black body radiation, and crosses indicate the standard light source A (correlated color temperature of 2854K) defined by the International Commission on Illumination.
Of the standard light source D defined by the International Commission on Illumination, the correlated color temperature of 5000K, 5500K,
Γ values for 6500K and 7500K. FIG.
As shown in (1), for the standard white light source, the correlated color temperature and the γ value have a corresponding relationship.

Although the gaze position of the driver is not generally determined with respect to the visual space illuminated by the vehicle headlamp, the illuminated surface illuminated by the central portion of the optical axis where the intensity of the illuminating light is the highest is the most. It should be easy to get visual information. Therefore, it is considered that the visual target illuminated by the central part of the optical axis is mainly watched. FIG. 4 shows the relationship between the surface to be illuminated by the illumination light and the driver's line of sight for the single-lamp type vehicle headlamp.

In FIG. 4, reference numeral 40 denotes a vehicle headlamp;
Is the driver, 42 is the optical axis of the vehicle headlamp, 43 is the illuminated surface by the central part of the optical axis, 44 is the illuminated surface by the peripheral part of the optical axis, 45
Is the driver's line of sight. Here, the optical axis peripheral portion 44 is illuminating light in a range equal to or larger than the limit of the angle formed with respect to the optical axis defined in the horizontal direction in Japanese Industrial Standard D5500 (for example, 12 degrees left and right for 3 degrees below).

The line of sight 45 of the driver 41 is the headlight 4 for the vehicle.
0 is directed to the illuminated surface 43 by the central part of the optical axis 42. At this time, the illuminated surface 44 due to the peripheral portion of the optical axis having lower illuminance than the illuminated surface 43 due to the central portion of the optical axis is to be observed by the driver's peripheral vision. Due to the structure of the human eye, the light receiver has a cone and a rod that works even if the amount of incident light is smaller than the cone, and the composition ratio between the cone and the rod is the optical image of the visual target at the center of the line of sight Is largest at the retinal position projected by the eyeball optical system (more cones), and becomes smaller as the distance from the line of sight at the retinal position where the visual target of peripheral vision is projected (more rods).

The output of the cone is determined by photopic light intensity.
The output of the rod can be described by scotopic photometry. In the case of the observation conditions as shown in FIG. 4, the visual target on the illuminated surface 44 by the optical axis peripheral portion is projected as an optical image of a small light amount onto the retina region including many rods. For this reason, the condition of the brightness of the illuminated surface illuminated by the periphery of the optical axis is easily determined by the rod output.

Therefore, even if the photopic measurement light amount is the same, γ
The illumination light of the vehicle headlight using the HID lamp that emits light having a large value has an effect that the illuminated surface around the optical axis appears brighter than the illumination light of the vehicle headlight using the halogen bulb. . That is, the feeling of obstruction that the field of view is limited by the headlight is reduced. In addition, He, Rea, Bierman and B., found that using a lamp with a large γ value can shorten the viewing time of a viewing target illuminated by the periphery of the optical axis such as the road shoulder.
Experimentally confirmed by Bullough (1995 IESNA Proceedings, p. 236-
57). In other words, the sense of tension for preparing for a pedestrian or vehicle jumping out is reduced.

However, in actual road driving,
When the illumination light at the center of the optical axis, which has a high intensity, out of the illumination light of the oncoming vehicle headlamp enters the field of view, glare is felt. At this time, it is known that glare increases when a light source having a large γ value of illumination light (high correlated color temperature) is directly seen (for example, Yano et al., Journal of the Illuminating Engineering Institute, Vol. 77, No. 2).
From page 96 to page 303). For this reason, as the γ value of the emitted light of the lamp is larger, the illumination light at the center of the optical axis of the vehicle headlamp using the lamp causes discomfort during driving of an oncoming vehicle, and the vehicle is driven safely. In addition, there was a problem that there was an obstacle.

[0013]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention reduces the intensity of photopic light measurement of radiated light from the central part of the optical axis to the peripheral part and reduces the intensity of the radiated light. The ratio of the photopic photometric light intensity to the photopic photometric light intensity (hereinafter, referred to as
γ) is increased.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention reduces the intensity of photopic light measurement of radiated light from the central part of the optical axis to the peripheral part, and also provides the scotopic light measurement light intensity with respect to the photopic measured light quantity of the radiated light. By increasing the ratio γ, the reduction of the feeling of obstruction and the relaxation of the tension due to the restriction of the visual field, and the reduction of the glare with respect to the illumination light at the center of the optical axis can be achieved at the same time.

By reducing the γ value at the center of the optical axis (lowing the correlated color temperature), the glare when the illumination light is directly viewed can be reduced. Also, by increasing the γ value around the optical axis, the brightness around the illuminated surface can be increased under the observation conditions as shown in FIG.

Note that the γ value is large but the intensity is small in the vicinity of the optical axis, so that even if the light is directly seen, no glare is felt.

FIG. 1 shows the configuration of an experimental apparatus in which the above effects have been confirmed. In FIG. 1, 1 is a light emitting surface,
2 is a convex lens, 3 is a filter a, 4 is a filter b, 5 is a real image, 6 is a diffuse transmission surface, and the optical axis is shown by a dashed line.
The light emitting surface 1 was configured by combining an HID lamp and an opening. The convex lens 2 was constituted by a single lens.

The filter a3 is arranged on the lower side of the paper from the optical axis, and the filter b4 is arranged on the lower side of the paper from the optical axis. The filter b4 has a characteristic of selectively transmitting a wavelength band around 520 nm, and the filter a3 is made of a material having a characteristic of selectively transmitting a wavelength band of 600 nm or more. The real image 5 is an optical image of the light emitting surface 1 by the convex lens 2. As a general property of an optical image formed by a single lens, the intensity decreases from the center of the optical axis to the periphery. In the light emitting surface 1, A,
O and B correspond to A ', O', and B 'of the real image 5, respectively. The light transmitted through the filter a3 is focused on the portion A ',
Light transmitted through the filter b4 is condensed on the portion B ', and O'
Light transmitted through both the filter a3 and the filter b4 is condensed on the portion at an equal ratio.

The real image 5 was diffused and transmitted by the diffusion transmitting surface 6. The observer observed the real image 5 through the diffuse transmission surface 6. The corresponding points on the diffuse transmission surface 6 of A ′, O ′, and B ′ of the real image 5 as viewed from the observer are A ″, O ″,
B ''. The optical density of the filter b4 was adjusted so that the photopic luminance at the points A ″ and B ″ was 0.020 cd / m 2. This photopic luminance value is 28 m due to illumination light whose angle with respect to the optical axis is 12 degrees in the horizontal direction in a vehicle headlamp satisfying Japanese Industrial Standard D5500.
This corresponds to the photopic luminance of the illuminated surface when illuminating a road surface with a reflectance of 10% in front (perceived distance of a lane marking on a straight road at a running speed of 50 km / h).

On the other hand, the scotopic luminance value is 0.014 scotopic cd / m2 (γ = 0.7) in the A ″ portion and 0.052 scotopic cd / m2 (γ) in the B ″ portion. = 2.6). The brightness was compared between point A ″ and point B ″ while the observer was gazing at point O ″ with the surroundings being dark. As a result, it was evaluated that the point B ″ was brighter. In other words, for illumination light whose intensity decreases from the center of the optical axis to the periphery, it can be confirmed that by increasing the γ value from the center of the optical axis to the periphery, the field of view limited by the illumination light can be expanded. Was.

In order to prevent glare of illumination light, the value of γ in light emitted from the center of the optical axis is set to 1.5 or less. By using such synchrotron radiation, the value of γ is reduced as shown in FIG.
Compared to the high (γ = 2.6) radiation light as in the part, the limit brightness of the glare can be 1.5 times or more, that is, the glare can be made hard to feel. Then, by setting the value of γ in the emitted light from around the optical axis to 1.5 or more,
The effect of expanding the field of view limited by the illumination light can be provided. In the present invention, since the intensity is reduced from the central part to the peripheral part of the optical axis, the radiated light from the peripheral part of the optical axis does not feel glare even if the value of γ is high.

The present invention can also be configured such that the wavelength of monochromatic light is changed from the central part of the optical axis to the peripheral part using, for example, a spectroscope. In order to be able to identify the color of the visual target in the visual target on the illuminated surface in the center of the optical axis,
The light is composed of a plurality of monochromatic lights. When white light is used as the illumination light, the condition that the value of γ is 1.5 or less from FIG. 3 corresponds to 3500K or less in white light.

In order to construct the light source as described above, at least a part of the components of the optical system disposed so as to surround the lamp has wavelength selectivity in the reflectance or transmittance, and is located at the center of the optical axis. The optical system may be designed so as to obtain emitted light having a different spectral composition from the peripheral part.

FIG. 2 is a block diagram of an embodiment of the light source according to the present invention.
Shown in In FIG. 2, 11 is a lamp, 12 is a reflecting mirror,
13 is a lens. In the first embodiment, the lamp 1
No. 1 uses a small HID lamp and has a size close to a point light source, and facilitates the following optical system design. The optical system in each of the embodiments is a parabolic reflector 12 that is axially symmetric with respect to the optical axis.
And a lens 13, and are arranged so that the rear surface of the lamp 11 is surrounded by the reflecting mirror 12.

With respect to the optical system arranged as shown in FIG. 2, ray tracing was performed for each angle θ formed by the light emitted from the lamp with respect to the optical axis. As a result, the angle θ is 0 degree, 90 degrees
At 135, 135 and 180 degrees, the emitted light was illumination light at the center of the optical axis, and at 45 degrees, it was illumination light at the periphery of the optical axis. Therefore, when the angle θ is 45 degrees or less, the lamp 1
Since the light 1 is directly incident on the lens 13, the illumination light around the optical axis is determined by the spectral radiant energy distribution of the lamp 11 and the spectral transmittance of the lens 13.

On the other hand, the illumination light at the center of the optical axis
From the irradiating light directly incident on the lens 13 and the reflecting mirror 12
The light is mixed with light that is incident on the lens 13 after being reflected by the lens 13.

In the first embodiment of the present invention, γ
A lamp 11 that emits radiation having a spectral radiation energy distribution with a high value (high correlated color temperature), and a reflecting mirror 12 having a wavelength selectivity such that the reflectance is high mainly in a wavelength band of 560 nm or more. Combine.

With such a configuration, since the γ value can be reduced by the reflecting mirror 12, the γ value of the illumination light at the central portion of the optical axis can be made smaller than that at the peripheral portion of the optical axis. .

Although the case where the reflectance of the reflecting mirror 12 has wavelength selectivity has been described with reference to FIG. 2, at least a part of the material constituting the optical system is made of a material having wavelength selectivity. Thereby, a similar effect can be obtained.
For example, it can be realized by arranging an optical filter having a different spectral transmittance or a reflective thin film having a different spectral reflectance before and after the lens 13 according to the degree of separation from the optical axis.

In the light source according to the present invention having the above-described structure, the glare is hard to be felt even when the central part of the optical axis having a large intensity is directly seen, and the illuminated surface around the optical axis is felt bright.

When the light source of the present invention is a headlamp for a vehicle, the driver of an oncoming vehicle is less likely to feel glare, so that traffic safety is improved. In addition, since the peripheral portion of the headlight illumination light is bright, the feeling of obstruction whose visual field is restricted by the illumination light is reduced, and the sense of tension for preparing for a pedestrian or a vehicle to jump out can be reduced.

By making the light source of the present invention a portable headlight for mine lighting, for example, it is difficult for co-workers to feel glare, so that work safety is enhanced. In addition, since the feeling of obstruction that the field of view is limited by the illumination light is reduced, the feeling of anxiety in the closing work is reduced.

[0033]

As described above, according to the present invention, the glare is hard to be felt even when the central portion of the optical axis having a large intensity is directly viewed, and the illuminated surface around the optical axis is felt bright. Headlights for vehicles that expand the field of view
A headlight can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an observation experiment confirming the effect of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a relationship diagram between a correlated color temperature of a standard white light source and a ratio γ of scotopic photometric light intensity to photopic photometric light intensity.

FIG. 4 is a diagram showing the relationship between the illuminated surface of a one-light vehicle headlamp and the driver's line of sight;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Emission surface 2 Convex lens 3 Filter a 4 Filter b 5 Real image 6 Diffuse transmission surface 11 Lamp 12 Reflecting mirror 13 Lens

Claims (6)

[Claims] 1. The method according to claim 1, wherein the intensity of the photopic light measurement amount of the emitted light is reduced from the central portion of the optical axis to the peripheral portion, and a ratio of the photopic light measurement amount of the emitted light to the scotopic photometry light amount (hereinafter, referred to as "the photopic measurement light amount"). γ)
The light source characterized by having increased. 2. The value of γ in the emitted light at the center of the optical axis is set to 1.
2. The light source according to claim 1, wherein the value of [gamma] in the radiation light around the optical axis is 1.5 or more. 3. The light source according to claim 2, wherein the correlated color temperature of the radiated light at the center of the optical axis is white light of 3500 K or less. 4. A radiation element having a wavelength selectivity in the reflectance or transmittance of at least a part of components of an optical system arranged so as to surround a lamp, and having different spectral compositions between a central portion and a peripheral portion of an optical axis. 4. The light source according to claim 2, wherein light is obtained. 5. A vehicular headlamp having the light source according to claim 2. 6. A headlight having the light source according to claim 2.