JPH01159904A - Projector type head light - Google Patents

Abstract

PURPOSE: To reduce a weight and a cost, and to improve the effective utilization rate of luminous flux and durability, by arranging the prism face of a Fresnel prism lens toward the front and by covering its front with a transparent board- like cover. CONSTITUTION: A Fresnel prism lens 14, in which a meridional image surface is positioned on a cut line of a shade 4, is installed, and the prism face is faced to the floodlighting direction. A front cover 15 of a transparent plain front lens type is installed, covering the front of the Fresnel prism lens 14, and besides, an inner panel 16 for shielding excessive light is installed. Consequently, incident light into the prism element, shown by arrows k1 to k3 , is refracted as shown by I1 to I3 , and the whole thereof floodlights forward as shown by m1 to m3 , to thereby improve the effective utilization rate of the luminous flux.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projector type vehicle headlamp.

[Conventional technology]

Automobile headlights must have a light distribution pattern that brightly illuminates the area in front of the vehicle's own lane and does not dazzle oncoming vehicles.

A projector-type automobile headlamp has been proposed as a headlamp that has light distribution characteristics that meet the above requirements, has a simple lens configuration, and can be made compact in overall size. As the latest technology regarding this projector type headlamp, for example, Japanese Patent Laid-Open No. 58-209801 is known.

FIG. 3 shows the above-mentioned known projector type headlamp. The headlight of this known example is provided with a shell-shaped reflector, and the axial cross section of the inner reflective surface of this reflector each forms a part of an ellipse, and the eccentricity of the ellipse is perpendicular to the axial direction. In a vehicle headlamp increasing from the longitudinal section towards the axially horizontal longitudinal section, the focal point 105 of the elliptical portion 101° 102 of every axial section is also the elliptical portion 101 of every axial section. .1.02 corresponding vertex 104
are configured to match.

101 is an outer focus of the ellipse 102, 110 is a light shielding plate-like dimmer, 112 is an outer focus of the ellipse 101, and 113 is a lens.

FIG. 4 is a plan view schematically depicting an example of this type of projector type headlamp, FIG. 5 is a side view, and FIG. 6 is a front view.

1 is a concave mirror, and F is its focal point. The light source bulb 2 is provided so that the filament is located near the focal point F mentioned above.

A convex lens 3 is provided to share the optical axis Z with the concave mirror 1 described above.

4 indicates the meridional image plane of the convex lens 3, and the light emitted from the light source and reflected by the concave mirror 1 is incident on this meridional image plane.

The above incident light is modulated by the convex lens 3 and is directed forward (
4 and 5).

When a screen is provided near the meridional image plane and the light distribution pattern is shown as an isoluminance curve, it becomes as shown in FIG.

H-H is a horizontal line on the screen, and V-V is also a vertical line.

As shown in FIGS. 4 to 6, a shade 4 having an edge along the meridional image plane is provided. Specifically, as shown in 4a shown in FIG. 6, a cut line 4a is formed so as to recede from the meridional image plane i-J. FIG. 8 shows how the light distribution pattern described above (FIG. 12) and the shade 4 overlap. As shown in FIG. 13, the upper half of the light beam passes through. Although most of the lower half is blocked, light is allowed to pass through the portion corresponding to the cut line 4a.

As the partially covered light beams as described above are focused on the meridional image plane l-j and intersect with each other, the light beams projected in front of the headlight have a pattern that is an inversion of the one shown in Figure 8. form. FIG. 9 is an explanatory diagram showing the general shape of a light projection pattern using isoluminance curves on a screen provided in front of the headlight.

[Problem that the invention seeks to solve]

As shown in FIGS. 4 and 5, the convex lens of the projector type headlamp has a short focal length and a large thickness. Therefore, the cost of lens components is high, and the weight of the entire headlamp is also increased.

In order to eliminate these problems, as shown in Figure 1O,
There is an example in which the convex lens is a Fresnel prism lens 13.

FIG. 11 is an enlarged optical path diagram of a part of the Fresnel prism lens 13.

When the light beam in the range of angle 01 shown in the figure is incident on the Fresnel prism element, the light beam in the range of θ3 that is incident on the spherical part of the prism is projected forward as shown by the arrow (A), but the stepped part of the prism The luminous flux in the range of θ2 (shown with spots) that is incident on becomes an invalid component.

Although it is possible to eliminate the above-mentioned invalid components by improving the shape of the prism, it is difficult to produce such a prism lens industrially.

The reason why the conventional projector type headlamp (FIG. 10) has its prism surface facing the light source bulb side is as follows.

(i) If the prism surface faces forward in the light projection direction,
This is because the optical performance is easily impaired due to dirt or getting wet with rain, and (ii) it is also easily damaged.

Conventionally, various types of lighting equipment such as signal lights using Fresnel prisms have been installed with the prism surface facing the light source side (that is, toward the rear in the light projection direction) for reasons (i) and (ii) above. It had become a custom.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a projector-type headlamp that has a high luminous flux efficiency, is lightweight, low cost, and highly durable.

[Means for solving problems]

A projector type headlamp according to the present invention created to achieve the above object has a convex lens constituted by a Fresnel prism lens, the prism surface of the Fresnel prism lens facing forward, and A transparent plate-like cover is provided to cover the front of the Fresnel prism lens. This cover may be so-called transparent, and it does not prevent the prism elements from being arranged.

[Effect]

According to the above configuration, ◎Since the convex lens is a Fresnel prism lens, it is lightweight;
◎Since the prism surface of the Fresnel prism lens faces forward, the effective utilization of the luminous flux is high.Moreover, ◎A cover is provided on the front of the lens, so the prism surface does not get dirty, wet, or damaged. There is no danger.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of a projector type headlamp according to the present invention, in which 1 is a concave mirror, 2 is a light source bulb,
4 is a shade.

The projector type headlight of this example is provided with a Fresnel prism lens 14 whose meridional image plane is positioned at the cut line (upper edge in the figure) of the shade 4, and whose prism surface is directed in the light projection direction (left side in the figure). ).

A transparent plain front lens-shaped front cover 15 is provided to cover the front surface of the Fresnel prism lens. 16 is
This is an inner panel to block excess light.

FIG. 2 is an enlarged optical path diagram of a part of the Fresnel prism lens 14.

The light incident on the prism element as shown by the arrows kl + k2 + k3 is refracted as shown in QI + flZr Q3, and all of it (ignoring reflection, absorption, and scattering in extremely small parts) is projected forward as shown in ITN, m2 + m3. is,
High effective utilization of luminous flux.

〔Effect of the invention〕

The projector type headlamp of the present invention is lightweight, inexpensive, has a high luminous flux efficiency, and has excellent durability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a projector type headlamp according to the present invention, and FIG. 2 is an optical path diagram showing the effects of the above embodiment. 3 to 9 are diagrams explaining the principle of a projector type headlamp. FIG. 10 is a sectional view of a conventional projector type headlamp, and FIG. 11 is an optical path diagram for explaining problems in the conventional example. 1... Concave mirror (reflector), 2... Light source bulb, 3-convex lens, 4... Shade, 13.14... Fresnel prism lens, 15... Front cover, 16... Inner panel.

Claims (1)

[Claims] 1. A light source bulb is installed near the focal point of the reflecting mirror, and the light emitted from the light source bulb is reflected by the reflecting mirror and focused near the member having the cut line, and the light source is In a projector-type headlamp that projects reflected light forward, (a) the convex lens is constituted by a Fresnel prism lens, and (b) the prism surface of the Fresnel prism lens is used for projection of the headlamp. A projector-type headlamp, oriented in the light direction, and (c) comprising a transparent plate-like cover covering the front of the Fresnel prism lens.