Lamp device for a vehicle having a free curved surface and a lens without a prism

A lens has a concave shape or a convex shape in either vertical cross section or transverse cross section. Thereby light passing through the lens is largely refracted and the interior is harder to be seen even if a prism is not formed. As a result, there is no need to give a finish more than optical performance required for reflection to the front surface of the reflecting surface of a reflector, which is for the purpose of enhancement of its appearance, and thereby the machining work is simpler than the conventional way. Further, since the lens has a flat shape in either vertical cross section or transverse cross section, the lens is easily polished when it is made of glass, which is excellent in manufacture of the lens.

FIELD OF THE INVENTION

The present invention relates to a lamp device for vehicle such as a vehicle headlamp and a vehicle fog lamp for illuminating ahead of a vehicle. More particularly, this invention relates to the lamp device for vehicle with a light distribution function imparted mainly to a reflector side.

BACKGROUND OF THE INVENTION

Lamp device for vehicles lately have a light distribution function imparted to a reflector side by shaping a reflecting surface of the reflector as a free curved surface. The latest lamp device for vehicles use so called permeable lens as a lens and have an outer cover function in the lens side. This permeable lens is not provided with a prism for light distribution, so that light passes through the lens as it is without refraction. That is, the permeable lens is formed of a plate-like (flat plate or curved plate) light transmitting member such as only a simple plate glass.

In the conventional lamp device for vehicles, however, the internal reflecting surface of the reflector is clearly seen through the permeable lens from the outside. Therefore, the conventional lamp device for vehicles require giving a finish more than optical performance required for reflection to the reflecting surface of the reflector, which is for the purpose of enhancement of its appearance, so that the machining work is complicated.

To solve the problem, the inventor of this invention has invented a lamp device for vehicle (Japanese Patent Application No. 11-209331 (Japanese Patent Application Laid-Open No. 2001-35215)) by which the interior is harder to be seen as compared to the permeable lens.

SUMMARY OF THE INVENTION

It is an object of this invention is to provide a lamp device for vehicle, by which a surface finish is more easily given to the reflecting surface of a reflector than the conventional way by making the interior harder to be seen as compared to the permeable lens.

It is another object of this invention to provide a lamp device for vehicle whose lens is easily polished when it is made of glass by forming the shape of the lens to be flat in vertical cross section or transverse cross section, which is excellent in manufacture of the lens.

In order to achieve the objects, this invention provides a lens having a concave shape or a convex shape in either one of vertical cross section and transverse cross section while having a flat shape in the other one of these sections.

As a result, this invention provides the lens that forms a concave shape or a convex shape in either one of vertical cross section and transverse cross section, and thereby the interior is harder to be seen because the light passing through the lens is largely refracted even if a prism is not provided. This invention does not therefore require giving a finish more than optical performance required for reflection to the front surface of the reflecting surface of the reflector, which is for the purpose of enhancement of its appearance, and thereby the machining work is simpler than the conventional way.

In this invention, the lens has a flat shape in the other one of vertical cross section and transverse cross section. Therefore, the lens, which is made of glass, can be easily polished and is therefore excellent in its manufacture.

DETAILED DESCRIPTIONS

Four embodiments of the lamp device for vehicle according to this invention will be explained below with reference to the attached drawings. It should be noted that this invention is not limited by these embodiments.

The first to fourth embodiments provide explanation about a vehicle headlamp with which a low-beam light distribution pattern (light distribution pattern used when vehicles pass each other) can be obtained. This invention is also applicable to some other lamp device for vehicles. For example, this invention is applicable to a vehicle headlamp with which a high-beam light distribution pattern, light distribution pattern for highway driving, and a light distribution pattern for city driving, or the like can be obtained, or applicable to a vehicle fog lamp with which a light distribution pattern used under heavy fog is obtained.

The respective vehicle headlamps according to the first to fourth embodiments are mounted on vehicles specific to left-side driving. Therefore, for the vehicle headlamp mounted on vehicles specific to right-side driving, the right-hand side and the left-hand side in the figures are to be seen the other way around.

The vehicle headlamp according to the first embodiment comprises the lens 1 A disposed on the front of a lamp housing (not shown), light source 2 , and the reflector 3 A. In the figures, the legend S represents an optical axis.

As shown in FIG. 1 to FIG. 4 , the lens 1 A has an outside shape of a laterally elongated rectangle when viewed from the front side, a concave shape in vertical cross section, and a flat shape in transverse cross section (a shape whose outer surface and inner surface are substantially parallel and wall thickness is substantially constant). The lens 1 A is not provided with a prism for light distribution. Non-Uniform Rational B-Spline Surface (NURBS) as a free curved surface for light distribution is formed on the front surface and the rear surface of the lens 1 A. The lens 1 A may be made of glass or resin, and it is made of glass in the first embodiment. When the lens 1 A uses such a glass-made lens, polishing is easy because it has a flat shape in transverse cross section, which is excellent in manufacture of the lens 1 A.

The light source 2 uses, for example, a halogen lamp with a single filament or double filament, incandescent lamp, or electric discharge lamp (so called H 1 , H 3 , H 4 , H 7 , H 11 , etc.)

The internal surface of the reflector 3 A is provided with a reflecting surface 4 A such as NURBS as a free curved surface for light distribution. The reflecting surface 4 A exhibits metallic high brightness by means of aluminum evaporation or silver color coating. The reflector 3 A may be integrally formed with a lamp housing or may be formed as a single unit. The details of the reflecting surface 4 A as NURBS are described in, for example, Mathematical Elements for Computer Graphics (Devid F. Rogers, J Alan Adams).

That is, the NURBS reflecting surface 4 A when the NURBS lens 1 A is used for its front surface and rear surface can be computed from a general equation of the following equation (1)

The NURBS reflecting surface 4 A computed from the above equation (1) is a substantially ellipsoidal surface (the surface analogous to an ellipsoid) invertical cross section, which is larger than the lens 1 A as shown in FIG. 1 , and is a substantially paraboloidal surface (the surface analogous to paraboloid) in transverse cross section, which is almost the same in size as the lens 1 A as shown in FIG. 2 .

A parametric function of the general equation in the equation (1) is shown in the following equation (2).

By substituting a specific numerical value, for example, any point on the ellipsoid or paraboloid in the parametric function of the following equation (2), a specific reflecting surface 4 A of the reflector 3 A in a use of the lens 1 A can be obtained. Equation 2 N j s ( u ) = { 1 ( if u j u < u j + 1 ) 0 ( otherwise ) N j s ( u ) = u - u j u j + s - 1 - u j N j , s - 1 ( u ) + u j + s - u u j + s - u j + 1 N j + 1 , s - 1 ( u ) M k , t ( v ) = { 1 ( if v k v < v k + 1 ) 0 ( otherwise ) M k , t ( v ) = v - v k v k + t - 1 - v k M k , t - 1 ( v ) + v k + t - v v k + t - v k + 1 M k + 1 , t - 1 ( v ) ( 2 )

An example of the specific reflecting surface 4 A obtained in the above manner is shown in FIG. 5 . The example of the reflecting surface 4 A is longitudinally divided into 10 blocks. Boundaries (seams) of the 10-divided reflecting surface blocks (or reflecting surface segments) 21 A, 22 A, 23 A, 24 A, 25 A, 26 A, 27 A, 28 A, 29 A, and 30 A ( 21 A to 30 A) are sometimes visible independently from each other as shown in FIG. 5 and are sometimes not because they seem continuous.

The reflecting surface 4 A shown in FIG. 5 is an example of the longitudinally divided reflecting surface blocks. Therefore, this invention may be any of laterally divided reflecting surface blocks, reflecting surface blocks obtained by being divided in a parabolic direction, or those obtained by being divided in any combined directions of the longitudinal direction, lateral direction, and parabolic direction, if necessary.

Since the reflecting surface 4 A is provided with complex combination of reflecting surfaces as NURBS, as the optical axis S, the reflecting surface 4 A does not have a single optical axis in the strict sense. However, there is only a slight amount of difference between plural optical axes and the surfaces therefore share substantially the identical optical axis. Based on this, in this specification and the figures, this substantially identical optical axis is referred to as pseudo optical axis (or simply optical axis) S. Likewise, as a focal point F (see FIG. 7C ) on the reflecting surface 4 A, it does not have a single focal point in the strict sense, but there is only a slight amount of difference between plural focal points, and the surfaces therefore share substantially the identical focal point. Based on this, in this specification and the figures, this substantially identical focal point is referred to as pseudo focal point (or simply focal point).

An example of manufacture of the reflecting surface 4 A will be explained below with reference to FIG. 6 .

At step 1 (S 1 ), data is entered to a microcomputer (not shown). This data is selected from, for example, design specifications of the database in consideration of design of vehicle headlamps and design of a vehicle with the vehicle headlamps mounted. This data includes a type of light source 2 , a size of the reflector 3 A and a surface shape of the reflecting surface 4 A, division to the reflecting surface blocks 21 A to 30 A, a size and shapes of top and rear surfaces of the lens 1 A, a target light distribution pattern, and the like.

At step 2 (S 2 ), the processing for temporarily setting a reflecting surface of a reflector is performed so as to obtain a target light distribution pattern in combination with a flat lens based on the data entered at step 1 . The reflecting surface of the temporarily set reflector is automatically set based on control points in a free curved surface as NURBS and a normal vector, or the like.

At step 3 (S 3 ), the processing for changing the flat lens to a flat-shaped lens 1 A is performed without changing of the reflecting surface of the temporarily set reflector obtained through the processing at step 2 , so that the lens 1 A has a concave shape in vertical cross section and a flat shape in transverse cross section. At this time, a light distribution pattern (not shown) of an image is obtained using through computation. More specifically, this image is created using a ray tracing method through some steps such that light from a modeled light source 2 is reflected on the reflecting surface of the reflector, the reflected light is refracted by the lens, and then the refracted light as emitted light reaches a screen frontward (not shown).

At step 4 (S 4 ), the following processing is performed. That is, displacement between the target light distribution pattern obtained through the processing at step 2 and the light distribution pattern obtained through the processing at step 3 is computed. This displacement is produced through light refraction in the lens 1 A.

At step 5 (S 5 ) and step 6 (S 6 ), the processing for finally setting the reflecting surface of the temporarily set reflector to the reflecting surface 4 A of the reflector 3 A for the lens 1 A is performed so that the displacement computed through the processing at step 4 is reduced to zero. That is, the NURBS free curved surface of the reflecting surface is automatically distorted for correction to form an optimal NURBS free curved surface so that the light distribution pattern obtained through the processing at step 3 is changed to the target light distribution pattern obtained through the processing at step 2 . In the respective processing at step 5 and step 6 , calculation for light ray tracing is repeated using the ray tracing method such that the light from the light source 2 is reflected by the reflecting surface 4 A of the reflector 3 A and the reflected light is refracted by the lens 1 A to reach the screen frontward (not shown) as emitted light.

At the point of time when the displacement is reduced to substantially zero, the reflecting surface 4 A of the reflector 3 A for the lens 1 A is finally set, and at step 7 (S 7 ), the finally set reflecting surface 4 A of the reflector 3 A is output.

As explained above, in this manufacturing method, the NURBS reflecting surface 4 A can be manufactured when the lens 1 A whose front surface and the rear surface are NURBS is used. Moreover, the processing at steps 2 to 6 , that is, the step of temporarily setting the reflecting surface 4 A of the reflector 3 A, step of computing displacement, and step of finally setting the reflecting surface 4 A of the reflector 3 A are performed according to a predetermined program by the computer, and thereby the reflecting surface 4 A can be manufactured with high accuracy at a high speed and with high flexibility.

The results of performing optical design simulation for the vehicle headlamp according to the first embodiment will be explained in detail below. FIG. 7A to FIG. 7D each show data to be entered to the optical design simulation. The respective data dimensions in FIG. 7A to FIG. 7D are as follows.

Ar 200 mm (lateral dimension of the reflector 3 A)

Br 90 mm (longitudinal dimension of the reflector 3 A)

Al 200 mm (lateral dimension of the lens 1 A)

Bl 50 mm (longitudinal dimension of the lens 1 A)

T 4 mm (wall thickness dimension (in the optical axis S) of the lens 1 A)

Sv 0 (inclined angle (in the optical axis S) of the side face of the lens 1 A)

Sh 0 (inclined angle (in the optical axis S) of the plane of the lens 1 A)

Rvo 100 mm (curvature radius of the side face in the front surface of the lens 1 A in the optical axis S)

Rho 800 mm (curvature radius of the plane in the front surface of the lens 1 A in optical axis S)

Rvi 200 mm (curvature radius of the side face in the rear surface of the lens 1 A in the optical axis S)

Rhi 740 mm (curvature radius of the plane in the rear surface of the lens 1 A in the optical axis S)

Lf 4.6 mm (length of the filament of the light source 2 )

Rf 0.73 mm (radius of the filament of the light source 2 )

The respective data is entered to the following table 1 as each value. Note that the conditions are assumed to satisfy the European Light Distribution Standard ECEReg.

TABLE 1 Reflector 3A Width Height Focal distance Ar (mm) Br (mm) F (mm) 200 90 24 The light source 2 of the vehicle headlamp according to the first embodiment is lit to obtain the result shown in the following table 2.

TABLE 2 European Light Distribution Satisfied Standard Maximum luminous intensity 27100 (cd) Using luminous intensity 474 (1m) Light-emitting Height 50 part of the lens Width 200 (mm) Wall 4 thickness The light source 2 of the vehicle headlamp according to the first embodiment is lit, and thereby light L 1 from the light source 2 is reflected by the reflecting surface 4 A of the reflector 3 A, as shown in FIG. 1 and FIG. 2 , and the reflected light beams L 2 and L 3 pass through the lens 1 A to be radiated as emitted light beams L 4 and L 5 to the outside as a target light distribution pattern as shown in FIG. 9 . This target light distribution pattern refers to light distribution patterns in conformity with the European Light Distribution Standard ECEReg. or an equivalent regulation (e.g., model recognition standard for vehicles sold in Japan), North America Light Distribution Standard, FMVSS, etc.

The target light distribution pattern shown in FIG. 9 is the low-beam light distribution pattern based on left-side driving, and is controlled by the respective reflecting surface blocks 21 A to 30 A of the reflecting surface 4 A of the reflector 3 A. That is, of the reflecting surface 4 A of the reflector 3 A shown in FIG. 5 , the reflecting surface block 21 A at the first from the left controls to obtain the light distribution pattern shown in FIG. 10 . The reflecting surface block 22 A at the second from the left controls to obtain the light distribution pattern shown in FIG. 11 . The reflecting surface block 23 A at the third from the left controls to obtain the light distribution pattern shown in FIG. 12 . The reflecting surface block 24 A at the fourth from the left controls to obtain the light distribution pattern shown in FIG. 13 . The reflecting surface block 25 A at the fifth from the left controls to obtain the light distribution pattern shown in FIG. 14 . The reflecting surface block 26 A at the sixth from the left controls to obtain the light distribution pattern shown in FIG. 15 . The reflecting surface block 27 A at the seventh from the left controls to obtain the light distribution pattern shown in FIG. 16 . The reflecting surface block 28 A at the eighth from the left controls to obtain the light distribution pattern shown in FIG. 17 . The reflecting surface block 29 A at the ninth from the left controls to obtain the light distribution pattern shown in FIG. 18 . The reflecting surface block 30 A in the tenth from the left controls to obtain the light distribution pattern shown in FIG. 19 . The light distribution patterns ( FIG. 10 to FIG. 19 ) obtained through control of these reflecting surface blocks 21 A to 30 A are combined, and thereby the target light distribution pattern shown in FIG. 9 can be obtained.

As clearly seen from FIG. 10 to FIG. 19 , since the reflecting blocks 21 A, 22 A, 29 A, and 30 A at the first, second, ninth, and tenth from the left are apart from the light source 2 , the reflected light beams are low. Therefore, low reflected light beams are collected to form a hot zone in these reflecting blocks 21 A, 22 A, 29 A, and 30 A. Accordingly, each of the reflecting surfaces of these reflecting blocks 21 A, 22 A, 29 A, and 30 A mainly forms a concave face.

On the other hand, since the reflecting blocks 23 A to 28 A in the third to eighth from the left are close to the light source 2 , the reflected light beams are high. Therefore, highly reflected light beams with which only a simple spot light is formed are dispersed. Accordingly, each of the reflecting surfaces of these reflecting blocks 23 A to 28 A mainly forms a convex face.

The reflecting surface 4 A is logically designed here assuming the light source 2 as a spot light source. The actual light source 2 , however, has a length and a width (radius) of the filament and is not therefore the spot light source but a surface light source as clearly seen in FIG. 1 and FIG. 2 .

Consequently, as shown in FIG. 5 , for example, when the light of the light source 2 is reflected at a point P 1 of the reflecting surface 4 A in the reflecting surface block 25 A at the fifth from the left which is the closest to the light source 2 , the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted downward by an angle 1 with respect to the horizontal line S 1 , as shown in FIG. 1 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted downward by an angle 2 with respect to the horizontal line S 1 . The emitted light beams L 4 and L 5 have longitudinally long lengths at a substantially central part on the screen as shown in FIG. 8 A and FIG. 14 . The angles 1 and 2 of the light beams L 4 and L 5 emitted from the lens 1 A with respect to the horizontal line S 1 are, as shown in FIG. 8A , the same as angles 1 and 2 from the horizontal line H H on the screen.

As shown in FIG. 5 , for example, when the light of the light source 2 is reflected at a point P 2 of the reflecting surface 4 A in the reflecting surface block 28 A at the eighth from the left, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted inward by an angle 4 with respect to the vertical line S 2 , as shown in FIG. 2 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted inward by an angle 3 with respect to the vertical line S 2 . The emitted light beams L 4 and L 5 have laterally long lengths close to the horizontal line H H on the right side of the screen as shown in FIG. 8 B and FIG. 17 , and is slightly inclined by the displacement in the lateral direction from the light source 2 . The angles 3 and 4 of the light beams L 4 and L 5 emitted from the lens 1 A with respect to the vertical line S 2 are, as shown in FIG. 8B , the same as angles 3 and 4 from the vertical line V V on the screen.

As explained above, the free curved surface formed on the reflecting surface 4 A is provided so that the light distribution patterns generated by the free curved surface are computer-simulated to analyze light distribution properties so as to form an optimal light distribution pattern. Therefore, when the light beams L 2 and L 3 reflected by the reflecting surface 4 A pass through the lens 1 A and are to be emitted to the outside, the light beams L 4 and L 5 emitted from the lens 1 A form the most appropriate light distribution pattern. Moreover, in the first embodiment, the free curved surface (NURBS) is formed on the front surface and rear surface of the lens 1 A, and thereby the light distribution function can be imparted not only to the reflecting surface 4 A but also to the lens 1 A, so that a more ideal light distribution pattern can be obtained.

Particularly, the vehicle headlamp according to the first embodiment has the lens 1 A with a concave shape in vertical cross section, and thereby even if the prism is not formed thereon, light is largely refracted by the lens 1 A and the interior is harder to be seen from the outside. Consequently, the vehicle headlamp of the first embodiment does not require giving a finish more than optical performance required for reflection to the front surface of the reflecting surface 4 A of the reflector 3 A, which is for the purpose of enhancement of its appearance, thus the machining work is easier than the conventional work.

Further, the vehicle headlamp according to the first embodiment has the lens 1 A with a flat shape in transverse cross section, and thereby the lens 1 A can be easily polished when the lens 1 A is made of glass, which is excellent in manufacture of the lens 1 A.

The lens 1 A according to the first embodiment has a concave shape in vertical cross section and a flat shape in transverse cross section. Therefore, in the vertical cross section of the lens 1 A, as shown in FIG. 1 , the light beams L 2 and L 3 converged by the substantially ellipsoidal surface of the reflecting surface 4 A are dispersed in the direction substantially along the optical axis S. While in the transverse cross section of the lens 1 A, as shown in FIG. 2 , the light beams L 2 and L 3 reflected by the substantially paraboloidal surface of the reflecting surface 4 A pass through the lens as they are in the direction substantially along the optical axis S, and are emitted to the outside as the target light distribution pattern. As a result, the first embodiment provides the vehicle headlamp using the lens 1 A with a laterally elongated shape when viewed from the front side as shown in FIG. 3 . Accordingly, the first embodiment is right fit for car body design in a case where the front section cannot afford to keep sufficient room for installation of the vehicle headlamps in longitudinal dimensions.

Further, the reflecting surface 4 A of the first embodiment is a substantially ellipsoidal surface in vertical cross section, which is larger than the lens 1 A, and is a substantially paraboloidal surface in transverse cross section, which is almost the same size as that of the lens 1 A. Therefore, in the vertical cross section of the reflecting surface 4 A, as shown in FIG. 1 , the light beams L 2 and L 3 can be led to the lens 1 A while being kept vertically converged substantially along the optical axis S. Further, in the transverse cross section of the reflecting surface 4 A, as shown in FIG. 2 , the light beams L 2 and L 3 can be led to the lens 1 A while being kept substantially along the optical axis S. As a result, the first embodiment is the most suitable for a combination with the lens 1 A having a concave shape in vertical cross section and a flat shape in transverse cross section. As shown in FIG. 3 , the vehicle headlamp whose front surface (the surface of the lens 1 A) is longitudinally short and laterally long can easily be obtained. Furthermore, light is converged in a broad range by the substantially ellipsoidal surface that is larger than the lens 1 A to be reflected to the side of the lens 1 A in the vertical direction of the reflecting surface 4 A, and therefore there is no problem in terms of an optical amount.

In the first embodiment, the concave shape of the lens 1 A in vertical cross section here indicates a shape having an optical function that refracts an incident light in a direction in which the light is separated (dispersed) from the optical axis S in the vertical cross section of the lens 1 A. Therefore, the concave shape includes a shape having a concave shape only in one side as shown in FIG. 20A , a shape having a convex shape in one side and a concave shape in the other side whose degree of curve is greater than that of the convex shape as shown in FIG. 20B , and a shape inclined with respect to the optical axis S as shown in FIG. 20 C.

FIG. 21 to FIG. 34 show a second embodiment. In the figures, the same legends as these in FIG. 1 to FIG. 20 represent the same sections.

The vehicle headlamp according to the second embodiment comprises the lens 1 B, light source 2 , and the reflector 3 B.

The lens 1 B, as shown in FIG. 21 to FIG. 24 , has an outside shape of a longitudinally elongated rectangle when viewed from the front side, a flat shape in vertical cross section, and a concave shape in transverse cross section. The lens 1 B is formed like the lens 1 A of the first embodiment. That is, the lens 1 B is not provided with a prism for light distribution. NURBS as a free curved surface for light distribution is formed on the front surface and the rear surface of the lens 1 B.

The internal surface of the reflector 3 B is provided with a reflecting surface 4 B such as NURBS as a free curved surface for light distribution. The reflecting surface 4 B is formed corresponding to the lens 1 B like the reflecting surface 4 A of the first embodiment. As shown in FIG. 21 , this reflecting surface 4 B is a substantially paraboloidal surface in vertical cross section, which is almost the same size as the lens 1 B, and is a substantially ellipsoidal surface in transverse cross section, which is larger than the lens 1 B. As an example of this reflecting surface 4 B, the surface is laterally divided into six blocks as shown in FIG. 25 .

Boundaries of the 6-divided reflecting surface blocks 21 B, 22 B, 23 B, 24 B, 25 B, and 26 B are sometimes visible independently from each other and sometimes not.

The reflecting blocks of the reflecting surface 4 B may include those obtained through division of the surface in the longitudinal direction, other than the lateral direction, in the parabolic direction, and in any directions as a combination of the longitudinal direction, lateral direction, and parabolic direction, if necessary. That is, the reflecting surface is divided into blocks in terms of design.

The manufacturing method of the reflecting surface 4 B is performed in the same manner as that of the reflecting surface 4 A of the first embodiment.

The results of performing optical design simulation for the vehicle headlamp according to the second embodiment will be explained in detail below. FIG. 26A to FIG. 26D each show data to be entered to the optical design simulation. The respective data dimensions in FIG. 26A to FIG. 26D are as follows.

Ar 60 mm (lateral dimension of the reflector 3 B)

Br 120 mm (longitudinal dimension of the reflector 3 B)

Al 100 mm (lateral dimension of the lens 1 B)

Bl 120 mm (longitudinal dimension of the lens 1 B)

T 4 mm (wall thickness dimension (in the optical axis S) of the lens 1 B)

Sv 0 (inclined angle (in the optical axis S) of the side face of the lens 1 B)

Sh 0 (inclined angle (in the optical axis S) of the plane of the lens 1 B)

Rvo 1400 mm (curvature radius of the side face in the front surface of the lens 1 B in the optical axis S)

Rho 1400 mm (curvature radius of the plane in the front surface of the lens 1 B in the optical axis S)

Rvi 1400 mm (curvature radius of the side face in the rear surface of the lens 1 B in the optical axis S)

Rhi 200 mm (curvature radius of the plane in the rear surface of the lens 1 B in the optical axis S)

Lf 4.6 mm (length of the filament of the light source 2 )

Rf 0.73 mm (radius of the filament of the light source 2 )

The respective data is entered to the following table 3 as each value. Note that the conditions are assumed to satisfy the European Light Distribution Standard ECEReg.

TABLE 3 Reflector 3B Width Height Focal distance Ar (mm) Br (mm) F (mm) 60 120 22 The light source 2 of the vehicle headlamp according to the second embodiment is lit to obtain the result shown in the following table 4.

TABLE 4 European Light Distribution Satisfied Standard Maximum luminous intensity 18530 (cd) Using luminous intensity 375 (1m) Light-emitting Height 120 part of the lens Width 100 (mm) Wall 4 thickness The light source 2 of the vehicle headlamp according to the second embodiment is lit and thereby a target light distribution pattern as shown in FIG. 28 is obtained.

The target light distribution pattern shown in FIG. 28 is the low-beam light distribution pattern based on left-side driving, and is controlled by the respective reflecting surface blocks 21 B to 26 B of the reflecting surface 4 B of the reflector 3 B. That is, of the reflecting surface 4 B of the reflector 3 B shown in FIG. 25 , the reflecting surface block 21 B at the first from the top controls to obtain the light distribution pattern shown in FIG. 29 . The reflecting surface block 22 B at the second from the top controls to obtain the light distribution pattern shown in FIG. 30 . The reflecting surface block 23 B at the third from the top controls to obtain the light distribution pattern shown in FIG. 31 . The reflecting surface block 24 B at the fourth from the top controls to obtain the light distribution pattern shown in FIG. 32 . The reflecting surface block 25 B at the fifth from the top controls to obtain the light distribution pattern shown in FIG. 33 . The reflecting surface block 26 B at the sixth from the top controls to obtain the light distribution pattern shown in FIG. 34 . The light distribution patterns ( FIG. 29 to FIG. 34 ) obtained through control of these reflecting surface blocks 21 B to 26 B are combined, and thereby the target light distribution pattern shown in FIG. 28 can be obtained.

As clearly seen from FIG. 29 to FIG. 34 , the reflecting blocks 21 B, 22 B, 23 B, and 26 B at the first, second, third, and sixth from the top disperse reflected light beams. Therefore, each of respective reflecting surfaces of these reflecting blocks 21 B, 22 B, 23 B, and 26 B mainly forms a convex face. While the reflecting blocks 24 B and 25 B at the forth and fifth from the top converge the reflected light beams to form a hot zone. Therefore, each of the reflecting surfaces of these reflecting blocks 24 B and 25 B mainly forms a concave face.

The reflecting surface 4 B is logically designed here assuming the light source 2 as a spot light source. The actual light source 2 , however, has a length and a width (radius) of the filament and is not therefore the spot light source but a surface light source as clearly seen in FIG. 21 and FIG. 22 .

Therefore, as shown in FIG. 25 , for example, when the light of the light source 2 is reflected at a point P 1 in the reflecting surface block 21 B at the first from the top, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted downward by an angle 1 with respect to the horizontal line S 1 , as shown in FIG. 21 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted downward by an angle 2 with respect to the horizontal line S 1 . The emitted light beams L 4 and L 5 have longitudinally long lengths at a substantially central part on the screen as shown in FIG. 27 A and FIG. 29 . The angles 1 and 2 of the light beams L 4 and L 5 emitted from the lens 1 B with respect to the horizontal line S 1 are, as shown in FIG. 27A , the same as angles 1 and 2 from the horizontal line H H on the screen.

As shown in FIG. 25 , for example, when the light of the light source 2 is reflected at a point P 2 in the reflecting surface block 24 B at the fourth from the top, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted inward by an angle 4 with respect to the vertical line S 2 , as shown in FIG. 22 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted inward by an angle 3 with respect to the vertical line S 2 . The emitted light beams L 4 and L 5 have laterally long lengths close to the left hand side of the substantially central part of the screen as shown in FIG. 27 B and FIG. 32 , and is slightly inclined by the displacement in the lateral direction from the light source 2 . The angles 3 and 4 of the light beams L 4 and L 5 emitted from the lens 1 B with respect to the vertical line S 2 are, as shown in FIG. 27B , the same as angles 3 and 4 from the vertical line V V on the screen.

As explained above, the free curved surface formed on the reflecting surface 4 B is provided so that the light distribution patterns generated by the free curved surface are computer-simulated to analyze light distribution properties so as to form an optimal light distribution pattern. Therefore, when the light beams L 2 and L 3 reflected by the reflecting surface 4 B pass through the lens 1 B and are to be emitted to the outside, the light beams L 4 and L 5 emitted from the lens 1 B form the most appropriate light distribution pattern. Moreover, in the second embodiment, the free curved surface (NURBS) is formed on the front surface and rear surface of the lens 1 B, and thereby the light distribution function can be imparted not only to the reflecting surface 4 B but also to the lens 1 B, so that a more ideal light distribution pattern can be obtained.

Particularly, the vehicle headlamp according to the second embodiment has the lens 1 B with a concave shape in transverse cross section, and thereby even if the prism is not formed thereon, light is largely refracted by the lens 1 B and the interior is harder to be seen from the outside. Consequently, the vehicle headlamp of the second embodiment does not require giving a finish more than optical performance required for reflection to the front surface of the reflecting surface 4 B of the reflector 3 B, which is for the purpose of enhancement of its appearance, thus the machining work is easier than the conventional work.

Further, the vehicle headlamp according to the second embodiment has the lens 1 B with a flat shape in vertical cross section, and therefore the lens 1 B can be easily polished when it is made of glass, which is excellent in manufacture of the lens 1 B.

The lens 1 B of the first embodiment has a flat shape in vertical cross section and a concave shape in transverse cross section. Therefore, in the vertical cross section of the lens 1 B, as shown in FIG. 21 , the light beams L 2 and L 3 reflected by the substantially paraboloidal surface of the reflecting surface 4 B pass through the lens 1 B as they are in the direction substantially along the optical axis S. While in the transverse cross section of the lens 1 B, as shown in FIG. 22 , the light beams L 2 and L 3 converged by the substantially ellipsoidal surface of the reflecting surface 4 B are dispersed in the direction substantially along the optical axis S and emitted to the outside as the target light distribution pattern. As a result, the second embodiment provides the vehicle headlamp using the lens 1 B with a longitudinally elongated shape when viewed from the front side as shown in FIG. 23 . Therefore, the second embodiment is right fit for car body design in a case where the front section cannot afford to keep sufficient room for installation of the vehicle headlamp in lateral dimensions.

Further, the reflecting surface 4 B of the second embodiment is a substantially paraboloidal surface in vertical cross section, which is almost the same size as the lens 1 B, and is a substantially ellipsoidal surface in transverse cross section, which is larger than the lens 1 B. Therefore, in the vertical cross section of the reflecting surface 4 B, as shown in FIG. 21 , the light beams L 2 and L 3 can be led to the lens 1 B while being kept substantially along the optical axis S. Further, in the transverse cross section of the reflecting surface 4 B, as shown in FIG. 22 , the light beams L 2 and L 3 can be led to the lens 1 B while being kept laterally converged substantially along the optical axis S. As a result, the second embodiment is the most suitable for a combination with the lens 1 B having a flat shape in vertical cross section and a concave shape in transverse cross section. As shown in FIG. 23 , the vehicle headlamp whose front surface (the surface of the lens 1 B) is longitudinally long and laterally short can easily be obtained. Furthermore, light is converged in a broad range by the substantially ellipsoidal surface that is larger than the lens 1 B to be reflected to the side of the lens 1 B in the lateral direction of the reflecting surface 4 B and therefore there is no problem in terms of an optical amount.

In the second embodiment, the concave shape of the lens 1 A in transverse cross section here indicates a shape having an optical function that refracts an incident light in a direction in which the light is separated (dispersed) from the optical axis S in the transverse cross section of the lens 1 B. Therefore, the concave shape includes a shape having a concave shape only in one side as shown in FIG. 20A , a shape having a convex shape in one side and a concave shape in the other side whose degree of curve is greater than that of the convex shape as shown in FIG. 20B , and a shape inclined with respect to the optical axis S as shown in FIG. 20 C.

FIG. 35 to FIG. 49 show a third embodiment. In the figures, the same legends as these in FIG. 1 to FIG. 34 represent the same sections.

The vehicle headlamp according to the third embodiment comprises the lens 1 C, light source 2 , and the reflector 3 .

The lens 1 C, as shown in FIG. 35 to FIG. 38 , has an outside shape of a longitudinally elongated rectangle when viewed from the front side, a convex shape in vertical cross section, and a flat shape in transverse cross section. The lens 1 C is formed like the lenses 1 A and 1 B of the first and second embodiments. That is, the lens 1 C is not provided with a prism for light distribution. NURBS as a free curved surface for light distribution is formed on the front surface and the rear surface of the lens 1 C.

The internal surface of the reflector 3 C is provided with a reflecting surface 4 C such as NURBS as a free curved surface for light distribution. The reflecting surface 4 C is formed corresponding to the lens 1 C like the reflecting surfaces 4 A and 4 B of the first and second embodiments. As shown in FIG. 35 , this reflecting surface 4 C is a substantially hyperboloidal surface (the surface analogous to the hyperboloid) in vertical cross section, which is smaller than the lens 1 C, and is a substantially paraboloidal surface in transverse cross section, which is almost the same size as the lens 1 C as shown in FIG. 36 . As an example of this reflecting surface 4 C, the surface is longitudinally divided into six blocks as shown in FIG. 39 .

Boundaries of the 6-divided reflecting surface blocks 21 C, 22 C, 23 C, 24 C, 25 C, and 26 C are sometimes visible independently from each other and sometimes not.

The reflecting blocks of the reflecting surface 4 C may include those obtained through division of the surface in the lateral direction, other than the longitudinal direction, in the parabolic direction, and in any directions as a combination of the longitudinal direction, lateral direction, and parabolic direction, if necessary. That is, the reflecting surface is divided into blocks in terms of design.

The manufacturing method of the reflecting surface 4 C is performed in the same manner as that of the reflecting surfaces 4 A and 4 B of the first and second embodiments.

The results of performing optical design simulation for the vehicle headlamp according to the third embodiment will be explained in detail below. FIG. 40A to FIG. 40D each show data to be entered to the optical design simulation. The respective data dimensions in FIG. 40A to FIG. 40D are as follows.

Ar 120 mm (lateral dimension of the reflector 3 C)

Br 80 mm (longitudinal dimension of the reflector 3 C)

Al 120 mm (lateral dimension of the lens 1 C)

Bl 120 mm (longitudinal dimension of the lens 1 C)

T 20 mm (wall thickness dimension (in the optical axis S) of the lens 1 C)

Sv 0 (inclined angle (in the optical axis S) of the side face of the lens 1 C)

Sh 0 (inclined angle (in the optical axis S) of the plane of the lens 1 C)

Rvo 1400 mm (curvature radius of the side face in the front surface of the lens 1 C in the optical axis S)

Rho 1400 mm (curvature radius of the plane in the front surface of the lens 1 C in the optical axis S)

Rvi 130 mm (curvature radius of the side face in the rear surface of the lens 1 C in the optical axis S)

Rhi 1400 mm (curvature radius of the plane in the rear surface of the lens 1 C in the optical axis S)

Lf 4.6 mm (length of the filament of the light source 2 )

Rf 0.73 mm (radius of the filament of the light source 2 )

The respective data is entered to the following table 5 as each value. Note that the conditions are assumed to satisfy the European Light Distribution Standard ECEReg.

TABLE 5 Reflector 3C Width Height Focal distance Ar (mm) Br (mm) F (mm) 120 80 22 The light source 2 of the vehicle headlamp according to the third embodiment is lit to obtain the result shown in the following table 6.

TABLE 6 European Light Distribution Satisfied Standard Maximum luminous intensity 22830 (cd) Using luminous intensity 404 (1m) Light-emitting Height 120 part of the lens Width 120 (mm) Wall 20 thickness The light source 2 of the vehicle headlamp according to the third embodiment is lit and thereby a target light distribution pattern as shown in FIG. 42 is obtained.

The target light distribution pattern shown in FIG. 42 is the low-beam light distribution pattern based on left-side driving, and is controlled by the respective reflecting surface blocks 21 C to 26 C of the reflecting surface 4 C of the reflector 3 C. That is, of the reflecting surface 4 C of the reflector 3 C shown in FIG. 39 , the reflecting surface block 21 C at the first from the left controls to obtain the light distribution pattern shown in FIG. 43 . The reflecting surface block 22 C at the second from the left controls to obtain the light distribution pattern shown in FIG. 44 . The reflecting surface block 23 C at the third from the left controls to obtain the light distribution pattern shown in FIG. 45 . The reflecting surface block 24 C at the fourth from the left controls to obtain the light distribution pattern shown in FIG. 46 . The reflecting surface block 25 C at the fifth from the left controls to obtain the light distribution pattern shown in FIG. 47 . The reflecting surface block 26 C at the sixth from the left controls to obtain the light distribution pattern shown in FIG. 48 . The light distribution patterns ( FIG. 43 to FIG. 48 ) obtained through control of these reflecting surface blocks 21 C to 26 C are combined, and thereby the target light distribution pattern shown in FIG. 42 can be obtained.

As clearly seen from FIG. 43 to FIG. 48 , since the reflecting blocks 21 C, 22 C, and 26 C at the first, second, and sixth from the top are apart from the light source 2 , the reflected light beams are low. Therefore, low reflected light beams are collected to form a hot zone in these reflecting blocks 21 C, 22 C, and 26 C. Accordingly, each of the reflecting surfaces of these reflecting blocks 21 C, 22 C, and 26 C mainly forms a concave face.

On the other hand, since the reflecting blocks 23 C to 25 C in the third to fifth from the left are close to the light source 2 , the reflected light beams are high and therefore highly reflected light beams with which only a simple spot light is formed are dispersed. Accordingly, each of the reflecting surfaces of these reflecting blocks 23 C to 25 C mainly forms a convex face.

The reflecting surface 4 C is logically designed here assuming the light source 2 as a spot light source. The actual light source 2 , however, has a length and a width (radius) of the filament and is not therefore the spot light source but a surface light source as clearly seen in FIG. 35 and FIG. 36 .

Therefore, as shown in FIG. 39 , for example, when the light of the light source 2 is reflected at a point P 1 of the reflecting surface 23 C at the third from the left, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted downward by an angle 1 with respect to the horizontal line S 1 , as shown in FIG. 35 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted downward by an angle 2 with respect to the horizontal line S 1 . The emitted light beams L 4 and L 5 have longitudinally long lengths at a substantially central part on the screen as shown in FIG. 41 B and FIG. 45 , and are slightly inclined by a displacement in the lateral direction from the light source 2 . The angles 1 and 2 of the light beams L 4 and L 5 emitted from the lens 1 C with respect to the horizontal line S 1 , are, as shown in FIG. 41B , the same as angles 1 and 2 from the horizontal line H H on the screen.

As shown in FIG. 39 , for example, when the light of the light source 2 is reflected at a point P 2 in the reflecting surface block 21 C at the first from the left, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted inward by an angle 4 with respect to the vertical line S 2 , as shown in FIG. 36 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted inward by an angle 3 with respect to the vertical line S 2 . The emitted light beams L 4 and L 5 have laterally long lengths at the central part yet slightly left on the screen as shown in FIG. 41 A and FIG. 43 . The angles 3 and 4 of the light beams L 4 and L 5 emitted from the lens 1 C with respect to the vertical line S 2 are, as shown in FIG. 41A , the same as angles 3 and 4 from the vertical line V V on the screen.

As explained above, the free curved surface formed on the reflecting surface 4 C is provided so that the light distribution patterns generated by the free curved surface are computer-simulated to analyze light distribution properties so as to form an optimal light distribution pattern. Therefore, when the light beams L 2 and L 3 reflected by the reflecting surface 4 C pass through the lens 1 C and are to be emitted to the outside, the light beams L 4 and L 5 emitted from the lens 1 C form the most appropriate light distribution pattern. Moreover, in the third embodiment, the free curved surface (NURBS) is formed also on the front surface and rear surface of the lens 1 C, and thereby the light distribution function can be imparted not only to the reflecting surface 4 C but also to the lens 1 C, so that a more ideal light distribution pattern can be obtained.

Particularly, the vehicle headlamp according to the third embodiment has the lens 1 C with a convex shape in vertical cross section, and thereby even if the prism is not formed thereon, light is largely refracted by the lens 1 C and the interior is harder to be seen from the outside. Consequently, the vehicle headlamp according to the third embodiment does not require giving a finish more than optical performance required for reflection to the front surface of the reflecting surface 4 C of the reflector 3 C, which is for the purpose of enhancement of its appearance, thus the machining work is easier than the conventional work.

Further, the vehicle headlamp according to the third embodiment has the lens 1 C with a flat shape in transverse cross section, and therefore the lens 1 C can be easily polished when it is made of glass, which is excellent in manufacture of the lens 1 C.

The lens 1 C of the third embodiment has a convex shape in vertical cross section and a flat shape in transverse cross section. Therefore, in vertical cross section of the lens 1 C, as shown in FIG. 35 , the light beams L 2 and L 3 dispersed by the substantially hyperboloidal surface of the reflecting surface 4 C are converged in the direction substantially along the optical axis S. While in the transverse cross section of the lens 1 C, as shown in FIG. 36 , the light beams L 2 and L 3 reflected by the substantially paraboloidal surface of the reflecting surface 4 C pass through the lens 1 C as they are in the direction substantially along the optical axis S, and are emitted to the outside as the target light distribution pattern. As a result, the third embodiment provides the vehicle headlamp using the lens 1 C with a longitudinally elongated shape when viewed from the front side as shown in FIG. 37 . Therefore, the third embodiment is right fit for car body design in a case where the front section cannot afford to keep sufficient room for installation of the vehicle headlamp in lateral dimensions.

Further, the reflecting surface 4 C in the third embodiment is a substantially hyperboloidal surface in vertical cross section, which is smaller than the lens 1 C, and is a substantially paraboloidal surface in transverse cross section, which is almost the same size as that of the lens 1 C. Therefore, in the vertical cross section of the reflecting surface 4 C, as shown in FIG. 35 , the light beams L 2 and L 3 can be led to the lens 1 C while being kept vertically dispersed with respect to the optical axis S. Further, in the transverse cross section of the reflecting surface 4 C, as shown in FIG. 36 , the light beams L 2 and L 3 can be led to the lens 1 C while being kept substantially along the optical axis S. As a result, the third embodiment is the most suitable for a combination with the lens 1 C having a convex shape in vertical cross section and a flat shape in transverse cross section. As shown in FIG. 37 , the vehicle headlamp whose front surface (the surface of the lens 1 C) is longitudinally long and laterally short can easily be obtained. Furthermore, in the vertical direction of the reflecting surface 4 C, the longitudinal dimension of the reflector 3 C can be minimized by the substantially hyperboloidal surface that is smaller than the lens 1 C.

In the third embodiment, the convex shape of the lens 1 C in vertical cross section here indicates a shape having an optical function that refracts an incident light in a direction in which the light is converged from the optical axis S in the vertical cross section of the lens 1 C. Therefore, the convex shape includes a shape having a convex shape only in one side as shown in FIG. 49A , a shape having a concave shape in one side and a convex shape in the other side whose degree of curve is greater than that of the concave shape as shown in FIG. 49B , and a shape inclined with respect to the optical axis S as shown in FIG. 49 C.

FIG. 50 to FIG. 64 show a fourth embodiment. In the figures, the same legends as these in FIG. 1 to FIG. 49 represent the same sections.

The vehicle headlamp according to the fourth embodiment comprises the lens 1 D, light source 2 , and the reflector 3 D.

The lens 1 D, as shown in FIG. 50 to FIG. 53 , has an outside shape of a laterally elongated rectangle when viewed from the front side, a flat shape in vertical cross section, and a convex shape in transverse cross section. The lens 1 D is formed like the lenses 1 A, 1 B, and 1 C of the first, second, and third embodiments. That is, the lens 1 D is not provided with a prism for light distribution. NURBS as a free curved surface for light distribution is formed on the front surface and the rear surface of the lens 1 D.

The internal surface of the reflector 3 D is provided with a reflecting surface 4 D such as NURBS as a free curved surface for light distribution. The reflecting surface 4 D is formed corresponding to the lens 1 D like the reflecting surfaces 4 A, 4 B, and 4 C of the first, second, and third embodiments. As shown in FIG. 50 , this reflecting surface 4 D is a substantially paraboloidal surface in vertical cross section, which is almost the same size as the lens 1 D, and is a substantially hyperboloidal surface in transverse cross section, which is smaller than the lens 1 D as shown in FIG. 51 . As an example of this reflecting surface 4 D, the surface is longitudinally divided into five blocks, two of which are also laterally divided into two, respectively, so that the surface eventually has seven blocks in total, as shown in FIG. 54 .

Boundaries of the 7-divided reflecting surface blocks 21 D, 22 D, 23 D, 24 D, 25 D, 26 C, and 27 D are sometimes visible independently from each other and sometimes not.

The reflecting blocks of the reflecting surface 4 D may include those obtained through division of the surface in the longitudinal direction, in the lateral direction, in the parabolic direction, and in any directions as a combination of the longitudinal direction, lateral direction, and parabolic direction, if necessary. That is, the reflecting surface is divided into blocks in terms of design.

The manufacturing method of the reflecting surface 4 D is performed in the same manner as that of the reflecting surfaces 4 A, 4 B, and 4 C of the first, second, and third embodiments.

The results of performing optical design simulation for the vehicle headlamp according to the fourth embodiment will be explained in detail below. FIG. 55A to FIG. 55D each show data to be entered to the optical design simulation. The respective data dimensions in FIG. 55A to FIG. 55D are as follows.

Ar 100 mm (lateral dimension of the reflector 3 D)

Br 100 mm (longitudinal dimension of the reflector 3 D)

Al 120 mm (lateral dimension of the lens 1 D)

Bl 100 mm (longitudinal dimension of the lens 1 D)

T 28 mm (wall thickness dimension (in the optical axis S) of the lens 1 D)

Sv 0 (inclined angle (in the optical axis S) of the side face of the lens 1 D)

Sh 0 (inclined angle (in the optical axis S) of the plane of the lens 1 D)

Rvo 1400 mm (curvature radius of the side face in the front surface of the lens 1 D in the optical axis S)

Rho 300 mm (curvature radius of the plane in the front surface of the lens 1 D in the optical axis S)

Rvi 1400 mm (curvature radius of the side face in the rear surface of the lens 1 D in the optical axis S)

Rhi 200 mm (curvature radius of the plane in the rear surface of the lens 1 D in the optical axis S)

Lf 4.6 mm (length of the filament of the light source 2 )

Rf 0.73 mm (radius of the filament of the light source 2 )

The respective data is entered to the following table 7 as each value. Note that the conditions are assumed to satisfy the European Light Distribution Standard ECEReg.

TABLE 7 Reflector 3D Width Height Focal distance Ar (mm) Br (mm) F (mm) 100 100 18 The light source 2 of the vehicle headlamp according to the fourth embodiment is lit to obtain the result shown in the following table 8.

TABLE 8 European Light Distribution Satisfied Standard Maximum luminous intensity 18000 (cd) Using luminous intensity 412 (1m) Light-emitting Height 100 part of the lens Width 120 (mm) Wall 28 thickness The light source 2 of the vehicle headlamp according to the fourth embodiment is lit and thereby a target light distribution pattern as shown in FIG. 57 is obtained.

The target light distribution pattern shown in FIG. 57 is the low-beam light distribution pattern based on left-side driving, and is controlled by the respective reflecting surface blocks 21 D to 27 D of the reflecting surface 4 D of the reflector 3 D. That is, of the reflecting surface 4 D of the reflector 3 D shown in FIG. 54 , the reflecting surface block 21 D at the first from the left controls to obtain the light distribution pattern shown in FIG. 58 . The upper reflecting surface block 22 D at the second from the left controls to obtain the light distribution pattern shown in FIG. 59 . The lower reflecting surface block 23 D at the second from the left controls to obtain the light distribution pattern shown in FIG. 60 . The upper reflecting surface block 24 D at the third from the left controls to obtain the light distribution pattern shown in FIG. 61 . The lower reflecting surface block 25 D at the third from the left controls to obtain the light distribution pattern shown in FIG. 62 . The reflecting surface block 26 D at the fourth from the left controls to obtain the light distribution pattern shown in FIG. 63 . The reflecting surface block 27 D at the fifth from the left controls to obtain the light distribution pattern shown in FIG. 64 . The light distribution patterns ( FIG. 58 to FIG. 64 ) obtained through control of these reflecting surface blocks 21 D to 27 D are combined, and thereby the target light distribution pattern shown in FIG. 57 can be obtained. Note that the upper and lower used in the explanation of the reflecting blocks 21 D to 27 D indicate the positions with respect to the light source 2 .

As clearly seen from FIG. 58 to FIG. 64 , in the reflecting blocks 21 D and 27 D at the first and fifth from the left, the light source 2 (filament) is projected in a substantially lateral position. In the reflecting blocks 22 D, 23 D, and 26 D at the upper and lower sides of the second from the left and at the fourth from the left, the light source 2 (filament) is projected in an inclined position. In the reflecting blocks 24 D and 25 D at the upper and lower sides of the third from the left, the light source 2 (filament) is projected in a substantially longitudinal position.

The reflecting surface 4 D is logically designed here assuming the light source 2 as a spot light source. The actual light source 2 , however, has a length and a width (radius) of the filament and is not therefore the spot light source but a surface light source as clearly seen in FIG. 50 and FIG. 51 .

Therefore, as shown in FIG. 54 , for example, when the light of the light source 2 is reflected at a point P 1 of the upper reflecting surface 24 D at the third from the left, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted downward by an angle 1 with respect to the horizontal line S 1 , as shown in FIG. 50 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted downward by an angle 2 with respect to the horizontal line S 1 . The emitted light beams L 4 and L 5 have vertically long lengths at a substantially central part on the screen as shown in FIG. 56 B and FIG. 61 . The angles 1 and 2 of the light beams L 4 and L 5 emitted from the lens 1 D with respect to the horizontal line S 1 are, as shown in FIG. 56B , the same as angles 1 and 2 from the horizontal line H H on the screen.

As shown in FIG. 54 , for example, when the light of the light source 2 is reflected at a point P 2 in the reflecting surface block 21 D at the first from the left, the light beam L 5 emitted from the rear end b of the light source (filament) 2 is emitted inward by an angle 4 with respect to the vertical line S 2 , as shown in FIG. 51 . On the other hand, the light beam L 4 emitted from the front end a of the light source (filament) 2 is emitted inward by an angle 3 with respect to the vertical line S 2 . The emitted light beams L 4 and L 5 have laterally long lengths on the horizontal line H H at the left hand side of the screen as shown in FIG. 56 A and FIG. 58 . The angles 3 and 4 of the light beams L 4 and L 5 emitted from the lens 1 D with respect to the vertical line S 2 are, as shown in FIG. 56A , the same as angles 3 and 4 from the vertical line V V on the screen.

As explained above, the free curved surface formed on the reflecting surface 4 D is provided so that the light distribution patterns generated by the free curved surface are computer-simulated to analyze light distribution properties so as to form an optimal light distribution pattern. Therefore, when the light beams L 2 and L 3 reflected by the reflecting surface 4 D pass through the lens 1 D and are to be emitted to the outside, the light beams L 4 and L 5 emitted from the lens 1 D form the most appropriate light distribution pattern. Moreover, in the fourth embodiment, the free curved surface (NURBS) is formed also on the front surface and rear surface of the lens 1 D, and thereby the light distribution function can be imparted not only to the reflecting surface 4 D but also to the lens 1 D, so that a more ideal light distribution pattern can be obtained.

Particularly, the vehicle headlamp according to the fourth embodiment has the lens 1 D with a convex shape in transverse cross section, and thereby even if the prism is not formed thereon, light is largely refracted by the lens 1 D and the interior is harder to be seen from the outside. Consequently, the vehicle headlamp according to the fourth embodiment does not require giving a finish more than optical performance required for reflection to the front surface of the reflecting surface 4 D of the reflector 3 D, which is for the purpose of enhancement of its appearance, thus the machining work is easier than the conventional work.

Further, the vehicle headlamp according to the fourth embodiment has the lens 1 D with a flat shape in vertical cross section, and therefore the lens 1 D can be easily polished when it is made of glass, which is excellent in manufacture of the lens 1 D.

The lens 1 D of the fourth embodiment has a flat shape in vertical cross section and a convex shape in transverse cross section. Therefore, in the vertical cross section of the lens 1 D, as shown in FIG. 50 , the light beams L 2 and L 3 reflected by the substantially paraboloidal surface of the reflecting surface 4 D pass through the lens 1 D as they are in the direction substantially along the optical axis S. While in the transverse cross section of the lens 1 D, as shown in FIG. 51 , the light beams L 2 and L 3 dispersed by the substantially hyperboloidal surface of the reflecting surface 4 D are converged in the direction substantially along the optical axis S, and are emitted to the outside as the target light distribution pattern. As a result, the fourth embodiment provides the vehicle headlamp using the lens 1 D with a longitudinally elongated shape when viewed from the front side as shown in FIG. 52 . Therefore, the fourth embodiment is right fit for car body design in a case where the front section cannot afford to keep sufficient room for installation of the vehicle headlamp in longitudinal dimensions.

Further, the reflecting surface 4 D of the fourth embodiment is a substantially paraboloidal surface in vertical cross section, which is almost the same size as that of the lens 1 D, and is a substantially hyperboloidal surface in transverse cross section, which is smaller than the lens 1 D. Therefore, in the vertical cross section of the reflecting surface 4 D, as shown in FIG. 50 , the light beams L 2 and L 3 can be led to the lens 1 D while being kept substantially along the optical axis S. Further, in the transverse cross section of the reflecting surface 4 D, as shown in FIG. 51 , the light beams L 2 and L 3 can be led to the lens 1 D while being kept laterally dispersed with respect to the optical axis S. As a result, the fourth embodiment is the most suitable for a combination with the lens 1 D having a flat shape in vertical cross section and a convex shape in transverse cross section. As shown in FIG. 52 , the vehicle headlamp whose front surface (the surface of the lens 1 D) is laterally long and longitudinal short can easily be obtained. Furthermore, in the lateral direction of the reflecting surface 4 D, the lateral dimension of the reflector 3 D can be minimized by the substantially hyperboloidal surface that is smaller than the lens 1 D.

In the fourth embodiment, the convex shape of the lens 1 C in vertical cross section here indicates a shape having an optical function that refracts an incident light in a direction in which the light is converged from the optical axis S in the vertical cross section of the lens ID. Therefore, the convex shape includes a shape having a convex shape only in one side as shown in FIG. 49A , a shape having a concave shape in one side and a convex shape in the other side whose degree of curve is greater than that of the concave shape as shown in FIG. 49B , and a shape inclined with respect to the optical axis S as shown in FIG. 49 C.

In the first, second, third, and fourth embodiments, NURBS as a free curved surface for light distribution is formed on each front surface and rear surface of the lenses 1 A, 1 B, 1 C, and 1 D. In this invention, however, the free curved surface for light distribution or the torus curved surface other than NURBS may be formed on the front surface and rear surface of the lenses 1 A, 1 B, 1 C, and 1 D.

In this invention, NURBS as the free curved surface for light distribution, free curved surface, or the torus curved surface may be formed on either the front surface or the rear surface of the lenses 1 A, 1 B, 1 C, and 1 D.

Further, in this invention, NURBS as the free curved surface for light distribution, free curved surface, and the torus curved surface may not be formed on the front surface and rear surface of the lenses 1 A, 1 B, 1 C, and 1 D.