JP4387783B2 - Projector type headlight - Google Patents

Description

  The present invention relates to a technique for forming a light distribution pattern that is sufficiently diffused in a horizontal direction by designing the shape of a lens surface in a projector-type headlamp including a projection lens.

  A projector-type headlamp equipped with a light source, a reflecting mirror, and a projection lens uses an ellipse-based reflecting surface. A light source is placed at the first focal position of the reflecting surface, and reflected light is reflected at the second focal point of the reflecting surface. Gather. In the low beam irradiation headlamp, a light shielding member (so-called shade) is arranged in the vicinity of the second focal position to shield unnecessary light for light distribution, and then the pattern is projected forward by the projection lens. .

  A plano-convex lens is used as the projection lens. For example, when the front surface (exit surface) is aspherical, spherical aberration can be removed. Further, a configuration in which the lens back surface (incident surface) is a concave surface is known (for example, see Patent Document 1).

  In addition, there is known an example in which a cylindrical lens for diffusion in the vertical direction is formed on the exit surface of the projection lens and a cylindrical lens for diffusion in the horizontal direction is formed on the incident surface (see, for example, Patent Document 2).

JP 2003-123519 A

Japanese Utility Model Publication No. 4-106802

  By the way, the conventional projector type headlamp has a problem that it is difficult to sufficiently secure a horizontal diffusion angle with respect to a light distribution pattern irradiated forward by the projection lens.

  For example, in a plano-convex lens having an aspherical exit surface, when it is desired to obtain irradiation light having a diffusion angle of a certain level or more in the left-right direction (horizontal direction), the incident light is incident on the back surface (plane) at a shallow angle. The surface reflection of the emitted light becomes a problem, and this becomes a factor that limits the diffusion. Therefore, by making the incident surface concave, it is possible to suppress a certain amount of surface reflection with respect to the lens cross section in the vertical plane including the optical axis, but regarding the lens cross section in the horizontal plane including the optical axis. It is difficult to reduce surface reflection at the incident surface.

  Further, total reflection on the inner surface of the projection lens is a problem. An increase in the total amount of reflected light causes a decrease in the luminous flux used, which causes a shortage of the amount of light, and causes problems such as a reduction in the size and weight of the projection lens.

  When applied to a low-beam light distribution headlamp, the effect of the shape of the projection lens on the light distribution is the formation of a cut line (or cut-off) that defines the light / dark boundary in the light distribution pattern. Is done. In other words, if the cut line cannot be formed clearly, the standard will not be compliant or there will be a problem with visibility, but the conventional lens shape cannot take sufficient measures, or the optical design including the lens and reflector There are problems in terms of taking too much time and development costs.

  Accordingly, an object of the present invention is to ensure sufficient light diffusibility in the horizontal direction in a projector-type headlamp, and to prevent the reduction in size and weight for that purpose.

  In order to solve the above-described problems, the present invention is a projector-type headlamp that includes a light source and a reflecting mirror and obtains a predetermined light distribution pattern using a projection lens, and has the following configuration. .

The incident surface of the projection lens is a continuous curved surface.The cross-sectional shape of the incident surface when the projection lens is cut along a horizontal plane including the optical axis is a convex curve facing the light source and the reflector, and the focal point or Refracting incident light assuming that it is emitted from a reference point and emitting it as a light beam that is parallel or substantially parallel to the optical axis.-The projection lens exit surface is a continuous convex curved surface facing the irradiation direction (light (The cross-sectional shape of the exit surface when cut along the vertical plane including the axis is a convex curve)
The cross-sectional shape of the exit surface when the projection lens is cut on a horizontal plane including the optical axis is a straight line or a convex curve.

  Therefore, in the present invention, the horizontal cross-sectional shape of the projection lens is a convex curve protruding toward the light source and the reflecting mirror so as to reduce surface reflection on the entrance surface and suppress total reflection at the exit surface boundary in the horizontal direction. It is possible to form a light distribution pattern having a sufficient spread.

  In the conventional projection lens, it was impossible to irradiate diffused light of a certain level or more due to surface reflection on the lens back surface (incident surface). However, according to the present invention, the horizontal diffusion angle with respect to the light distribution pattern is reduced. It can be secured sufficiently. In addition, it is possible to overcome the problem of insufficient light quantity due to surface reflection and total reflection in the projection lens, and to realize a projector type headlamp suitable for miniaturization and weight reduction.

  A configuration in which the vertical cross-sectional shape of the incident surface of the projection lens is a concave curve or a straight line facing the light source and the reflector side is effective in suppressing surface reflection on the incident surface. Moreover, in the form in which the vertical cross-sectional shape of the incident surface of the projection lens is a convex curve facing the light source and the reflecting mirror side, the lens can be made larger. It is also effective for increasing the light emitting area, reducing dazzling light, shortening the overall length of the lamp, and the like.

  The horizontal or vertical cross-sectional shape of the incident surface and the output surface of the projection lens has a high degree of freedom in shape design if it is a second-order or higher-order curve or aspherical cross-sectional curve. Advantages such as easy comprehensive optical design including

  Further, in the form in which the curved surface is formed by rotating the horizontal sectional shape of the incident surface with the horizontal straight line passing through the focal point or reference point on the optical axis and orthogonal to the optical axis as the central axis, The incident surface of the projection lens can be defined (the light emitted from the focal point is perpendicular to the incident surface in a vertical section). For the exit surface of the projection lens, if the vertical cross-sectional shape of the exit surface is rotated around the central axis extending perpendicularly to the optical axis, the shape design becomes simple, and the exit surface (convex surface) is simplified. Can be formed as a rotating surface.

  In consideration of the optical design and ease of manufacture of the projection lens, it is preferable that the cross-sectional shape of the lens surface is a quadratic surface, for example, the horizontal cross-sectional shape of the incident surface of the projection lens is a hyperbola, and the exit surface May be an elliptic cylinder surface (the vertical cross-sectional shape is an elliptical arc and the horizontal cross-sectional shape is a straight line).

  In addition, in application to a low beam irradiation lamp, it is set so that light emitted from a light source and reflected by a reflecting mirror is collected at a focal point or a reference point related to a projection lens. A light shielding member is arranged in the vicinity of the reference point, and a clear cut line can be formed in the light distribution pattern. That is, in order to clarify the cut line, it is preferable that the horizontal cross-sectional shape of the exit surface is a straight line or a convex curve facing the irradiation direction with respect to the horizontal cross-sectional shape of the light-incident surface.

  By making the horizontal length of the projection lens viewed from the optical axis direction relatively shorter than the vertical length, the left and right dimensions can be shortened and the lens weight can be reduced. The influence of the shortage can be reduced.

  The present invention relates to a projector (projection) type headlamp using a light source, a reflecting mirror, and a projection lens in application to a headlamp for a vehicle such as an automobile. For example, in the light distribution pattern related to the traveling beam and the passing beam, it is possible to sufficiently diffuse the light in the horizontal direction and to suppress glare caused by glare.

  1 and 2 are explanatory views of a basic configuration according to the present invention. FIG. 1 schematically shows a vertical sectional configuration including a main optical axis of a lamp indicated by an x axis, and FIG. 2 shows the main optical axis. The horizontal cross-sectional structure to be included is shown schematically.

  The projector-type headlamp 1 includes a light source 2 and a reflecting mirror 3. Examples of light sources that are simply indicated by circles in the drawing include incandescent bulbs, discharge lamps, light-emitting elements (for example, light-emitting diodes), and the like. Can be mentioned. Moreover, various curved surfaces based on an ellipse are used for the reflecting surface of the reflecting mirror 3, for example, a rotating ellipsoid, a curved surface combining a parabola and an ellipse (so-called parabolic-elliptical compound surface), A free-form surface or an aspherical surface that cannot be expressed by an analytical single function can be used.

  In this example, the light source 2 is positioned on the optical axis (x-axis), and after being emitted from the light emitting portion, the light reflected by the reflecting mirror 3 is directed toward the projection lens 4 disposed forward. However, in application of the present invention, the present invention is not limited to such an example, and a configuration in which the light source 2 is not disposed on the main optical axis of the lamp, for example, with respect to the optical axis of the reflector Thus, the present invention can be applied to a mode (so-called “lateral insertion type”) in which a light source is inserted from a direction orthogonal to each other and a light emitting portion of the light source is set at a predetermined position in a reflecting mirror.

  Further, in application to a low beam, a light shielding member (so-called shade) 5 for forming a cut line in the light distribution pattern is required, and the upper edge portion is light between the reflecting mirror 3 and the projection lens 4. It arrange | positions so that an axis | shaft may be touched. In this example, a rectangular plate-shaped light shielding member is illustrated for convenience, but a curved light shielding member is used as necessary.

  A projection lens (or a condensing lens) 4 formed of glass or synthetic resin is disposed on the x-axis with a predetermined distance forward from the reflecting mirror 3 (hereinafter referred to as the irradiation direction).

  The incident surface 4Si of the projection lens 4 is a continuous curved surface and is preferably not a discontinuous composite surface. Examples of the vertical cross-sectional shape thereof include the following modes.

(I) Concave curve or straight line facing the light source 2 and the reflecting mirror 3 side (straight line orthogonal to the x axis or inclined with respect to the x axis)
(II) A convex curve facing the light source 2 and the reflecting mirror 3 side.

  In the example shown in FIG. 1, the vertical cross-sectional shape of the reflecting surface of the reflecting mirror 3 is an ellipse, and the light from the reflecting mirror 3 is incident on the incident surface 4Si. For example, in order to reduce the surface reflection of the incident light on the lens periphery, it is preferable to reduce the incident angle with respect to the normal line on the incident surface as described in (I) above. That is, in the vertical section, the incident angle “φa” related to the concave curve 6 indicated by the solid line is smaller than the incident angle “φb” related to the straight line 7 indicated by the alternate long and short dash line, and therefore the amount of surface reflection is reduced.

  Further, when there is no particular problem with the surface reflection, the convex curve 8 (see the two-dot chain line) facing backward can be used as in (II) above, which is effective when the projection lens 4 is desired to be enlarged. It is. Further, the light emitting area can be increased without significantly increasing the thickness, and the luminance of the light emitting portion can be reduced to reduce dazzling light.

  Examples of the horizontal cross-sectional shape of the incident surface 4Si include the following forms.

(1) Straight lines (straight lines perpendicular to the x axis, etc.)
(2) A convex curve facing the light source 2 and the reflecting mirror 3 side.

  In the example shown in FIG. 2, the horizontal cross-sectional shape of the reflecting surface of the reflecting mirror 3 is an ellipse, or a curve having an intermediate action between an elliptical optical action and a parabolic optical action. Is incident on the incident surface 4Si. For example, in order to reduce the surface reflection of the incident light on the lens periphery, it is preferable that the horizontal sectional shape of the incident surface 4Si is not a concave curve facing backward. That is, it is preferable to reduce the incident angle with respect to the normal line on the incident surface, such as the straight line shown in (1) above, and the convex curve facing backward shown in (2) above. In the horizontal section, the incident angle “θa” related to the convex curve 9 indicated by the solid line is smaller than the incident angle “θb” related to the straight line 10 indicated by the alternate long and short dash line, so the surface reflection amount is reduced. On the other hand, when the incident surface 4Si is a concave curved surface (for example, a spherical surface) facing backward, surface reflection can be suppressed in the vertical section, but surface reflection can be sufficiently suppressed in the horizontal section. Is difficult.

  Therefore, in the present invention, the cross-sectional shape of the incident surface when the projection lens 4 is cut on a horizontal plane including the optical axis (x axis) is a convex curve facing the light source 2 and the reflecting mirror 3 side. Then, the incident light assuming that it is emitted from the focal point or the reference point (condensing reference point) of the curve is refracted at the incident surface (boundary surface), and the light beam parallel to the optical axis or an allowable set angle. It is emitted as a substantially parallel light beam within the range. That is, the shape of the convex curve is defined based on the target optical action in relation to the exit surface shape of the projection lens 4. As a general curvature tendency, the curvature is large in the region near the optical axis, and the curvature is small in the peripheral region.

  In addition, an example in which the horizontal cross-sectional shape of the incident surface 4Si is a convex curve rather than a straight line is an example in which the size of the projection lens is relatively larger than the size of the reflecting mirror. If the lens diameter of the projection lens is larger than the aperture diameter of the reflecting mirror, if the horizontal cross-sectional shape of the entrance surface is a straight line, the exit angle at the refraction boundary will be limited, but it will be horizontal as a convex curve facing backwards. By defining the cross-sectional shape, the horizontal diffusion angle can be increased.

  As shown in FIG. 1, the exit surface (or exit surface) 4So of the projection lens 4 is preferably a continuous convex curved surface facing the irradiation direction, and has a cross-sectional shape when cut along a vertical plane including the x-axis. A convex curve 11 is assumed.

  And about the cross-sectional shape of the output surface 4So when the projection lens 4 is cut | disconnected by the horizontal surface containing x-axis, it is preferable that it is a straight line or convex curve orthogonal to x-axis.

  FIG. 3 is a diagram for explaining the horizontal cross-sectional shape of the projection lens 4, and the horizontal cross-section of the incident surface 4 Si is a convex curve facing the direction (backward) indicated by the arrow B.

  As for the horizontal cross-sectional shape of the exit surface 4So, a straight line indicated by “SL” or a convex curve directed in the direction of the arrow A (forward) as indicated by “SA” in consideration of application to a passing beam ( For example, an arc having a radius of curvature within an allowable range is preferable. This is to form the cut line clearly, and it has been found that the cut line tends to be disturbed when a concave curve directed in the direction of the arrow B is adopted, as indicated by “SB”. (In contrast to the light-incident incident surface horizontal cross-sectional curve, if the output surface horizontal cross-sectional shape is a concave curve, it has a reverse action (divergence)). In application to a traveling beam, it is also possible to use a concave curve as shown in “SB” (however, it is necessary to prevent the curvature from becoming excessively large with respect to the problem of mold workability due to the concave portion. is there.).

  In the example shown in FIG. 2, the horizontal sectional shape of the exit surface is a convex curve 12 facing forward, but when this is a straight line orthogonal to the x-axis, the convex curve 11 of FIG. A cylindrical surface is formed as a locus when moved in the horizontal direction perpendicular to the x-axis (a specific example will be described later). In any form, the shape design is performed so as to sufficiently reduce the total reflected light amount on the exit surface 4So.

  In the vertical cross section of the projector-type headlamp 1 (see FIG. 1), the light emitted from the light emitting portion of the light source 2 is reflected by the reflecting mirror 3 and then converged toward the focal point or reference point related to the projection lens 4. Is done. For example, in FIG. 1, when the vertical cross-sectional shape of the reflecting surface is an elliptical arc and the light source 2 is positioned at the first focal point, the reflected light is the second focal point (which coincides with the focal point or reference point of the lens). It is condensed toward Then, the shape of the cut line is defined by the upper edge portion of the light shielding member 5 disposed in the vicinity of the focal point, and is projected forward through the projection lens 4.

  Further, in the horizontal section of the projector-type headlamp 1 (see FIG. 2), among the light emitted from the light emitting unit of the light source 2, the light reflected by the paraxial region of the reflecting mirror 3 is the optical axis (x-axis). ), And passes through the central portion of the projection lens 4, but the light reflected at the peripheral portion of the reflecting surface away from the paraxial region is projected at a relatively large angle with respect to the x-axis. The light enters the lens 4.

  FIGS. 4 to 12 show examples of the shape of the projection lens according to the present invention. For example, the forms shown below with respect to the incident surface can be mentioned.

(A) A form in which the horizontal cross-sectional shape is a convex curve and the vertical cross-sectional shape is a straight line. (B) A form in which both the horizontal cross-sectional shape and the vertical cross-sectional shape are convex curves.

  4 to 7 show configuration examples of the above-described form (A). 4 is a front view of the projection lens 4A viewed from the optical axis direction, a vertical sectional view (longitudinal sectional view taken along line AA) on the right side thereof, and a horizontal sectional view (cross sectional view taken along line BB) below. The shape of a conventional projection lens AS (a plano-convex lens having an aspheric front surface) is shown in comparison with a one-dot chain line. 5 and 6 are perspective views, and FIG. 7 is a side view of the projection lens 4A viewed from the horizontal direction orthogonal to the optical axis.

  As shown in the front view of FIG. 4, the projection lens 4 </ b> A has a shape close to an ellipse that is slightly expanded in the horizontal direction as compared with the conventional aspherical lens AS (front shape is circular).

  In this example, the cross-sectional shape when cut along a vertical plane including the optical axis with respect to the incident surface 13 of the projection lens 4A is a straight line 13v, and the cross-sectional shape when cut along the horizontal plane including the optical axis is the light source and the reflecting mirror. The convex curve 13h is directed to the side.

  And regarding the exit surface 14 of the projection lens 4A, the cross-sectional shape when cut along the vertical plane including the optical axis is a convex curve 14v facing the irradiation direction, and the cross-sectional shape when cut along the horizontal plane including the optical axis is The convex curve 14h faces the irradiation direction. For example, the vertical cross-sectional shape is a convex curve (aspherical cross-sectional curve, etc.) facing forward, and the convex curve is formed as a locus when rotated with the vertical axis orthogonal to the optical axis as the central axis. A curved surface can be used. In other words, the convex curved surface can be defined as the rotation surface by rotating the vertical cross-sectional shape of the exit surface around the central axis that is orthogonal to the optical axis and extends in the vertical direction.

  5 shows the exit surface 14 when the projection lens 4A is viewed obliquely from the front, and FIG. 6 shows the entrance surface 13 and the exit surface 14 from different viewpoints.

  The vertical cross-sectional shape of the incident surface 13 is not limited to the straight line 13v shown in FIGS. 4 and 7, but may be a concave curve 13v ′ facing rearward as in the projection lens 4A ′ shown in FIG.

Examples of the horizontal cross-sectional shape or vertical cross-sectional shape of the incident surface 13 and the output surface 14 include secondary or higher-order curves and aspherical cross-sectional curves. For example, in the latter case, the formula that gives the deviation from the quadratic curve (conical curve) is the simplest, and the curved surface expressed by a formula obtained by adding a higher-order correction term to the quadratic curved surface formula is “ X = (c · H ² ) / (1 + √ (1−k · c ² · H ² )) + Σ (a _i · H ⁱ ) ”. Here, “X” indicates a position on the x-axis, “c” is the curvature at the apex, and “k” is a conic constant. Regarding the two axes orthogonal to the x-axis, when the position coordinates of each axis are denoted as “Y” and “Z”, respectively, “H ² = Y ² + Z ² ”. “Σ” means a term sum for the natural number variable “i”, and “a _i ” indicates the i-th aspheric coefficient. The aspherical cross-section curve is a curve that is formed when the aspheric surface is cut by a plane including the x-axis.

  In addition to this, a method of expressing an aspheric surface by a spline function or the like is known, and generally a shape design using a free curve (third-order or higher Hermitian interpolation curve, Bezier curve, B-spline curve, etc.) Is done. That is, since the degree of freedom in shape design is high compared to the method of defining the cross-sectional shape using a quadratic curve, the design including the optical relationship with the reflective surface shape is possible. For example, when the lens surface is limited to a quadratic curved surface, if the shape design of the reflecting surface or the like is difficult due to the narrow range of shape change, the advantage is that the design can be facilitated by using a free curve etc. Is obtained. Depending on the CAD (Computer Aided Design) system to be used, the cross-sectional shape can be designed using parametric polynomial curves or rational polynomial curves with various free curves, but not limited to this, non-parametric representation (The numerical expression format is not limited as long as basic calculations such as points on the curved surface and normal vectors are possible.)

In addition, the continuity of the cross-sectional curve is preferably not less than first-order continuity (differential continuity or tangent continuity). That is, in the case of a broken line formed by connecting a large number of line segments, there is a risk of affecting the optical effect due to the C ⁰ class connection point or the processability of the lens surface. However, when multiple areas are designed separately for different purposes and functions and curved surfaces related to each area are connected, discontinuous lines less than the first-order continuity may occur. Needless to say, it is allowed as long as there is no problem. The lens material is preferably a transparent synthetic resin in view of high molding accuracy.

  9 to 12 show configuration examples of the above-described form (B). 9 is a front view of the projection lens 4B viewed from the optical axis direction, a vertical sectional view (longitudinal sectional view indicated by AA line) on the right side, and a horizontal sectional view (transverse line indicated by BB line) below. The shape of a conventional projection lens AS (a plano-convex lens having an aspheric front surface) is shown in comparison with a one-dot chain line. 10 and 11 are perspective views, and FIG. 12 is a side view of the projection lens 4B as viewed from the horizontal direction orthogonal to the optical axis.

  As shown in the front view of FIG. 9, the projection lens 4B is slightly larger than the conventional aspherical lens AS, but has a shape close to an ellipse extending in the horizontal direction compared to the vertical direction.

  In this example, the cross-sectional shape when cut along the vertical plane including the optical axis with respect to the incident surface 15 is a convex curve 15v facing the light source and the reflector, and the cross-sectional shape when cut along the horizontal plane including the optical axis is as follows. The convex curve 15h faces the light source and the reflector side.

  And regarding the output surface 16, the cross-sectional shape when it cut | disconnects by the perpendicular surface containing an optical axis is made into the convex curve 16v which faced the output direction. Moreover, the cross-sectional shape when cut along a horizontal plane including the optical axis is a convex curve 16h facing the emission direction. Also in this example, the convex curved surface can be defined as the rotational surface by rotating the vertical cross-sectional shape of the exit surface around the central axis perpendicular to the optical axis and extending in the vertical direction (relative to the convex curve 14h). In a typical comparison, the curvature is small.)

  10 shows the exit surface 16 when the projection lens 4B is viewed obliquely from the front, and FIG. 11 shows the entrance surface 15 and the exit surface 16 from different viewpoints.

  As for the horizontal sectional shape or the vertical sectional shape of the incident surface 15 and the emitting surface 16 shown in this example, a higher-order curve of a second or higher order, an aspherical sectional curve, or the like can be used as described above.

  In each of the examples described above, a shape having symmetry with respect to a horizontal section and a vertical section including the optical axis has been described. However, application of the present invention is not limited to such a form. For example, in order to improve vehicle mountability, it is also possible to produce a projection lens having asymmetry in the left and right (horizontal direction) or up and down (vertical direction), and the following application forms are mentioned.

-Left-right asymmetric form-Up-down asymmetric form-Left-right and up-down asymmetric form (for example, a shape adapted to the lens surface shape of the outer lens).

  13 and 14 show an example of a projection lens having asymmetry in the horizontal direction. 13 is a front view of the projection lens 4C viewed from the optical axis direction, a vertical sectional view (longitudinal sectional view shown by AA line) on the right side, and a horizontal sectional view (transverse line shown by BB line) below. Area diagram). FIG. 14 is a perspective view of the emission surface when viewed obliquely from the front.

  In the projection lens 4 </ b> C shown in the front view of FIG. 13, the optical axis passes through the intersection of the AA line and the BB line and extends in a direction perpendicular to the paper surface. The intersection position between the optical axis and the exit surface is located on the left side of the figure from the center position in the horizontal direction.

  In this example, the cross-sectional shape when cut along the vertical plane including the optical axis with respect to the incident surface 17 is a concave curve 17v (or a straight line) facing the light source and the reflector, and when cut along the horizontal plane including the optical axis. The cross-sectional shape is a convex curve 17h facing the light source and reflector side.

  The exit surface 18 is a curved surface inclined with respect to the optical axis so as to be adapted to the vehicle body shape of the vehicle. In this example, the cross-sectional shape when cut along a vertical plane including the optical axis is a convex curve 18v facing the emission direction. Further, when the cross-sectional shape when cut along the horizontal plane including the optical axis is a convex curve 18h facing the emission direction, and an arbitrary point on the curve is denoted as "P", this is one end point PR (right end of the figure) From the point) to the other end point PL (the left end point in the figure), the angle of the tangent vector at the point P with respect to the optical axis gradually decreases. In the case of a lamp provided on the left side of the front part of the vehicle as viewed from the direction along the vehicle traveling direction, the right end of the lamp is a convex curve or straight line positioned forward of the left end in the horizontal section of the lens exit surface. In the case of a lamp provided on the right side of the front portion of the vehicle, the opposite is true (the left end of the lamp is a convex curve or straight line positioned forward of the right end in the horizontal section).

  Of course, it is possible to use a projection lens having asymmetry in the vertical direction in consideration of adapting to the slanting of the front shape of the vehicle body (increasing the inclination angle of the front surface in order to reduce air resistance, etc.). is there. In this case, like the projection lens 4D shown in FIG. 15, the exit surface 19 is designed to match the vehicle body shape of the vehicle, and is a convex curved surface inclined with respect to the vertical plane orthogonal to the optical axis. .

  In the actual design of the projection lens, the exit surface is determined first based on the curved surface of the lens design, and the shape of the entrance surface is often determined according to the shape of the exit surface (the entrance surface and the exit surface are They are designed independently and are not arbitrarily combined.)

  As described above, the cross-sectional shape of the entrance surface and the exit surface is generally expressed in a curved form such as a free curve, and it is difficult to recall a curved surface shape, but has symmetry with respect to the plane including the optical axis, As a relatively simple shape example, there is a rotating surface formed as a locus when a quadric surface or a quadratic curve is rotated around a predetermined central axis.

  In the following, the horizontal cross-sectional shape of the incident surface of the projection lens is a hyperbola, the incident surface is defined as a rotation surface with a horizontal straight line orthogonal to the optical axis as the central axis, and the exit surface of the projection lens is an elliptic cylinder surface. A configuration example of an aspheric lens in which spherical aberration is eliminated will be described with reference to FIGS.

  16 and 17 schematically show a configuration example 20 of the projector-type headlamp. FIG. 16 shows a vertical cross-sectional configuration, and FIG. 17 shows a horizontal cross-sectional configuration.

  In FIG. 16, the light emitting part of the light source 2 is positioned on the optical axis (x axis), and the reflecting mirror 3 (elliptical reflecting mirror) is provided. In the low beam lamp, the light shielding member 5 is disposed in front of them. Further, a projection lens 4E is arranged in front of it.

  In the projection lens 4E, the vertical cross-sectional shape of the incident surface 4Si is an arc, and the vertical cross-sectional shape of the output surface 4So is an elliptical arc.

  Further, as shown in FIG. 17, the horizontal cross-sectional shape of the incident surface 4Si is a hyperbola, and the horizontal cross-sectional shape of the output surface 4So is a straight line orthogonal to the optical axis.

  FIG. 18 is a diagram for explaining an example of the shape of the projection lens 4E. A horizontal sectional view is shown above the front view, and a vertical sectional view is shown to the right of the front view.

  “Wv” shown in the front view indicates the vertical width (that is, the width in the vertical direction) of the projection lens 4E, and “Wh” indicates the horizontal width (that is, the width in the horizontal direction) of the projection lens 4E. In this example, the front shape of the projection lens 4E is close to a square, and the aspect ratio (or rectangular ratio) “Wv / Wh” is close to 1, but the left and right peripheral portions of the lens are Considering that it is not so much used compared to the central part (most of the light from the reflecting mirror is transmitted near the center of the lens near the optical axis), the peripheral part should be cut so that Wv> Wh. Is possible. That is, if the horizontal length of the projection lens as viewed from the optical axis direction is designed to be shorter than the vertical length, it is effective in reducing the weight and size of the lens (shortening the left and right dimensions). Of the components of the projector type headlamp, the light emitting surface of the projection lens appears on the exterior of the vehicle, and a vertically long design with a smaller Wh than Wv is possible. For example, a minimum value of Wh is about 40 mm, and a lens having a Wv of about 60 mm (an aspect ratio value of about 1.5) can be manufactured.

  In the horizontal cross section, the shape of the entrance surface 4Si is a hyperbola 21, and the shape of the exit surface 4So is a straight line 22 orthogonal to the x-axis.

  “Y-axis” in the figure indicates an axis (horizontal axis) orthogonal to the x-axis in the horizontal plane including the x-axis, and the intersection “A” between the x-axis and the y-axis is the focal point (or reference point) related to the incident surface. ). That is, assuming that a point light source is placed at point A, the light emitted from this point is refracted at the incident surface boundary (hyperbola 21) to become a substantially parallel light beam, and has a power at the output surface boundary (horizontal section). No).

  The incident surface 4Si is formed as a rotation surface formed by rotating the hyperbola 21 with the y axis (the horizontal axis passing through the point A) as the rotation center axis.

  That is, in the vertical cross section, the shape of the incident surface 4Si is a part (arc) 23 of a circle (refer to the great circle “γ” indicated by a dashed line in the drawing) centered on the point A (center of curvature).

  Further, in the vertical cross section, the shape of the exit surface 4So is a part (elliptical arc) 24 of an ellipse (see an ellipse “ε” indicated by a broken line in the figure) having the point A as the first focal point (F1) (in the figure). The point “F2” indicates the second focal point (both elliptical focal points F1 and F2 are located on the optical axis).

  The emission surface 4So has a cylindrical shape formed as a locus when the elliptical arc 24 is translated along a direction parallel to the y-axis.

  Assuming that a point light source is placed at point A in the vertical cross section, the light emitted from this point is perpendicularly incident on the incident surface boundary (arc 23) and refracted at the output surface boundary (elliptical arc 24) to be substantially parallel. It becomes a light beam and is emitted toward the front.

  FIG. 19 is a perspective view of the projection lens 4E as viewed obliquely from the front. The exit surface 4So has a cylindrical shape and both ends in the horizontal direction are cut.

  FIG. 20 is a perspective view of the projection lens 4E when viewed obliquely from the rear, and has a shape in which the incident surface 4Si is a bowl-shaped surface, the center portion is recessed, and the portions near both the upper and lower ends protrude rearward.

  FIG. 21 shows a ray tracing diagram of the radiated light from the point light source with the point A as the focal point, showing the horizontal section of the lens on the upper side and the vertical section on the lower side.

  The substantial refraction boundary in the horizontal section is a hyperbola 21, and it can be seen that light is collimated in the horizontal direction only by the refraction action of the incident surface. Since the exit surface has no power in the horizontal direction, when the entrance surface is regarded as the main surface, the intersection between the hyperbola 21 and the x-axis is the main point, and the focal length “fh” is the distance from this point to the A point. Is decided.

  Further, it can be seen that the substantial refraction boundary in the vertical section is the elliptical arc 24, and the light that is perpendicularly incident on the arc 23 and spreads upward and downward is parallelized in the vertical direction only by the refraction action of the exit surface. That is, when the exit surface is regarded as the main surface, the intersection (vertex) between the elliptical arc 24 and the x-axis is the main point, and the focal length “fv” is determined as the distance from this point to the A point.

  The relationship “fv> fh” is suitable for the formation of a vehicle light distribution pattern (the longer the focal length, the smaller the image is projected, so the light is diffused in the horizontal direction, which has a shorter focal length than in the vertical direction. Can be made.)

  For example, as a method for examining lens characteristics, a method of observing a projection pattern by simulation or the like when a grid-like light emitter is positioned near a focal point and the light emitter is projected by a lens is known. When the projection lens 4E is used, the grid is projected on the front screen over a wide range, and the grid spacing is different in the vertical direction (vertical direction) and the horizontal direction (horizontal direction). This is due to the difference in focal length between the horizontal sectional shape of the incident surface of the projection lens and the vertical sectional shape of the exit surface (fh <fv). Since the light distribution for vehicles requires a pattern extending in the horizontal direction compared to the vertical direction, the focal length related to the cross-sectional shape when the incident surface of the projection lens is cut on the horizontal plane including the optical axis is emitted. It is preferable that the focal length be shorter than the vertical cross-sectional shape of the surface.

  On the other hand, when a conventional plano-convex lens having an aspherical exit surface is used, the projection pattern (image) on the front screen shows a typical barrel distortion, and the lattice spacing on the top, bottom, left and right is equal. (Square lattice image).

  As described above, the projection lens 4E has a characteristic of converting the radiated light from the point A into parallel light and irradiating it forward.

  In this example, since the exit surface is an elliptic cylinder surface and the horizontal cross-sectional shape is a straight line, the horizontal cross-sectional shape of the incident surface is a specific hyperbola (the eccentricity is the refractive index n, the geometrical The second focus is the optical focus.) The hyperbola is determined by the refractive index of the lens and the back focal length (distance from the focal point to the lens surface). Further, the incident surface is a rotating surface using a hyperbola, and an elliptical arc is used so that light emitted from the focal point A in the vertical section is refracted on the line of the exit surface boundary to become parallel light (the eccentricity of the ellipse is Equal to the reciprocal of the refractive index n). The elliptical arc is determined by the refractive index of the lens and the focal length (distance from the focal point to the lens apex), and the upper and lower limits are determined as the intersection of the ellipse ε and the circle γ shown in FIG.

  When the exit surface has a cylindrical shape and the horizontal cross-sectional shape is a straight line as in this example, the horizontal cross-sectional shape of the entrance surface is defined as a hyperbola, but in general, the horizontal cross-sectional shape of the exit surface is a straight line. In this case, the horizontal cross-sectional shape of the incident surface is a curved shape that is difficult to express with an analytical function (presents a lens surface using a free-form surface).

  FIG. 22 is an explanatory diagram of a horizontal cross section schematically showing the reflecting mirror and the projection lens.

  The refraction boundary of the projection lens 4E is a hyperbola 21 and a straight line 22 indicated by a solid line in the figure, and the straight line 25 and a convex curve (aspherical cross-section curve) indicated by a two-dot chain line are contrasted with a refraction boundary of a conventional plano-convex lens. Show.

  The light emitting unit of the light source 2 is located at the first focal point “F1” of the reflecting mirror 3, and light emitted from the focal point and then reflected at the point “R” on the reflecting surface of the reflecting mirror 3 is projected. Proceed toward the entrance surface of the lens.

  A point “Pi” on the hyperbola 21 indicates an incident point, and a case of normal incidence is illustrated for easy understanding. On the other hand, the point “Q” indicates an incident point on the straight line 25 and is incident on the plane with an incident angle indicated by “θ” in the drawing. That is, it is clear that the incident angle to the hyperbola 21 is smaller than θ, and it can be seen that the amount of surface reflection light is reduced.

  FIG. 23 schematically shows a light distribution pattern 27 of a passing beam when the present invention is applied, in comparison with a conventional pattern indicated by a broken line, and an “HH” line in the figure is a horizontal line. The “V-V” line indicates a vertical line.

  The amount of surface reflected light on the incident surface of the projection lens is reduced, and a light distribution pattern 27 having a larger horizontal diffusion angle than the conventional one can be obtained (see “α” in the figure).

  For example, with respect to the light distribution distribution of the passing beam, when the conditions such as the light source and the reflecting mirror are set to the same setting, the horizontal diffusing angle can be increased by about 30 ° (15 ° each) in total on the left and right as compared with the conventional case. Thus, it is possible to guarantee sufficient horizontal diffusion only by the action of the projection lens without requiring a diffusion lens step or the like.

  Thus, road surface illumination can be performed with wide diffused light in the horizontal direction in the vehicle headlamp light distribution, so that visibility of curved roads, intersections, road shoulders, and the like can be improved, and nighttime driving safety can be improved. Further, by sufficiently increasing the horizontal diffusion angle of the headlamp, there is an advantage that it is not necessary to use an auxiliary headlamp such as a fog lamp or a cornering lamp.

  Next, the total reflection on the lens exit surface will be described. The point “Po” in FIG. 22 is located on the straight line 22 or the convex curve 26, and the angle formed by the outgoing light beam passing through the point with respect to the x axis is “φ”. Is shown.

  In the case of the convex curve 26, if the incident angle of the light ray with respect to the normal line at the point Po is large, loss light due to total reflection is generated, leading to a decrease in the used light beam. In the case of the straight line 22, the method at the point Po is used. Since the incident angle of the light ray with respect to the line is small and the light is emitted out of the lens without being totally reflected, the light flux used is increased as compared with the conventional case. In other words, out of the light that is reflected by the portion near the periphery of the reflecting mirror and then incident on the incident surface of the projection lens, the light that has been previously lost by total reflection at the exit surface must be used effectively. Can do.

  According to the configuration described above, it is possible to increase the front projection area (effective area) of the projection lens, and to sufficiently diffuse in the horizontal direction so that the center of light intensity in the light distribution pattern does not become excessively bright. By securing light, dazzling light due to glare can be reduced. In addition, since the optical lens has little optical influence even when the left and right peripheral edges of the projection lens are cut off, a novel lamp design can be realized by designing the front shape to be rectangular, and by shortening the left and right width, The lens can be made smaller and lighter.

  In the above configuration, for the sake of convenience of explanation, a single projection lens is used. However, the application of the present invention is not limited to such an example. For example, as shown in FIGS. In addition, a projection lens provided with a plurality of lens portions having different shapes, focal positions, and the like can be used.

  That is, in the projection lens 4F shown in FIG. 24, the two lens portions 28 and 29 are arranged along the horizontal direction. For example, one lens portion 28 is used for a traveling beam and the other lens portion 29 is a passing beam. It is for use. The exit surface 4So common to the entrance surfaces of the lens units is a continuous surface (for example, a convex curved surface whose curvature does not locally exceed a predetermined value). Further, in the projection lens 4G shown in FIG. 25, two lens portions 30 and 31 are arranged along the vertical direction, one of them (for example, the lens portion 31) is used for a traveling beam, and the other lens portion is a passing beam. It is used. And the output surface 4So used as a continuous surface is made common with respect to the entrance surface of each lens part.

  The material of these projection lenses is preferably plastic in consideration of shape accuracy, and has an advantage that a mounting portion (mounting portion, etc.) for fixing the lens to a reflecting mirror or the like can be integrally formed with the lens body. Is obtained.

It is explanatory drawing of the basic composition which concerns on this invention with FIG. 2, This figure is a figure which shows a vertical cross-sectional structure. It is a figure which shows a horizontal cross-section structure. It is a figure for demonstrating the horizontal cross-sectional shape of a projection lens. It is a figure which shows an example of a projection lens with FIG. 5 thru | or FIG. 7, and this figure is a figure which shows a front shape and a cross-sectional shape. It is a perspective view of a projection lens. FIG. 6 is a perspective view of the projection lens viewed from a direction different from that in FIG. 5. It is a side view of a projection lens. It is a side view which shows another example of a projection lens. It is a figure which shows another example about the shape of a projection lens with FIG. 10 thru | or FIG. 12, and this figure is a figure which shows a front shape and a cross-sectional shape. It is a perspective view of a projection lens. It is a perspective view of the projection lens seen from the direction different from FIG. It is a side view of a projection lens. It is a figure which shows another example about the shape of a projection lens with FIG. 14, This figure is a figure which shows a front shape and a cross-sectional shape. It is a perspective view of a projection lens. It is a vertical sectional view showing another example of the projection lens. It is a figure which shows roughly the structural example of a projector type headlamp with FIG. 17, This figure is a figure which shows a vertical cross-sectional structure. It is a figure which shows a horizontal cross-section structure. FIGS. 19 and 20 together with FIGS. 16 and 17 show examples of the shape of the projection lens constituting the projector-type headlamp, and this figure shows the front shape and the cross-sectional shape. It is a perspective view of a projection lens. It is a perspective view of the projection lens seen from the direction different from FIG. The ray tracing diagram regarding the radiated light from a point light source is illustrated, a horizontal cross section is shown above, and a vertical cross section is shown below. It is explanatory drawing in the horizontal cross section which showed the reflective mirror and the projection lens substantially linearly. It is a figure for demonstrating the light distribution pattern of a passing beam. It is a perspective view which shows an example of the projection lens provided with the several lens part. It is a perspective view which shows another example of the projection lens provided with the several lens part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector type headlamp, 2 ... Light source, 3 ... Reflection mirror 4, 4A, 4A ', 4B, 4C, 4D, 4E, 4F, 4G ... Projection lens, 4Si ... Incidence surface, 4So ... Output surface, 5 ... light-shielding member, 6 ... concave curve, 7 ... straight line, 8 ... convex curve, 9 ... convex curve, 12 ... convex curve, 13 ... incident surface, 13h ... convex curve, 13v ... straight line, 13v '... concave curve, 14 ... Exit surface, 14h, 14v ... convex curve, 15 ... entrance surface, 15h, 15v ... convex curve, 16 ... exit surface, 16h, 16v ... convex curve, 17 ... entrance surface, 17h ... convex curve, 17v ... concave curve, 18 ... emission surface, 18h, 18v ... convex curve,
DESCRIPTION OF SYMBOLS 19 ... Outgoing surface, 20 ... Projector type headlamp, 21 ... Hyperbola, 22 ... Straight line

Claims (8)

In a projector type headlamp that includes a light source and a reflecting mirror and obtains a predetermined light distribution pattern using a projection lens,
The incident surface of the projection lens is a continuous curved surface, and the sectional shape of the incident surface when the projection lens is cut on a horizontal plane including the optical axis is a convex curve facing the light source and the reflector side, and the focal point thereof Or refracting incident light when it is assumed that the light is emitted from a reference point and emitting it as a light beam parallel or substantially parallel to the optical axis,
The vertical cross-sectional shape of the incident surface of the projection lens is a concave curve facing the light source and the reflector side,
The exit surface of the projection lens is a continuous convex curved surface facing the irradiation direction, and the sectional shape of the exit surface when the projection lens is cut along a horizontal plane including the optical axis is a straight line or a convex curve. Characteristic projector-type headlamp. In the projector type headlamp according to claim 1 ,
A projector-type headlamp, wherein a horizontal sectional shape or a vertical sectional shape of an incident surface of the projection lens is a second-order or higher-order curve or an aspherical sectional curve. In the projector type headlamp according to claim 1 or 2 ,
The curved surface is formed by rotating the horizontal sectional shape of the incident surface of the projection lens with the horizontal straight line passing through the focal point or reference point on the optical axis and orthogonal to the optical axis as the central axis. Projector type headlight. In the projector type headlamp according to any one of claims 1 to 3 ,
A projector-type headlamp, wherein a horizontal sectional shape or a vertical sectional shape of an exit surface of the projection lens is a second-order or higher-order curve or an aspheric sectional curve. In the projector type headlamp according to any one of claims 1 to 4 ,
A projector-type headlamp, wherein the convex curved surface is formed by rotating a vertical cross-sectional shape of an exit surface of the projection lens around a central axis perpendicular to an optical axis and extending in a vertical direction. In the projector type headlamp according to claim 3 ,
A projector-type headlamp, wherein a horizontal sectional shape of an incident surface of the projection lens is a hyperbola, and an exit surface of the projection lens is an elliptic cylinder surface. The projector type headlamp according to any one of claims 1 to 6 ,
The light emitted from the light source and reflected by the reflecting mirror is collected at the focal point or reference point, and a light shielding member is disposed in the vicinity of the focal point or reference point. Lighting. In the projector type headlamp according to any one of claims 1 to 7 ,
A projector-type headlamp, wherein a horizontal length of the projection lens viewed from the optical axis direction is shorter than a vertical length of the projection lens.

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