Patent Description:
Recently, an illumination device having a function of forming a predetermined lighting pattern (a desired projection pattern) on a surface to be illuminated, by means of a high-intensity light source such as a laser, has been practically used. A diffraction optical element such as a hologram has a function of diffracting and emitting an incident light in a desired direction. Thus, by diffracting a light from a light source in a desired direction by means of a diffraction optical element, a predetermined lighting pattern can be formed on a surface to be illuminated.

For example, <CIT> discloses a technique wherein an illumination device having a function of diffracting a light emitted from a laser light source by means of a transmission-type hologram is installed on an automobile, so as to form a predetermined lighting pattern formed of a hologram reconstructed image on a road surface. When information such as a character is recorded in a hologram in advance by using this technique, a reconstructed image such as a character can be displayed as a lighting pattern on a road surface.

<CIT> describes a projecting type image display apparatus including a calculation processing unit for calculating a Fraunhofer diffraction image of an original image, an image display unit for producing/displaying the calculated Fraunhofer diffraction image, and an image converting unit for projecting the produced/displayed Fraunhofer diffraction image to the original image and projecting the original image on the screen. The calculation processing unit has a function of calculating the Fraunhofer diffraction image of the projection image and outputting the same to the image display unit. The image display unit is provided with an image display element on which the Fraunhofer diffraction image is optically displayed. The image projecting unit is provided with first and second lenses for converting the Fraunhofer diffraction image to the original image and projecting the original image on the screen.

<CIT> describes a display device that projects a predetermined projection image on a road surface has: a laser light source that emits a laser beam; and a transmission type hologram that receives the laser light emitted from the laser light source and forms a transmission type hologram on the road surface.

As described above, the illumination device disclosed in <CIT> can project a predetermined lighting pattern on a surface to be illuminated such as a road surface, etc. Upon designing, a designer determines a shape of a lighting pattern, and a position at which the lighting pattern is formed on the surface to be illuminated. Namely, the designer determines in advance a surface to be illuminated which has a predetermined geometric positional relationship with respect to an illumination device, and designs diffraction properties of a diffraction optical element such that a lighting pattern having a predetermined shape is formed at a predetermined position of the surface to be illuminated.

For example, when a hologram is used as a diffraction optical element, interference fringes, which allow a lighting pattern having a predetermined shape to be reconstructed, as a hologram reconstructed image, at a predetermined position of the predetermined surface to be illuminated, are recorded in the hologram. Thus, unless the hologram is replaced, the position of the lighting pattern projected on the surface to be illuminated is unchanged.

Meanwhile, as a new function of the aforementioned illumination device, it is desired that a position of a lighting pattern projected on a road surface or the like can be changed depending on circumstances. To be specific, when a lighting pattern of a direction indicating sign is projected on a road surface in order to show a traveling direction of a vehicle, it is preferable to change a position of the direction indicating sign depending on circumstances.

For example, when the aforementioned illumination device is installed on an automobile, and a direction indicating sign is projected on a road surface from the moving automobile, it is preferable that a projection position is changed such that a display position of the direction indicating sign on the road surface is appropriate, depending on traveling conditions such as a driving speed of the automobile and lane change. However, a conventional illumination device cannot change a projection position of a lighting pattern.

Thus, the object of the present invention is to provide an illumination device which is capable of projecting a predetermined lighting pattern on a surface to be illuminated, such as a road surface, a ground surface, a floor surface, a surface below water, and a wall surface, and is capable of displacing the lighting pattern on the surface to be illuminated.

The above and other objects are achieved by an illumination device as defined in the independent claims, respectively.

According to the illumination device of the present invention, it is possible to project a desired lighting pattern on a surface to be illuminated, such as a road surface, a ground surface, a floor surface, a surface below water, and a wall surface, and further to displace the lighting pattern on the surface to be illuminated.

The present invention is described herebelow based on some illustrated embodiments. In the drawings attached to the specification, a scale size, an aspect ratio and so on are changed and exaggerated from the actual ones, for the convenience of easiness in illustration and understanding. In addition, terms specifying shapes and geometric conditions, e.g., "parallel", "orthogonal", "same", etc. and a value of a length, an angle, etc., are not limited to their strict definitions, but are to be construed to include a range capable of exerting a similar function.

Firstly, a first embodiment (embodiment in which a collimation lens is driven) of the present invention is described with reference to <FIG>.

<FIG> is a perspective view showing an overall structure of an illumination device <NUM> according to the first embodiment of the present invention. The illumination device <NUM> is an illumination device having a function of projecting a predetermined lighting pattern (a desired projection pattern) E on a predetermined surface to be illuminated U.

The surface to be illuminated U is a plane that forms an area to be illuminated by the illumination device <NUM>. In <FIG>, for the sake of convenience, the surface to be illuminated U is drawn as a rectangular area surrounded by dashed lines. In the illustrated example, the lighting pattern E is a V-shaped graphic pattern, but the shape and the size of the lighting pattern E are not limited to those of the illustrated example, and the lighting pattern E may have any optional shape. For example, the lighting pattern E may have a linear shape or a shape of a specific character (this applies to the respective embodiments described later).

For example, the illumination device <NUM> can be used by installing it on a vehicle such as an automobile or an aircraft. When the illumination device <NUM> is used by installing it on a vehicle, information like a traveling direction of the vehicle can be displayed as a lighting pattern E on a surrounding surface to be illuminated such as a road surface, a ground surface, a floor surface, a surface below water, and a wall surface. Described herein is an example in which the illumination device <NUM> is installed on an automobile, and a forward road surface is illuminated such that a lighting pattern E of a direction indicating sign showing its traveling direction (a V-shaped graphic pattern in this illustrated example) is formed. Thus, in the illustrated example, the surface to be illuminated U is set as a road surface in front of the automobile, and the V-shaped lighting pattern E shows a traveling direction of the automobile.

As illustrated, the illumination device <NUM> comprises a light source <NUM>, a magnifying lens <NUM> that broadens a light beam L1 from the light source <NUM> so as to generate a divergent light L2, a collimation lens <NUM> that shapes a light from the light source <NUM> (the divergent light L2 generated by the magnifying lens <NUM>) so as to generate a parallel illumination light L3, a diffraction optical element <NUM> that diffracts the parallel illumination light L3 so as to project a lighting pattern E on a surface to be illuminated U (in this example, on a forward road surface), and a collimation-lens drive unit <NUM> that supports the collimation lens <NUM> and drives the same.

Although illustration of a specific structure is omitted, the illumination device <NUM> further comprises a device housing <NUM>. The device housing <NUM> is a housing that accommodates the light source <NUM>, the magnifying lens <NUM>, the collimation lens <NUM>, the diffraction optical element <NUM> and the collimation-lens drive unit <NUM>. In the illustrated example, the device housing <NUM> is installed on a front part of the automobile. The device housing <NUM> also has a function of fixedly supporting the light source <NUM>, the magnifying lens <NUM>, the diffraction optical element <NUM> and the collimation-lens drive unit <NUM>.

In <FIG>, in order to clearly show the fixedly supporting function, discrete parts of the device housing <NUM> are shown by using ground symbols of an electric circuit. Specifically, in <FIG>, lines extending downward from the light source <NUM>, the magnifying lens <NUM>, the diffraction optical element <NUM> and the collimation-lens drive unit <NUM> and ground symbols <NUM> shown on lower ends of the lines show that these respective constituent elements are fixedly supported by the device housing <NUM>. The collimation lens <NUM> is supported by the collimation-lens drive unit <NUM> so as to be movable with respect to the device housing <NUM>. A driving method of the collimation lens <NUM> by the collimation-lens drive unit <NUM> is described in detail in the following §<NUM>.

Herein, for the convenience of describing a geometric positional relationship among the respective constituent elements that constitute the illumination device <NUM>, an XYZ three-dimensional orthogonal coordinate system having an X axis, a Y axis and a Z axis that are orthogonal to one another is defined as shown in the drawings. In the illustrated example, the illumination device <NUM> is installed on the automobile such that its traveling direction corresponds to a positive X direction, and the surface to be illuminated U (forward road surface) is defined on a plane parallel to an XY plane. In order to illuminate the surface to be illuminated U, the light source <NUM> has a function of emitting an illumination light beam L1 in the positive X direction. The collimation lens <NUM> and the diffraction optical element <NUM> are disposed on planes parallel to a YZ plane.

In this example, a laser light source is used as the light source <NUM>. A laser light (beam) emitted from the laser light source <NUM> is excellent in travelling straight and thus is suited as a light for illuminating the surface to be illuminated U to form the fine lighting pattern E.

As illustrated, the laser beam L1 generated by the light source <NUM> is broadened by the magnifying lens <NUM> so that the divergent light L2 is generated. The magnifying lens <NUM> refracts the layer beam L1 so as to diverge the laser beam L1 into a divergent luminous flux, such that an area occupied by the light spreads in a cross-section orthogonal to the optical axis of the laser beam L1. In other words, the magnifying lens <NUM> shapes a three-dimensional shape of a luminous flux of the laser beam L1. In the example shown here, the laser beam L1 is a luminous flux having a circular section. The divergent light L2 of a conically spreading luminous flux is emergent from the magnifying lens <NUM>. In <FIG>, an optical axis C (an optical axis of the light L2 incident on the collimation lens <NUM>) of the divergent light L2 is drawn with one-dot chain lines. The optical axis C is an axis parallel to the X axis.

The collimation lens <NUM> shapes the three-dimensional shape of the conically spreading divergent light L2 so as to generate a parallel illumination light L3 of a parallel luminous flux, and applies the parallel illumination light L3 to an incident plane Q of the diffraction optical element <NUM>. In the illustrated example, the respective constituent elements are disposed such that the optical axis of the laser beam L1 passes a center point of the magnifying lens <NUM>, that the optical axis C of the divergent light L2 (a center axis of the conically spreading divergent luminous flux) passes a center point of the collimation lens <NUM>, and that an optical axis of the parallel illumination light L3 (a center axis of the parallel luminous flux) passes a center point of the diffraction optical element <NUM>. In this patent application, "an optical axis of a certain light" means "a direction axis along an optical path that follows the center of an area through which the light passes".

Thus, in the illustrated example, the optical axis of the laser beam L1, the optical axis C of the divergent light L2 and the optical axis of the parallel illumination light L3 coincide with one another. These axes are axes parallel to the X axis. Herein, this state is referred to as "standard state". In the standard state, the parallel illumination light L3 forms a parallel luminous flux parallel to the X axis, and has a circular section (a section orthogonal to the optical axis). The diffraction optical element <NUM> is disposed such that its incident plane Q is parallel to the YZ plane. Thus, in the standard state, the parallel illumination light L3 is incident perpendicularly on the incident plane Q of the diffraction optical element <NUM>. As a result, as indicated by broken lines, a circular irradiation area A is formed on the incident plane Q.

However, as described below, when the collimation lens <NUM> is driven by the collimation-lens drive unit <NUM> to deviate from the standard state, the optical axis of the parallel illumination light L3 does not coincide with the optical axis C of the divergent light L2 (the optical axis of the light incident on the collimation lens <NUM>), and an incident angle of the parallel illumination light L3 with respect to the incident plane Q is changed. In this case, the irradiation area A on the diffraction optical element <NUM> has not a precisely circular shape but a slightly deformed elliptic shape.

Next, a function of the diffraction optical element <NUM> is described. The diffraction optical element <NUM> has a function of diffracting the parallel illumination light L3, which has been shaped by the collimation lens <NUM> and has been incident on the incident plane Q, so as to generate a diffracted light L4, and projecting a lighting pattern E on a surface to be illuminated U by the thus obtained diffracted light L4. By causing the parallel illumination light L3 to be incident on the incident plane Q of the diffraction optical element <NUM> from a certain direction (a perpendicular direction in the standard state), the incident light is diffracted in a desired direction so that the lighting pattern E can be formed at a predetermined position by the diffracted light L4.

In the example shown here, the diffraction optical element <NUM> is formed of a hologram recording medium that records interference fringes corresponding to a center wavelength of the laser beam L1 emitted from the laser light source <NUM>, and is disposed parallel to the YZ plane. The hologram recording medium records interference fringes for generating a reconstructed image serving as a predetermined lighting pattern E (a V-shaped graphic pattern) on a surface to be illuminated U (on a forward road surface). By variously adjusting an interference fringe pattern to be recorded, a traveling direction of the diffracted light L4 that is diffracted by the diffraction optical element <NUM> can be controlled, whereby the predetermined lighting pattern E can be formed.

A geometric positional relationship between the diffraction optical element <NUM> and the surface to be illuminated U depends on a position on which the device housing <NUM> is installed on the automobile and a position at which the lighting pattern E is designed to be projected. For example, suppose that the device housing <NUM> is installed to face a traveling direction on a front grill of the automobile at a height position of <NUM> from the road surface, and that the lighting pattern E is designed to be projected on the road surface at a <NUM> position ahead of the automobile. In this case, since a geometric positional relationship between the diffraction optical element <NUM> and the surface to be illuminated U can be defined based on the design information, interference fringes enabling that the predetermined lighting pattern E can be obtained as a reconstructed image on the surface to be illuminated U having such a geometric positional relationship is recoded in the diffraction optical element <NUM>. Thus, the surface to be illuminated U is illuminated with the diffracted light from the diffraction optical element <NUM>, and the lighting pattern E is formed as the illumination pattern on the road surface.

For example, the diffraction optical element <NUM> can be produced by using, as an object light, a scattered light from an actual scattering plate (diffuse plate). To be specific, when a hologram photosensitive material, which is a matrix of the diffraction optical element <NUM>, is irradiated with an object light and a reference light which are coherent light interfering with each other, interference fringes by interference of the lights are formed in the hologram photosensitive material, so that the diffraction optical element <NUM> is produced. As an object light, a scattered light scattered by an economically available isotropic scattering plate can be used, and as a reference light, laser light which is coherent light can be used, for example.

For example, when the lighting pattern E of the V-shaped graphic pattern shown in <FIG> is generated as a reconstructed image, an actual isotropic scattering plate having a shape of the V-shape is prepared, and interference fringes are recorded by irradiating a hologram photosensitive material with a light as an object light which is obtained when the isotropic scattering plate is irradiated with the laser beam, and a laser light having the same wavelength as a reference light.

By using the hologram recording medium recording the interference fringes as the diffraction optical element <NUM>, and by projecting a laser light toward the diffraction optical element <NUM> such that the laser light travels conversely to an optical path of the reference light used upon recording, a reconstructed image of the scattering plate is generated at a position on which the scattering plate, which originated the object light used when the diffraction optical element <NUM> was produced, is located. When the scattering plate, which originated the object light used when the diffraction optical element <NUM> was produced, has uniform planar scattering properties, the reconstructed image of the scattering plate, which is generated by the diffraction optical element <NUM>, is also a uniform planar illumination area. This area, in which the reconstructed image of the scattering plate is generated, can be the lighting pattern E.

Instead of being formed by using a real object light and a real reference light, a complicated interference fringe pattern formed on each diffraction optical element <NUM> can be designed by using a computer based on a wavelength and an incident direction of expected illumination light for reconstruction as well as a shape and a position of an image to be reconstructed. The diffraction optical element <NUM> thus obtained is also referred to as computer generated hologram (CGH). For example, as in the aforementioned example, when it is designed that the lighting pattern E is projected on a road surface at an <NUM> position ahead of the automobile, it is necessary to perform a recording with an object light from a scattering plate as far as <NUM>, which is practically of great difficulty. In this case, a computer generated hologram is preferably used as the diffraction optical element <NUM>.

When a computer generated hologram is used, for example, a Fourier conversion hologram in which respective points on each diffraction optical element <NUM> have the same diffusion angle properties may be generated by a computer. Further, an optical member such as a lens may be disposed on the downstream side of the diffraction optical element <NUM>, in order that the overall area of the lighting pattern E is illuminated with the entire diffracted light L4 from the diffraction optical element <NUM>.

Specifically, the diffraction optical element <NUM> may be a volume type hologram recording medium using a photopolymer, a volume type hologram recording medium that uses a photosensitive medium containing a silver salt material for recording, or a relief type (emboss type) hologram recording medium. A relief type hologram may be made of materials such as resin, glass, metal and organic/inorganic hybrid material. In addition, the diffraction optical element <NUM> may be of a transmission type or of a reflection type. In the illustrated example, a transmission type diffraction optical element <NUM> is used. On the other hand, when a reflection type diffraction optical element <NUM> is used, the light source <NUM> has to be disposed on the opposite side of the diffraction optical element <NUM>.

A luminous flux emergent from such a diffraction optical element <NUM> has an outline corresponding to the pattern recorded in the diffraction optical element <NUM>. Thus, the lighting pattern E having an outline corresponding to the interference fringes recorded in the diffraction optical element <NUM> is formed on the surface to be illuminated U that is illuminated with such a luminous flux.

In the illumination device <NUM> shown in <FIG>, the light source <NUM> generates a light beam L1 having an optical axis parallel to the X axis, the magnifying lens <NUM> generates a divergent light L2 which diverges about the optical axis of the light beam L1 as a central axis, and the collimation lens <NUM> shapes the divergent light L2 so as to generate a parallel illumination light L3 and applies the parallel illumination light L3 to the diffraction optical element <NUM> having the incident plane Q parallel to the YZ plane. Moreover, the collimation lens <NUM> can be translated by the collimation-lens drive unit <NUM> along a movement plane P that is orthogonal to the optical axis C of the incident divergent light L2. Herein, the "translation" means that respective points constituting the collimation lens <NUM> are moved in the same direction by the same distance, without any rotating factor.

The feature of the present invention is to add, to the illumination device having a function of projecting a predetermined lighting pattern E on a predetermined surface to be illuminated U, a function of changing a projection position of the lighting pattern E.

For example, in the illustrated example, the illumination device is installed on an automobile. When a direction indicating sign is projected on a road surface from a moving automobile, it is convenient that a projection position can be changed such that a display position of the direction indicating sign on the road surface is appropriate depending on driving conditions of the automobile such as a driving speed of the automobile and lane change. The illustrated illumination device <NUM> has such a function of changing a projection position.

An important feature of the illumination device <NUM> according to the first embodiment is that the collimation lens <NUM> is driven by the collimation-lens drive unit <NUM>. As described above, the light source <NUM>, the magnifying lens <NUM>, the diffraction optical element <NUM> and the collimation-lens drive unit <NUM> are all fixedly supported by the device housing <NUM>. On the other hand, the collimation lens <NUM> is not directly fixed on the device housing <NUM> but is supported by the collimation-lens drive unit <NUM> so as to be movable.

Namely, a relative position between the collimation lens <NUM> and the device housing <NUM> is changed by the collimation-lens drive unit <NUM>. This means that a relative position of the collimation lens <NUM> with respect to the light source <NUM>, the magnifying lens <NUM> and the diffraction optical element <NUM> is also changed.

To be specific, the collimation-lens drive unit <NUM> has a function of translating the collimation lens <NUM> along the movement plane P (shown by two-dot chain lines in <FIG>) that is orthogonal to the optical axis C of the light incident on the collimation lens <NUM> (an optical axis of the divergent light L2). In the illustrated example, since the optical axis C of the divergent light L2 is parallel to the X axis, the movement plate P is a plane parallel to the YZ plane.

In the example shown here, when a direction orthogonal to the surface to be illuminated U (the Z-axis direction) is referred to as a vertical direction d1, and a direction parallel to the surface to be illuminated U (a direction along the XY plane) is referred to as a horizontal direction d2, as shown by the arrows d1 and d2 in <FIG>, the collimation-lens drive unit <NUM> has a vertically driving function of moving the collimation lens <NUM> along the movement plane P in the vertical direction d1, and a horizontally driving function of moving the collimation lens <NUM> along the movement plane P in the horizontal direction d2. By combining the vertically driving function and the horizontally driving function, the collimation lens <NUM> can be translated along the movement plane P, not only in the vertical direction d1 and the horizontal direction d2 but also in a given direction.

As illustrated, the collimation-lens drive unit <NUM> has a drive mechanism <NUM> and a support arm <NUM>, and has a function of supporting the collimation lens <NUM> and translating the collimation lens <NUM> along the movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis C of a light incident on the collimation lens <NUM>. As such a drive mechanism <NUM>, a general mechanism for moving the support arm <NUM> with the use of a motor and gears can be employed, and detailed description thereof is omitted here.

The noteworthy thing here is that, when the collimation-lens drive unit <NUM> drives the collimation lens <NUM> such that the collimation lens <NUM> is translated along the movement plane P parallel to the YZ plane, an incident direction of the parallel illumination light L3 with respect to the incident plane Q is changed by the driving operation. Namely, in the standard state shown in <FIG>, the parallel illumination light L3 is incident on the incident plane Q in a direction perpendicular thereto. However, when the collimation lens <NUM> is translated along the movement plane P, an incident direction of the parallel illumination light L3 with respect to the incident plane Q is changed in accordance with the direction of motion of the collimation lens <NUM> and the distance moved by the collimation lens <NUM>, so that an emergent direction of the diffracted light L4 emergent from the diffraction optical element <NUM> is also changed. As a result, a projection position of the lighting pattern E on the surface to be illuminated U is also changed.

In other words, when the collimation lens <NUM> is moved, a light incident position of the light with respect to the collimation lens <NUM> is changed. In accordance with the displacement direction and the displacement quantity of the incident position, an emergent angle of the parallel illumination light L3 emergent from the collimation lens <NUM> is changed. Thus, an incident angle of the parallel light source L3 with respect to the diffraction optical element <NUM> is changed, so that an emergent direction of the diffracted light L4 emergent from the diffraction optical element <NUM> is changed, whereby a projection position of the lighting pattern E on the surface to be illuminated U is changed. In conclusion, in the first embodiment shown here, by changing a relative positional relationship between the light source <NUM> and the collimation lens <NUM>, an incident angle of the parallel illumination light L3 with respect to the diffraction optical element <NUM> is changed.

<FIG> is a top view of the illumination device <NUM> shown in <FIG> (illustration of some constituent elements is omitted). As indicated by solid lines in <FIG>, the laser beam L1 emitted from the light source <NUM> in the positive X direction is broadened by the magnifying lens <NUM> into the divergent light L2 having the optical axis C. The divergent light L2 is shaped by the collimation lens <NUM> into the parallel illumination light L3. The parallel illumination light L3 is incident on the incident plane Q of the diffraction optical element <NUM>, and is emergent as the diffracted light L4 onto the surface to be illuminated U. As illustrated, the optical axis C of the divergent light L2 is orthogonal to the movement plane P of the collimation lens <NUM>.

In <FIG>, a line group L30 drawn on the right side of the collimation lens <NUM> shows an optical axis of the parallel illumination light L3, an arrow group L31 shows an optical path of a light beam on one of profile positions (an upper end position in <FIG>) of luminous fluxes constituting the parallel illumination light L3, and an arrow group L32 shows an optical path of a light beam on the other profile position (a lower end position in <FIG>) of the luminous fluxes constituting the parallel illumination light L3.

As illustrated, a profile line group of the collimation lens <NUM>, the straight line group L30, and the arrow groups L31 and L32 are composed of three kinds of lines, namely, solid lines, broken lines and one-dot chain lines. The solid lines show a case in which the collimation lens <NUM> is positioned in the standard state. The broken lines show a case in which the collimation lens <NUM> is translated upward in <FIG> (positive Y direction). The one-dot chain lines show a case in which the collimation lens <NUM> is translated downward in <FIG> (negative Y direction). Herebelow, for the sake of convenience, when these three kinds of lines should be discriminated, the terms (solid line), (broken line) and (one-dot chain line) are affixed to a reference numeral. For example, an arrow drawn with the broken lines in the arrow group L31 is referred to as "arrow L31 (broken line)".

Similarly, an arrow group drawn on the right side of the diffraction optical element <NUM> shows an optical path of the diffracted light L4 from the diffraction optical element <NUM>, which is composed of solid lines, broken lines and one-dot chain lines. Also, the solid lines show a case in which the collimation lens <NUM> is positioned in the standard state. The broken lines show a case in which the collimation lens <NUM> is translated upward in <FIG> (positive Y direction). The one-dot chain lines show a case in which the collimation lens <NUM> is translated downward in <FIG> (negative Y direction). Herebelow, for the sake of convenience, when these three kinds of lines should be discriminated, the terms (solid line), (broken line) and (one-dot chain line) are affixed to the reference numeral L4. For example, of the diffracted light L4, the diffracted light shown by an arrow drawn with the broken lines is referred to as "diffracted light L4 (broken line)".

As described above, the solid lines in <FIG> show the standard state. In the standard state, the optical axis of the laser beam L1, the optical axis C of the divergent light L2 and the optical axis of the parallel illumination light L3 are positioned on the same line. Namely, in the standard state, the optical axis of the laser beam L1 passes the center point of the magnifying lens <NUM>, the optical axis C of the divergent light L2 passes the center point of the collimation lens <NUM>, and the optical axis of the parallel illumination light L3 passes the center point of the diffraction optical element <NUM>. Parallel luminous fluxes within a range between the arrow L31 (solid line) and the arrow L32 (solid line) are emergent as the parallel illumination light L3 from the collimation lens <NUM> and are incident on the incident plane Q of the diffraction optical element <NUM> in a direction perpendicular thereto. In this case, the irradiation area A formed in the incident plane Q is a circular area as shown by the broken lines in <FIG>. The diffracted light L4 (solid line) is emergent from the diffraction optical element <NUM>, so that the lighting pattern E is projected at a standard position on the surface to be illuminated U.

On the other hand, as shown by the broken lines in <FIG>, when the collimation lens <NUM> is translated along the movement plane P upward in <FIG> (positive Y direction), the position of the optical axis C of the divergent light L2 from the magnifying lens <NUM> is unchanged, but a relative position of the collimation lens <NUM> with respect to the optical axis C is changed. Thus, an incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed in accordance with the direction of motion and the movement quantity of the collimation lens <NUM>. Thus, an emergent angle of the parallel illumination light L3 emergent from the collimation lens <NUM> is changed in accordance with the incident position of the divergent light L2. Parallel luminous fluxes within a range between the arrow L31 (broken line) and the arrow L32 (broken line) are emergent as the parallel illumination light L3 (broken line) from the collimation lens <NUM>. Although the parallel illumination light L3 (broken line) is composed of parallel luminous fluxes of light beams parallel to each other, the parallel illumination light L3 is inclined to the optical axis C of the divergent light L2 and is not parallel to the X axis.

Thus, an incident angle of the parallel illumination light L3 (broken line) with respect to the incident plane Q of the diffraction optical element <NUM> differs from the incident angle in the aforementioned standard state. In addition, the irradiation area A formed in the incident plane Q is not of a precisely circular shape but of a slightly deformed elliptic shape. In addition, a formation position thereof is slightly shifted from the position in the standard state. Namely, since the incident angle of the parallel illumination light L3 is changed, the diffracted light L4 (broken line), which is oriented in a direction different from that of the diffracted light L4 (solid line), is emergent from the diffraction optical element <NUM>, whereby the lighting pattern E is projected on the surface to be illuminated U at a position which is different from the standard position (in the illustrated example, a position displaced in the positive Y direction from the standard position).

On the other hand, as shown by the one-dot chain lines in <FIG>, when the collimation lens <NUM> is translated along the movement plane P downward in <FIG> (negative Y direction), the position of the optical axis C of the divergent light L2 from the magnifying lens <NUM> is unchanged, but a relative position of the collimation lens <NUM> with respect to the optical axis C is changed. Thus, an incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed in accordance with the direction of motion and the movement quantity of the collimation lens <NUM>. Thus, an emergent angle of the parallel illumination light L3 emergent from the collimation lens <NUM> is changed in accordance with the incident position of the divergent light L2. Parallel luminous fluxes within a range between the arrow L31 (one-dot chain line) and the arrow L32 (one-dot chain line) are emergent as the parallel illumination light L3 (one-dot chain line) from the collimation lens <NUM>. Although the parallel illumination light L3 (one-dot chain line) is composed of parallel luminous fluxes of light beams parallel to each other, the parallel illumination light L3 is inclined to the optical axis C of the divergent light L2 and is not parallel to the X axis.

Thus, an incident angle of the parallel illumination light L3 (one-dot chain line) on the incident plane Q of the diffraction optical element <NUM> differs from the incident angle in the aforementioned standard state. Of course, the incident angle also differs from the incident angle of the parallel illumination light L3 (broken line). The irradiation area A formed in the incident plane Q has also an elliptic shape, and a formation position thereof is also slightly shifted from the position in the standard state. Namely, since the incident angle of the parallel illumination light L3 is changed, the diffracted light L4 (one-dot chain line), which is oriented in a direction different from those of the diffracted light L4 (solid line) and the diffracted light L4 (broken line), is emergent from the diffraction optical element <NUM>, whereby the lighting pattern E is projected on the surface to be illuminated U at a position which is different from the standard position (in the illustrated example, a position displaced in the negative Y direction from the standard position).

In the case of the illumination device <NUM> shown in <FIG>, when the collimation lens <NUM> is translated along the movement plane P in the horizontal direction d2 (a direction parallel to the Y axis) by the collimation-lens drive unit <NUM>, the lighting pattern E projected on the surface to be illuminated U is displaced in the right and left direction (a direction parallel to the Y axis) seen from the automobile.

On the other hand, in the illumination device <NUM> shown in <FIG>, when the collimation lens <NUM> is translated along the movement plane P in the vertical direction d1 (a direction parallel to the Z axis), the lighting pattern E projected on the surface to be illuminated U is displaced in the traveling direction (a direction parallel to the X axis) seen from the automobile. The reason why such a displacement occurs can be easily understood in consideration that, in the side view of the illumination device <NUM> shown in <FIG>, the Y axis of the top view of <FIG> is replaced with the Z axis.

Namely, in consideration of the side view in which the Y axis in <FIG> is replaced with the Z axis, the solid lines show the case in which the collimation lens <NUM> is arranged in its position in the standard state, the broken lines show the case in which the collimation lens <NUM> is translated vertically upward (positive Z direction), and the one-dot chain lines show the case in which the collimation lens <NUM> is translated vertically downward (negative Z direction). As shown in <FIG>, when the lighting pattern E is formed on the surface to be illuminated U in the forward road surface by the illumination device <NUM> installed on the automobile, the orientation of the diffracted light L4 in <FIG> as the side view needs to be amended slightly downward.

As indicated by the broken lines in the side view, when the collimation lens <NUM> is translated along the movement plane P vertically upward (positive Z direction), the diffracted light L4 (broken line) is emerged from slightly above the diffracted light L4 (solid line), so that the lighting pattern E is projected on the surface to be illuminated U at a position farther than the position of the lighting pattern E in the standard position (a position displaced in the positive X direction from the standard position). Similarly, when the collimation lens <NUM> is translated along the movement plane P vertically downward (negative Z direction), the diffracted light L4 (one-dot chain line) is emerged from slightly below the diffracted light L4 (solid line), so that the lighting pattern E is projected on the surface to be illuminated U at a position closer than the position of the lighting pattern E in the standard position (a position displaced in the positive X direction from the standard position).

To sum up, in the illumination device <NUM> shown in <FIG>, when the collimation lens <NUM> is translated by the collimation-lens drive unit <NUM> along the movement plane P in the vertical direction d1 (a direction parallel to the Z axis), the lighting pattern E projected on the surface to be illuminated U is displaced in the traveling direction of the automobile (a direction parallel to the X axis).

<FIG> is a plan view for describing a displacement state of the lighting pattern E projected by the illumination device <NUM> shown in <FIG> on the surface to be illuminated U. A lighting pattern E0 shown by the solid lines in <FIG> shows a pattern projected on the surface to be illuminated U in the standard state. In this standard state, when the collimation lens <NUM> is translated along the movement plane P vertically upward (positive Z direction), as described above, the lighting pattern E0 is displaced to a farther position seen from the automobile, so that a lighting pattern E1 shown by the solid lines in <FIG> is obtained.

On the other hand, in the standard state, when the collimation lens <NUM> is translated along the movement plane P vertically upward (positive Z direction) and is translated horizontally leftward (positive Y direction), the lighting pattern E0 is displaced, on the surface to be illuminated U, to a farther and leftward position seen from the automobile, so that a lighting pattern E2 shown by the broken lines in <FIG> is obtained. Similarly, in the standard state, when the collimation lens <NUM> is translated along the movement plane P vertically upward (positive Z direction) and is translated horizontally rightward (negative Y direction), the lighting pattern E0 is displaced, on the surface to be illuminated U, to a farther and rightward position seen from the automobile, so that a lighting pattern E3 shown by the one-dot chain lines in <FIG> is obtained.

As described above, the collimation-lens drive unit <NUM> in the illumination device <NUM> shown in <FIG> has the vertically driving function of moving the collimation lens <NUM> along the movement plane P in the vertical direction d1, and the horizontally driving function of moving the collimation lens <NUM> along the movement plane P in the horizontal direction d2, as shown by the arrows d1 and d2 in <FIG>. Thus, by combining the vertically driving function and the horizontally driving function, the collimation lens <NUM> can be translated along the movement plane P, not only in the vertical direction d1 and the horizontal direction d2 but also in a given direction.

As a result, an incident angle of the parallel illumination light L3 with respect to the diffraction optical element <NUM> is changed, so that an emergent angle of the diffracted light L4 emergent from the diffraction optical element <NUM> can be changed, whereby the lighting pattern E can be moved to a given position on the surface to be illuminated U. <FIG> shows that the lighting pattern E0 in the standard state is displaced to the lighting patterns E1 to E3 at distant positions from the illumination device <NUM>. However, it goes without saying that the lighting pattern E0 can be displaced to a position closer to the illumination device <NUM>. In particular, when a distant area is illuminated by the illumination device <NUM>, a formation position of the lighting pattern E can be significantly displaced only by moving slightly the collimation lens <NUM>.

When the lighting pattern E is displaced from its position in the standard state, a profile, in particular, an outline of a luminous flux of the diffracted light L4 from the diffraction optical element <NUM> is slightly changed, so that the lighting pattern E (the V-shaped graphic pattern) displayed on the surface to be illuminated U is slightly deformed in a precise sense. However, as long as the displacement quantity of the collimation lens <NUM> is not extremely large, the deformation of the lighting pattern E is negligible and no serious trouble practically occurs.

In addition, in the example shown in <FIG>, in a case where the outline of the irradiation area A in the standard state is designed to reach a point close to the outline of the incident plane Q of the diffraction optical element <NUM>, when the collimation lens <NUM> is translated along the movement plane P, a part of the irradiation area A protrudes from the incident plane Q. Specifically, in the case shown in <FIG>, a part of the outline of the irradiation area A shown by the circle in the broken lines protrudes outside from the diffraction optical element <NUM>. However, even if such a protrusion occurs, no serious problem occurs. This is because, since the diffraction optical element <NUM> records hologram interference fringes, even if the illumination light for reconstruction is applied to only a part of the diffraction optical element <NUM>, the lighting pattern E is formed as a hologram reconstructed image. In this case, a protruding light is preferably cut by an aperture.

Of course, when a part of the parallel illumination light L3 protrudes from the hologram recording area, a quantity of light for illumination decreases, so that an irradiance of the lighting pattern E formed as a hologram reconstructed image decreases. In order to prevent decrease in irradiance, the size of the diffraction optical element <NUM> is designed slightly larger, such that the irradiation area A does not protrude from the hologram forming surface on the incident plane Q, even when the position of the irradiation area A formed on the incident plane Q of the diffraction optical element <NUM> is changed by the movement of the collimation lens <NUM>.

However, when the size of the diffraction optical element <NUM> is designed to be larger for preventing protrusion, another problem occurs: the size of the illumination device <NUM> becomes larger as a whole. Thus, in terms of reduction in size of the device, as in the example shown in <FIG>, it is preferable that the outline of the irradiation area A in the standard state is designed to reach a point close to the outline of the incident plane Q of the diffraction optical element <NUM>, and that some protrusion of the irradiation area A is allowed.

Such a protrusion similarly occurs in the collimation lens <NUM>. Namely, in <FIG>, when the outline of the irradiation area of the conically spreading divergent light L2 with respect to the collimation lens <NUM> is designed to reach a point close to the outline of the collimation lens <NUM>, there is a possibility that a part of the divergent light L2 protrudes outside from the collimation lens <NUM> by the movement of the collimation lens <NUM>.

Even when such a protrusion occurs, no serious trouble occurs, although a quantity of light for illumination decreases and an irradiance of the lighting pattern E lowers (a protruding light is preferably cut by an aperture). When a size of the collimation lens <NUM> is designed to be larger, such a protrusion can be of course prevented. However, another problem occurs: the size of the illumination device <NUM> becomes larger as a whole.

Next, some modification examples of the illumination device <NUM> according to the first embodiment shown in <FIG> are described.

<FIG> is a perspective view showing an overall structure of an illumination device 100RGB according to a modification example of the first embodiment shown in <FIG>. Similarly to <FIG>, an XYZ three-dimensional orthogonal coordinate system is defined. A feature of the illumination device 100RGB is that it comprises three light sources 110R, <NUM> and 110B, three magnifying lenses 120R, <NUM> and 120B and three collimation lenses 130R, <NUM> and 130B, which are respectively disposed correspondingly to the three light sources. The respective three sets of those constituent elements are arranged side by side in the horizontal direction (Y-axis direction). In order to receive parallel illumination lights L3R, L3G and L3B from the respective collimation lenses 130R, <NUM> and 130B, the diffraction optical element 140RGB has a horizontally elongated shape.

The three light sources 110R, <NUM> and 110B are laser light sources that are basically similar to the light source <NUM> shown in <FIG>, but have functions of generating lights of different wavelengths. To be specific, the light source 110R is a red laser light source that generates a red laser beam L1R, the light source <NUM> is a green laser light source that generates a green laser beam L1G, and the light source 110B is a blue laser light source that generates blue laser beam L1B. They emit the respective laser beams L1R, L1G and L1B in a direction parallel to the X axis. These light sources may either be provided as independent components, or be a light emission module in which the light sources are arranged on a common substrate.

The three magnifying lens 120R, <NUM> and 120B and the three collimation lens 130R, <NUM> and 130B are totally the same constituent elements as the magnifying lens <NUM> and the collimation lens <NUM> shown in <FIG>. Thus, the red laser beam L1R generated by the red light source 110R is broadened by the magnifying lens 120R into a red divergent light L2R. The red divergent light L2R is further shaped by the collimation lens 130R into a red parallel illumination light L3R. The red parallel illumination light L3R is applied to a corresponding incident area AR (in the illustrated example, a circular area shown by broken lines) on an incident plane Q of the diffraction optical element 140RGB.

Similarly, a green laser beam L1G generated by the green light source <NUM> is broadened by the magnifying lens <NUM> into a green divergent light L2G. The green divergent light L2G is further shaped by the collimation lens <NUM> into a green parallel illumination light L3G. The green parallel illumination light L3G is applied to a corresponding incident area AG (in the illustrated example, a circular area shown by broken lines) on the incident plane Q of the diffraction optical element 140RGB. In addition, a blue laser beam L1B generated by the blue light source 110B is broadened by the magnifying lens 120B into a blue divergent light L2B. The blue divergent light L2B is further shaped by the collimation lens 130B into a blue parallel illumination light L3B. The blue parallel illumination light L3B is applied to a corresponding incident area AB (in the illustrated example, a circular area shown by broken lines) on the incident plane Q of the diffraction optical element 140RGB.

Similarly to the illumination device <NUM> shown in <FIG>, in the standard state, an optical axis of the laser beam L1R, L1G, L1B, an optical axis CR, CG, CB of the divergent light L2R, L2G, L2B, and an optical axis of the parallel illumination light L3R, L3G and L3B are parallel to the X axis. However, when the collimation lens 130R, <NUM>, 130B is translated, the optical axis of the parallel illumination light L3R, L3G, L3B of each color is inclined to the X axis, and a shape and a formation position of the corresponding incident area AR, AG, AB of each color are slightly changed.

Similarly to the diffraction optical element <NUM> shown in <FIG>, the diffraction optical element 140RGB has the incident plane Q parallel to the YZ plane, and has a function of diffracting the parallel illumination light L3R, L3G, L3B of each color into a diffracted light L4RGB and projecting a lighting pattern E on a surface to be illuminated U by the obtained diffracted light L4RGB. In the example shown here, a hologram interference fringe pattern, which records interference fringes corresponding to a center wavelength of the red laser beam L1R, is recorded in and near the red corresponding irradiation area AR in the incident plane Q of the diffraction optical element 140RGB. A hologram interference fringe pattern, which records interference fringes corresponding to a center wavelength of the green laser beam L1G, is recorded in and near the green corresponding irradiation area AG. A hologram interference fringe, which records interference fringes corresponding to a center wavelength of the blue laser beam L1B, is recorded in and near the blue corresponding irradiation area AB.

These hologram interference fringes are interference fringes for generating a reconstructed image as a predetermined lighting pattern E (V-shaped graphic pattern) on the surface to be illuminated U parallel to the XY plane. Thus, a red diffracted light from the red corresponding irradiation area AR, a green diffracted light from the green corresponding irradiation area AG and a blue diffracted light from the blue corresponding irradiation area AB all form a reconstructed image as the lighting pattern E at the same position on the surface to be illuminated U.

As a result, the lighting pattern E is a colored V-shaped graphic pattern formed by superimposing diffracted lights of three colors. A method of manufacturing the diffraction optical element 140RGB having hologram interference fringes for reconstructing such an image as above is the same as the method of manufacturing the diffraction optical element <NUM> shown in <FIG>, and detailed description thereof is omitted here.

The three laser light sources 110R, <NUM> and 110B may have radiant fluxes different from one another. By adjusting the radiant fluxes [unit: W] of the three laser light sources 110R, <NUM> and 110B, a color of the lighting pattern E can be adjusted. In addition, in order to increase a light intensity, a plurality of the laser light sources may be provided for each of the emission wavelength ranges. In the illustrated example, the single diffraction optical element 140RGB is used. However, instead thereof, three diffraction optical elements 140R, <NUM> and 140B may be used, and the respective parallel incident lights L3R, L3G and L3B of respective color may be applied to the corresponding diffraction optical elements 140R, <NUM> and 140B. However, when the single diffraction optical element 140RGB is used, the incident plane Q is a continuous area. Thus, it can be restrained that the irradiation area AR, AG, AB formed by the parallel illumination area L3R, L3G, L3B of each color protrudes outside from the diffraction optical element.

The collimation-lens drive unit 150B is a constituent element similar to the collimation-lens drive unit <NUM> shown in <FIG>. Namely, as illustrated, the collimation-lens drive unit 150B has a drive mechanism 151B and a support arm 152B, and has a function of supporting the collimation lens 130B and translating the collimation lens 130B along a movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis CB of the light incident on the collimation lens 130B.

Although not shown in <FIG> in order to avoid complexity, collimation-lens drive units 150R and <NUM>, which have the same structure as that of the collimation-lens drive unit 150B, are also provided. The collimation-lens drive unit 150R has a function of supporting the collimation lens 130R and translating the collimation lens 130R along a movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis CR of the light incident on the collimation lens 130R. Similarly, the collimation-lens drive unit <NUM> has a function of supporting the collimation lens <NUM> and translating the collimation lens <NUM> along a movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis CG of the light incident on the collimation lens <NUM>.

Although illustration of a specific structure is omitted, the illumination device 100RGB further comprises a device housing <NUM>. The device housing <NUM> is a housing that accommodates the three light sources 110R, <NUM> and 110B, the three magnifying lenses 120R, <NUM> and 120B, the three collimation lenses 130R, <NUM> and 130B, the one diffraction optical element 140RGB, and the three collimation-lens drive units 150R, <NUM> and 150B. In the example shown here, the device housing <NUM> is installed at a front part of an automobile. The device housing <NUM> also serves a function of fixedly supporting the three light sources 110R, <NUM> and 110B, the three magnifying lenses 120R, <NUM> and 120B, the one diffraction optical element 140RGB and the three collimation-lens drive units 150R, <NUM> and 150B.

Similarly to <FIG>, in <FIG>, in order to clearly show the fixedly supporting function, the discrete parts of the device housing <NUM> are shown by using ground symbols of an electric circuit. Note that the reference numeral "<NUM>" is omitted for some of the ground symbols, in order to avoid complexity. The constituent elements other than the three collimation lenses 130R, <NUM> and 130B are fixedly supported by the device housing <NUM>. On the other hand, the three collimation lenses 130R, <NUM> and 130B are respectively supported by the collimation-lens drive units 150R, <NUM> and 150B so as to be movable with respect to the device housing <NUM> (translatable along the movement planes P parallel to the YZ plane).

As described above, the illumination device 100RGB according to the modification example has a function of projecting the lighting pattern E as a colored hologram reconstructed image. Thus, by translating the respective collimation lenses 130R, <NUM> and 130B by means of the collimation-lens drive units 150R, <NUM> and 150B in the same direction by the same movement quantity, a projection position of the colored lighting pattern E can be displaced in a desired direction.

It is not necessary that the respective collimation lenses 130R, <NUM> and 130B are moved all together in the same direction by the same movement quantity. They can be moved in different directions by different movement quantities. When the three collimation lenses are moved together, the colored lighting pattern E can be displaced while its shape is maintained, as described above. On the other hand, when the three collimation lenses are separately moved (moved in different directions), a red lighting pattern ER, a green lighting pattern EG and a blue lighting pattern EB (they are all V-shaped graphic pattern) are displaced in different directions, whereby the colored lighting pattern E is decomposed into different colored lighting patterns, and the different colored lighting patterns are separately displayed. However, when such different lighting patterns are desired to be separately displayed, the three collimation lenses may be moved separately.

Thus, it is not necessary that the three collimation lenses are moved all together, one or more of the collimation lens(es) may be not driven but fixed on the device housing <NUM>. For example, in the example shown in <FIG>, as described above, illustration of the collimation-lens drive units 150R and <NUM> is omitted, but the three collimation-lens drive units 150R, <NUM> and 150B are actually provided. However, when this modification example is carried out, it is not necessary that the three collimation-lens drive units 150R, <NUM> and 150B are provided, but at least one collimation-lens drive unit may be provided.

For example, when only the collimation-lens drive unit 150B shown in <FIG> is provided, and the two not-shown collimation-lens drive units 150R and <NUM> are not provided, the collimation lenses 130R and <NUM> are fixed on the device housing <NUM>, and only the collimation lens 130B can be moved. In this case, in the standard state, the colored lighting pattern E is displayed at the position as shown. When the collimation lens 130B is moved, the lighting pattern E is displayed at the same position by red and green mixed color components, and only a blue lighting pattern E is displaced.

In addition, in the modification example shown in <FIG>, the three light sources 110R, <NUM> and 110B are light sources that generate lights of different wavelengths. However, when colored display is not necessary, it is not necessary that the three light sources are light sources that generate lights of different wavelengths. For example, when light sources that generate laser beams of the same wavelength are used as the three light sources 110R, <NUM> and 110B, the lighting pattern E is a monochromatic pattern, but is displayed as a brighter pattern as compared with a case in which a single light source is used. In this case, when the respective collimation lenses 130R, <NUM> and 130B are moved all together, the bright pattern can be displaced as it is. On the other hand, when the respective collimation lenses 130R, <NUM> and 130B are separately moved, the bright pattern is decomposed into three dark patterns.

As described above, when lights of the same wavelength are used, only one laser light source <NUM> may be used. In this case, a laser beam generated by the one laser light source <NUM> is split into three beams by using an optical element such as a beam splitter, and the three beams are supplied to the respective magnifying lenses 120R, <NUM> and 120B, and the respective collimation lenses 130R, <NUM> and 130B.

In addition, although <FIG> shows the example in which the lights generated by the three light sources 110R, <NUM> and 110B are supplied to the three collimation lenses 130R, <NUM> and 130B, the number of the light sources and the number of the collimation lenses are not necessarily limited to three, but the number may be a given number n.

In the modification example described here, a plurality of light sources the number of which is n are provided, and a plurality of collimation lenses the number of which is n are provided correspondingly to the respective light sources; wherein each collimation lens shapes a light from the corresponding light source into a parallel illumination light and applies the parallel illumination light to a predetermined corresponding irradiation area of the diffraction optical element; wherein each corresponding irradiation area diffracts the applied parallel illumination light so as to project a lighting pattern on a surface to be illuminated U; and wherein the collimation-lens drive unit may translate at least one of the n collimation lenses.

(<NUM>) Modification Example (not covered by the claims): omission of magnifying lens.

In the illumination device <NUM> shown in <FIG>, the magnifying lens <NUM> is disposed between the light source <NUM> and the collimation lens <NUM>, a light beam L1 generated by the light source <NUM> is broadened by the magnifying lens <NUM> so as to generate a divergent light L2, and the divergent light L2 is given to the collimation lens <NUM>. However, when the light source <NUM> has a function of generating a light having a sectional area sufficient for displaying the lighting pattern E, the magnifying lens <NUM> can be omitted because such a light is not needed to be broadened.

Namely, when an emergent light emergent from the light source <NUM> has a sectional area sufficient for displaying the lighting pattern E, the emergent light may be directly supplied to the collimation lens <NUM>, and the collimation lens <NUM> shapes the emergent light so as to generate a parallel illumination light L3. The structure in which the magnifying lens is omitted can be also applied to the illumination device 100RGB shown in <FIG>.

In the aforementioned examples and the modification examples, the collimation-lens drive unit <NUM> translates the collimation lens <NUM> along the movement plane P that is orthogonal to the optical axis C of a light incident on the collimation lens <NUM>. To be more specific, since the optical axis C of the light incident on the collimation lens <NUM> is an axis parallel to the X axis, the collimation lens <NUM> is translated along the movement plate P parallel to the YZ plane.

However, the direction of motion of the collimation lens <NUM> is not limited to a direction along the movement plane P that is orthogonal to the optical axis C of a light incident on the collimation lens <NUM>, and the collimation lens <NUM> may be moved in a given direction. However, when the collimation lens <NUM> is moved in a direction that is "parallel" to the optical axis C of a light incident on the collimation lens <NUM>, the collimation lens <NUM> merely serves a function as a zoom lens, and cannot achieve the object of displacing the lighting pattern E on the surface to be illuminated U.

Thus, the collimation-lens drive unit <NUM> may translate the collimation lens <NUM> in a given direction of motion that is "not parallel" to the optical axis C of a light incident on the collimation lens <NUM>. Note that, as described in §<NUM>, when the collimation lens <NUM> can be moved in the vertical direction d1 and the horizontal direction d2, the lighting pattern E can be displaced in a given direction on the surface to be illuminated U. Thus, it is actually sufficient to employ the structure in which the collimation lens <NUM> is translated along the movement plane P that is orthogonal to the optical axis C of a light incident on the collimation lens <NUM>.

When the above structure is employed, the configuration of the collimation-lens drive unit <NUM> can be simplified, and the illumination device can be reduced in size as a whole. Thus, it is actually preferable to employ the structure in which the collimation lens <NUM> is translated along the movement plane P that is orthogonal to the optical axis C.

In the aforementioned embodiment, the example in which the illumination device according to the present invention is installed on a front grill of an automobile is shown. However, it goes without saying that the utilization of the illumination device according to the present invention is not limited to the example in which the illumination device is installed on a front grill of an automobile. For example, the illumination device can be installed on a lighting unit of a general vehicle including an automobile. Alternatively, the illumination device can be located on a road surface and can be used in a stationary state.

Some modification examples related to the first embodiment of the present invention has been described, but various modification examples are possible in addition thereto.

Next, a second embodiment of the present invention is described with reference to <FIG> and <FIG>. A feature of the first embodiment described in §<NUM> is that a collimation lens is driven. On the other hand, a feature of the second embodiment described herein is that a light source, instead of a collimation lens, is driven. In other words, in the first embodiment, an incident angle of a parallel illumination light with respect to a diffraction optical element is changed by moving the collimation lens. On the other hand, in the second embodiment described herein, a light source is moved so that a relative position of the light source and a collimation lens is changed, so that an incident angle of a parallel illumination light with respect to a diffraction optical element is changed.

<FIG> is a perspective view showing an overall structure of an illumination device <NUM> according to the second embodiment of the present invention. Similarly to the illumination device <NUM> according to the first embodiment, the illumination device <NUM> is an illumination device having a function of projecting a predetermined lighting pattern E on a predetermined surface to be illuminated U. The surface to be illuminated U is a plane that forms an illuminated area illuminated by the illumination device <NUM>. <FIG> shows that a lighting pattern E formed of a V-shaped graphic pattern is projected on the surface to be illuminated U.

Most of constituent elements of the illumination device <NUM> shown in <FIG> are the same as the constituent elements of the illumination device <NUM> shown in <FIG>. Thus, detailed description of discrete constituent elements is omitted, and a difference from the illumination device <NUM> shown in <FIG> is described. Described also herein is an example in which the illumination device <NUM> is installed on an automobile, and a forward road surface is illuminated such that a lighting pattern E of a direction indicating sign showing its traveling direction is formed.

As illustrated, the illumination device <NUM> comprises a light source <NUM>, a magnifying lens <NUM> that broadens a light beam L1 from the light source <NUM> so as to generate a divergent light L2, a collimation lens <NUM> that shapes a light (the divergent light L2 generated by the magnifying lens <NUM>) from the light source <NUM> so as to generate a parallel illumination light L3, and a diffraction optical element <NUM> that diffracts the parallel illumination light L3 so as to project a lighting pattern E on a surface to be illuminated U (in this example, on a forward road surface). The light source <NUM>, the magnifying lens <NUM>, the collimation lens <NUM> and the diffraction optical element <NUM> are totally the same constituent elements as the light source <NUM>, the magnifying lens <NUM>, the collimation lens <NUM> and the diffraction optical element <NUM> in the illumination device <NUM> shown in <FIG>.

A difference between the illumination device <NUM> shown in <FIG> and the illumination device <NUM> shown in <FIG> is that, in the former, the collimation lens <NUM> is driven by the collimation-lens drive unit <NUM>, while in the latter, the light source <NUM> is driven by a light-source drive unit <NUM>. The light-source drive unit <NUM> is a constituent element that serves a function of supporting the light source <NUM> and driving the same, and has a function of translating the light source <NUM> along a movement plane P that is orthogonal to an optical axis C of a light L1 generated by the light source <NUM> (in the illustrated standard state, the optical axis C of the light L1 is the same as an optical axis C of the divergent light L2 generated by the magnifying lens <NUM>).

Although illustration of a specific structure is omitted, the illumination device <NUM> further has a device housing <NUM>. The device housing is a housing that accommodates the light source <NUM>, the magnifying lens <NUM>, the collimation lens <NUM>, the diffraction optical element <NUM> and the light-source drive unit <NUM>. In the illustrated example, the device housing <NUM> is installed on a front part of an automobile. The device housing <NUM> also has a function of fixedly supporting the collimation lens <NUM>, the diffraction optical element <NUM> and the light-source drive unit <NUM>.

Also in <FIG>, in order to clearly show the fixedly supporting function, discrete parts of the device housing <NUM> are shown by using ground symbols of an electric circuit. The light source <NUM> is supported by the light-source drive unit <NUM> so as to be movable with respect to the device housing <NUM>. In addition, in this example, the magnifying lens <NUM> is fixed on the light source <NUM> instead of the device housing <NUM>. Thus, when the light source <NUM> is moved by the light-source drive unit <NUM>, the magnifying lens <NUM> is moved along with the light source <NUM>. A driving method of the light source <NUM> and the magnifying lens <NUM> by the light-source drive unit <NUM> is described detail in the following §<NUM>.

Also in <FIG>, for the convenience of describing a geometric positional relationship among the respective constituent elements that constitute the illumination device <NUM>, an XYZ three-dimensional orthogonal coordinate system having an X axis, a Y axis and a Z axis that are orthogonal to one another is defined. In the illustrated example, the illumination device <NUM> is installed on the automobile such that its traveling direction corresponds to a positive X direction, and the surface to be illuminated U (forward road surface) is defined on a plane parallel to an XY plane. In order to illuminate the surface to be illuminated U, the light source <NUM> has a function of emitting an illumination light beam L1 in the positive X direction. The collimation lens <NUM> and the diffraction optical element <NUM> are disposed on planes parallel to a YZ plane.

Also in this example, a laser light source is used as the light source <NUM>. A laser beam L1 generated by the light source <NUM> is broadened by the magnifying lens <NUM> so as to generate divergent light L2. In the example shown herein, the laser beam L1 is a luminous flux having a circular section. The divergent light L2 of a conically spreading luminous flux is emergent from the magnifying lens <NUM>. In <FIG>, an optical axis C of the divergent light L2 (an optical axis of the light L2 incident on the collimation lens <NUM>) is drawn with one-dot chain lines. The optical axis C is an axis parallel to the X axis.

The collimation lens <NUM> shapes the conically spreading divergent light L2 so as to generate a parallel illumination light L3, and applies the parallel illumination light L3 to an incident plane Q of the diffraction optical element <NUM>. In the illustrated example, the respective constituent elements are disposed such that the optical axis of the laser beam L1 passes a center point of the collimation lens <NUM>, that the optical axis C of the divergent light L2 (a center axis of the conically spreading divergent luminous flux) passes a center point of the collimation lens <NUM>, and that an optical axis of the parallel illumination light L3 (a center axis of the parallel luminous flux) passes a center point of the diffraction optical element <NUM>.

Thus, in the illustrated example, the optical axis of the laser beam L1, the optical axis C of the divergent light L2 and the optical axis of the parallel illumination light L3 coincide with one another. These axes are axes parallel to the X axis. Also in the second embodiment, this state is referred to as "standard state". In the standard state, the parallel illumination light L3 forms a parallel luminous flux parallel to the X axis, and its section (a section orthogonal to the optical axis) is circular. The diffraction optical element <NUM> is disposed such that its incident plane Q is parallel to the YZ plane. Thus, in the standard state, the parallel illumination light L3 is incident perpendicularly on the incident plane Q of the diffraction optical element <NUM>. As a result, as indicated by broken lines, a circular irradiation area A is formed on the incident plane Q.

As described below, when the light source <NUM> is driven by the light-source drive unit <NUM> to deviate from the standard state, an incident angle of the parallel illumination light L3 with respect to the incident plane Q is changed. In this case, the irradiation area A on the diffraction optical element <NUM> has an elliptic shape.

On the other hand, the diffraction optical element <NUM> has a function of diffracting the parallel illumination light L3, which has been shaped by the collimation lens <NUM> and is applied to the incident plane Q, so as to generate a diffracted light L4, and projecting the lighting pattern E on the surface to be illuminated U by means of the obtained diffracted light L4. To be specific, the diffraction optical element <NUM> is formed of a hologram recording medium which is disposed such that its incident plane Q is parallel to the YZ plane. The hologram recording medium records interference fringes for generating a reconstructed image serving as the lighting pattern E on the surface to be illuminated U parallel to the XY plane. Since such a diffraction optical element <NUM> is a constituent element similar to the diffraction optical element <NUM> shown in <FIG>, detailed description thereof is omitted here.

When the illumination device <NUM> shown in <FIG> is in the standard state, the light source <NUM> generates a light beam L1 having an optical axis parallel to the X axis; the magnifying lens <NUM> generates a divergent light L2 that diverges about the optical axis of the light beam L1; and the collimation lens <NUM> shapes the divergent light L2 so as to generate a parallel illumination light L3, and applies the parallel illumination light L3 to the diffraction optical element <NUM> having the incident plane Q parallel to the YZ plane. Moreover, the light source <NUM> can be translated by the light-source drive unit <NUM> along the movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis C of the light L1 generated by the light source <NUM>. Due to the translation, the illumination device <NUM> is deviated from the standard state, so that an incident direction of the parallel illumination light L3 with respect to the incident plane Q is changed. Thus, as described blew, the lighting pattern E on the surface to be illuminated U can be displaced.

The important feature of the illumination device <NUM> according to the second embodiment is that the light source <NUM> is driven by the light-source drive unit <NUM>. As described above, the collimation lens <NUM>, the diffraction optical element <NUM> and the light-source drive unit <NUM> are fixedly supported by the device housing <NUM>, while the light source <NUM> and the magnifying lens <NUM> are not directly fixed on the device housing <NUM> but are supported to be movable by the light-source drive unit <NUM>.

Thus, a relative position of the light source <NUM> and the magnifying lens <NUM> with respect to the device housing <NUM> is changed by the light-source drive unit <NUM>. This means that a relative position of the light source <NUM> and the magnifying lens <NUM> with respect to the collimation lens <NUM> and the diffraction optical element <NUM>.

To be specific, the light-source drive unit <NUM> has a function of translating the light source <NUM> along the movement plane P that is orthogonal to the optical axis C of the light L1 generated by the light source <NUM>. In the illustrated example, since the light source <NUM> generates the laser beam L1 in a direction parallel to the X axis, the movement plane P orthogonal to the optical axis C of the laser beam L1 is a plane that is parallel to the YZ plane.

Also herein, when a direction (Z-axis direction) orthogonal to the surface to be illuminated U is referred to as a vertical direction d1, and a direction (a direction along the XY plane) parallel to the surface to be illuminated U is referred to as a horizontal direction d2, as shown by the arrows d1 and d2 in <FIG>, the light-source drive unit <NUM> has a vertically driving function of moving the light source <NUM> along the movement plane P in the vertical direction d1, and a horizontally driving function of moving the light source <NUM> along the movement plane P in the horizontal direction d2. By combining the vertically driving function and the horizontally driving function, the light source <NUM> can be translated along the movement plane P, not only in the vertical direction d1 and the horizontal direction d2 but also in a given direction.

As illustrated, the light-source drive unit <NUM> has a drive mechanism <NUM> and a support arm <NUM>, and has a function of supporting the light source <NUM> and translating the light source <NUM> along the movement plane P (a plane parallel to the YZ plane). As such a drive mechanism <NUM>, a general mechanism for moving the support arm <NUM> with the use of a motor and gears can be employed, and detailed description thereof is omitted here.

As described above, since the magnifying lens <NUM> is fixed on the light source <NUM>, when the light-source drive unit <NUM> translates the light source <NUM> along the movement plane P, the magnifying lens <NUM> is translated along therewith. Thus, a relative position of the light beam L1 and the divergent light L2 with respect to the device housing <NUM> is changed, so that their relative position with respect to the collimation lens <NUM> and the diffraction optical element <NUM>, which are fixed on the device housing <NUM>, is also changed. Thus, an incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed.

In the standard state shown in <FIG>, a relative positional relationship among the respective constituent elements is adjusted such that the optical axis C of the divergent light L2 passes the center point of the collimation lens <NUM>, and the divergent light L2 is disposed at a position that is rotational symmetry with respect to the center axis of the collimation lens <NUM>. As a result, the optical axis of the parallel illumination light L3 emergent from the collimation lens <NUM> coincides with the optical axis C of the divergent light L2. The parallel illumination light L3 is incident on the incident plane Q of the diffraction optical element <NUM> in a direction perpendicular thereto, and forms the circular irradiation area A.

However, when the light source <NUM> and the magnifying lens <NUM> are moved by the light-source drive unit <NUM>, the incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed. Thus, the illumination device <NUM> is deviated from the aforementioned standard state. Namely, in the standard state shown in <FIG>, the parallel illumination light L3 emergent from the collimation lens <NUM> becomes a parallel luminous flux that is parallel to the X axis, and is incident on the incident plane Q of the diffraction optical element <NUM> in a direction perpendicular thereto. On the other hand, when the incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed, the parallel illumination light L3 emergent from the collimation lens <NUM> becomes a parallel luminous flux that is inclined with respect to the X axis. Thus, an incident angle of the parallel illumination light L3 with respect to the incident plane Q is changed. As a result, an emergent direction of the diffracted light L4 emergent from the diffraction optical element <NUM> is changed, so that a projection position of the lighting pattern E on the surface to be illuminated U is also changed.

In other words, when the light source <NUM> and the magnifying lens <NUM> are moved, an incident position of the divergent light L2 with respect to the collimation lens <NUM> is changed. In accordance with a displacement direction and a displacement quantity of the incident position, an emergent angle of the parallel illumination light L3 emergent from the collimation lens <NUM> is changed. Thus, an incident angle of the parallel illumination light L3 with resect to the diffraction optical element <NUM> is changed, an emergent direction of the diffracted light L4 emergent from the diffraction optical element <NUM> is changed, and a projection position of the lighting pattern E on the surface to be illuminated U is changed.

In conclusion, also in the second embodiment, similarly to the aforementioned first embodiment, by changing a relative positional relationship between the light source <NUM> and the collimation lens <NUM>, an incident angle of the parallel illumination light L3 with respect to the diffraction optical element <NUM> is changed. Thus, the change in optical phenomenon generated in the diffraction optical element <NUM> which is caused by the movement of the light source <NUM> and the magnifying lens <NUM> is basically similar to the change described in <FIG>.

As described above, as shown by the arrows d1 and d2 in <FIG>, the light-source drive unit <NUM> of the illumination device <NUM> shown in <FIG> has a vertically driving function of moving the light source <NUM> along the movement plane P in the vertical direction d1, and a horizontally driving function of moving the light source <NUM> along the movement plane P in the horizontal direction d2. By combining the vertically driving function and the horizontally driving function, the light source <NUM> can be translated along the movement plane P, not only in the vertical direction d1 and the horizontal direction d2 but also in a given direction.

When the light source <NUM> and the magnifying lens <NUM> are moved in the vertical direction d1, the lighting pattern E on the surface to be illuminated U can be displaced in the X-axis direction. On the other hand, when the light source <NUM> and the magnifying lens <NUM> are moved in the horizontal direction d2, the lighting pattern E on the surface to be illuminated U can be displaced in the Y-axis direction. Thus, similarly to the example shown in <FIG>, by variously displacing the lighting pattern E0 in the standard state, lighting patterns E1 to E3 can be obtained, for example.

Also in the second embodiment, when the lighting pattern E is displaced from the position in the standard state, a profile, in particular, an outline of a luminous flux of the diffracted light L4 from the diffraction optical element <NUM> is slightly changed, so that the lighting pattern E (the V-shaped graphic pattern) displayed on the surface to be illuminated U is slightly deformed in a precise sense. However, as long as the displacement quantity of the light source <NUM> is not extremely large, the deformation of the lighting pattern E is negligible and no serious trouble practically occurs.

In addition, as described in §<NUM>, in connection with the translation of the light source <NUM>, the protrusion phenomenon in which a part of the irradiation area A moves outward the incident plane Q, and there is a possibility that an irradiance of the lighting pattern E decreases. However, as described above, no serious trouble practically occurs. In order to prevent a decrease in irradiance, the size of the diffraction optical element <NUM> is designed slightly larger, such that the irradiation area A formed on the incident plane Q of the diffraction optical element <NUM> does not protrude from the hologram forming surface on the incident plane Q, even when an incident angle of the parallel illumination light L3 is changed (in this case, another problem occurs: the size of the illumination device <NUM> becomes larger as a whole).

Such a protrusion similarly occurs in the collimation lens <NUM>. Namely, in <FIG>, when the outline of the irradiation area of the conically spreading divergent light L2 with respect to the collimation lens <NUM> is designed to reach a point close to the outline of the collimation lens <NUM>, there is a possibility that a part of the divergent light L2 protrudes outside from the collimation lens <NUM> by the movement of the divergent light L2.

<<NUM> Modification Example of Second Embodiment>.

Next, some modification examples of the illumination device <NUM> according to the second embodiment shown in <FIG> are described.

<FIG> is a perspective view showing an overall structure of an illumination device 200RGB according to a modification example of the second embodiment shown in <FIG>. Similarly to <FIG>, an XYZ three-dimensional orthogonal coordinate system is defined. A feature of the illumination device 200RGB is that it comprises three light sources 210R, <NUM> and 210B, and three magnifying lenses 220R, <NUM>, 220B and three collimation lenses 230R, <NUM> and 230B, which are disposed correspondingly to the three light sources. The respective three constituent elements are arranged side by side in the horizontal direction (Y-axis direction). In order to receive parallel illumination lights L3R, L3G and L3B from the respective collimation lenses 230R, <NUM> and 230B, the diffraction optical element 240RGB has a horizontally elongated shape.

The three light sources 210R, <NUM> and 210B are laser light sources that are basically similar to the light source <NUM> shown in <FIG>, but have functions of generating lights of different wavelengths. To be specific, the light source 210R is a red laser light source that generates a red laser beam L1R, the light source <NUM> is a green laser light source that generates a green laser beam L1G, and the light source 210B is a blue laser light source that generates blue laser beam L1B. They emit the respective laser beams L1R, L1G and L1B in a direction parallel to the X axis. These light sources may either be provided as independent components, or be a light emission module in which the light sources are arranged on a common substrate.

The three magnifying lens 220R, <NUM> and 220B and the three collimation lens 230R, <NUM> and 230B are totally the same constituent elements as the magnifying lens <NUM> and the collimation lens <NUM> shown in <FIG>. Thus, the red laser beam L1R generated by the red light source 210R is broadened by the magnifying lens 220R into a red divergent light L2R. The red divergent light L2R is further shaped by the collimation lens 230R into a red parallel illumination light L3R. The red parallel illumination light L3R is applied to a corresponding incident area AR (in the illustrated example, a circular area shown by broken lines) on an incident plane Q of the diffraction optical element 240RGB.

Similarly, a green laser beam L1G generated by the green light source <NUM> is broadened by the magnifying lens <NUM> into a green divergent light L2G. The green divergent light L2G is further shaped by the collimation lens <NUM> into a green parallel illumination light L3G. The green parallel illumination light L3G is applied to a corresponding incident area AG (in the illustrated example, a circular area shown by broken lines) on the incident plane Q of the diffraction optical element 240RGB. In addition, a blue laser beam L1B generated by the blue light source 210B is broadened by the magnifying lens 220B into a blue divergent light L2B. The blue divergent light L2B is further shaped by the collimation lens 230B into a blue parallel illumination light L3B. The blue parallel illumination light L3B is applied to a corresponding incident area AB (in the illustrated example, a circular area shown by broken lines) on the incident plane Q of the diffraction optical element 240RGB.

Similarly to the illumination device <NUM> shown in <FIG>, in the standard state, optical axes of the respective laser beams L1R, L1G, L1B, optical axes CR, CG, CB of the respective divergent lights L2R, L2G, L2B, and optical axes of the respective parallel illumination lights L3R, L3G and L3B are parallel to the X axis. However, when the light sources 210R, <NUM>, 210B are translated, the optical axes of the parallel illumination lights L3R, L3G, L3B are inclined to the X axis, and a shape and a formation position of the corresponding incident area AR, AG, AB are changed.

Similarly to the diffraction optical element <NUM> shown in <FIG>, the diffraction optical element 240RGB has the incident plane Q parallel to the YZ plane, and has a function of diffracting the respective parallel illumination lights L3R, L3G, L3B into a diffracted light L4RGB and projecting a lighting pattern E on a surface to be illuminated U by the obtained diffracted light L4RGB. In the example shown here, hologram interference fringe pattern, which records interference fringes corresponding to a center wavelength of the red laser beam L1R, is recorded in and near the red corresponding irradiation area AR in the incident plane Q of the diffraction optical element 240RGB. A hologram interference fringe pattern, which records interference fringes corresponding to a center wavelength of the green laser beam L1G, is recorded in and near the green corresponding irradiation area AG in the incident plane Q of the diffraction optical element 240RGB. A hologram interference fringe pattern, which records interference fringes corresponding to a center wavelength of the blue laser beam L1B, is recorded in and near the blue corresponding irradiation area AB in the incident plane Q of the diffraction optical element 240RGB.

These respective hologram interference fringes are interference fringes for generating a reconstructed image as a predetermined lighting pattern E (V-shaped graphic pattern) on the surface to be illuminated U parallel to the XY plane. Thus, a red diffracted light from the red corresponding irradiation area AR, a green diffracted light from the green corresponding irradiation area AG and a blue diffracted light from the blue corresponding irradiation area AB each form a reconstructed image as the lighting pattern E at the same position on the surface to be illuminated U. As a result, the lighting pattern E is a colored V-shaped graphic pattern formed by superimposing diffracted lights of three colors.

By adjusting the radiant fluxes [unit: W] of the three laser light sources 210R, <NUM> and 210B, a color of the lighting pattern E can be adjusted. In addition, in order to increase a light intensity, a plurality of the laser light sources may be provided for each of the emission wavelength ranges. In the illustrated example, the single diffraction optical element 240RGB is used. However, instead thereof, three diffraction optical elements 240R, <NUM> and 240B may be used, and the respective parallel incident lights L3R, L3G and L3B may be applied to the corresponding diffraction optical elements 240R, <NUM> and 240B.

The light-source drive unit 250B is a constituent element similar to the light-source drive unit <NUM> shown in <FIG>. Namely, as illustrated, the light-source drive unit 250B has a drive mechanism 251B and a support arm 252B, and has a function of supporting the light source 210B and translating the light source 210B along a movement plane P (a plane parallel to the YZ plane) that is orthogonal to the optical axis of a light generated by it.

Although not shown in <FIG> in order to avoid complexity, light-source drive units 250R and <NUM>, which have the same structure as that of the light-source drive unit 250B, are also provided. The light-source drive unit 250R has a function of supporting the light source 210R and translating the light source 210R along a movement plane P (a plane parallel to the YZ plane) that is orthogonal an optical axis of a light generated by it. Similarly, the light-source drive unit <NUM> has a function of supporting the light source <NUM> and translating the light source <NUM> along a movement plane P (a plane parallel to the YZ plane) that is orthogonal an optical axis of a light generated by it.

Although illustration of a specific structure is omitted, the illumination device 200RGB further comprises a device housing <NUM>. The device housing <NUM> is a housing that accommodates the three light sources 210R, <NUM> and 210B, the three magnifying lenses 220R, <NUM> and 220B, the three collimation lenses 230R, <NUM> and 230B, the one diffraction optical element 240RGB, and the three light-source drive units 250R, <NUM> and 250B. In the example shown here, the device housing <NUM> is installed at a front part of an automobile. The device housing <NUM> also serves a function of fixedly supporting the three collimation lenses 230R, <NUM> and 230B, the one diffraction optical element 240RGB and the three light-source drive units 250R, <NUM> and 250B.

Similarly to <FIG>, in <FIG>, in order to clearly show the fixedly supporting function, the discrete parts of the device housing <NUM> are shown by using ground symbols of an electric circuit. Note that the reference numeral "<NUM>" is omitted for some ground symbols, in order to avoid complexity. The three magnifying lenses 220R, <NUM> and 220B are fixed to the three light sources 210R, <NUM> and 210B. The three light sources 210R, <NUM> and 210B are respectively supported by the light-source drive units 250R, <NUM> and 250B so as to be movable with respect to the device housing <NUM> (translatable along the movement plane P parallel to the YZ plane). Thus, the light source 210R and the magnifying lens 220R are integrally moved, the light source <NUM> and the magnifying lens <NUM> are integrally moved, and the light source 210B and the magnifying lens 220B are integrally moved.

As described above, the illumination device 200RGB according to the modification example has a function of projecting the lighting pattern E as a colored hologram reconstructed image. Thus, by translating the respective light sources 210R, <NUM> and 210B by means of the light-source drive units 250R, <NUM> and 250B in the same direction by the same distance, a projection position of the colored lighting pattern E can be displaced in a desired direction.

It is not necessary that the respective light sources 210R, <NUM> and 210B are moved all together in the same direction by the same distance. They can be moved in different directions by different distances. When the three light sources are moved all together, the colored lighting pattern E can be displaced maintaining its shape, as described above. On the other hand, when the three light sources are separately moved (moved in different directions), a red lighting pattern ER, a green lighting pattern EG and a blue lighting pattern EB (they are all V-shaped graphic pattern) are displaced in different directions, whereby the colored lighting pattern E is decomposed into different colored lighting patterns, and the different colored lighting patterns are separately displayed.

Thus, since it is not necessary that the three light sources are moved all together, one or more of the light source(s) may not be driven but fixed on the device housing <NUM>. For example, in the example shown in <FIG>, as described above, illustration of the light-source drive units 250R and <NUM> is omitted, but the three light-source drive units 250R, <NUM> and 250B are actually provided. However, when this modification example is carried out, it is not necessary that the three light-source drive units 250R, <NUM> and 250B are provided, but at least one light-source drive unit is provided.

For example, when only the light-source drive unit 250B shown in <FIG> is provided, and the two not-shown light-source drive units 250R and <NUM> are not provided, the light sources 210R and <NUM> (and the magnifying lenses 220R and <NUM>) are fixed on the device housing <NUM>, and only the light source 210B can be moved. In this case, in the standard state, the colored lighting pattern E is displayed at the position as shown. When the light source 210B is moved, the lighting pattern E is displayed by red and green mixed color components at the same position, and only a blue lighting pattern E is displaced.

In addition, in the modification example shown in <FIG>, the three light sources 210R, <NUM> and 210B are light sources that generate lights of different wavelengths. However, when colored display is not necessary, it is not necessary that the three light sources are light sources that generate lights of different wavelengths. When lights of the same wavelength are used, a single layer light source <NUM> may be used, and a laser beam generated by the single laser light source <NUM> is split into three beams by using an optical element such as a beam splitter.

In addition, although <FIG> shows the example in which the lights generated by the three light sources 210R, <NUM> and 210B are supplied to the three magnifying lenses 210R, <NUM> and 210B and the three collimation lenses 230R, <NUM> and 230B, respectively, the number of the light sources, the number of the magnifying lenses and the number of the collimation lenses are not necessarily limited to three, but the number may be a given number n.

In the modification example described here, a plurality of light sources, the number of which is n, are provided, and a plurality of collimation lenses, the number of which is n, are provided correspondingly to the respective light sources. The light-source drive unit may translate at least one of the plurality of light sources, such that each collimation lens shapes a light from the corresponding light source into a parallel illumination light and applies the parallel illumination light to a predetermined corresponding irradiation area of the diffraction optical element, and that each corresponding irradiation area diffracts the applied parallel illumination light so as to project a lighting pattern on a surface to be illuminated U.

In the illumination device <NUM> shown in <FIG>, the magnifying lens <NUM> is disposed between the light source <NUM> and the collimation lens <NUM>, a light beam L1 generated by the light source <NUM> is broadened by the magnifying lens <NUM> so as to generate a divergent light L2, the divergent light L2 is given to the collimation lens <NUM>, and the magnifying lens <NUM> is moved together with the light source <NUM>. However, when the light source <NUM> has a function of generating a light having a sectional area sufficient for displaying the lighting pattern E, the magnifying lens <NUM> can be omitted because such a light is not needed to be broadened.

Namely, when an emergent light emergent from the light source <NUM> has a sectional area sufficient for displaying the lighting pattern E, the emergent light may be directly supplied to the collimation lens <NUM>, and the collimation lens <NUM> shapes the emergent light to generate a parallel illumination light L3. The structure in which the magnifying lens is omitted can be also applied to the illumination device 200RGB shown in <FIG>.

In the aforementioned examples and the modification examples, the light source <NUM> is translated by the light-source drive unit <NUM> along the movement plane P that is orthogonal to the optical axis of the light L1 generated by the light source <NUM>. To be more specific, since the optical axis of the light beam L1 generated by the light source <NUM> is an axis parallel to the X axis, the light source <NUM> is translated along the movement plane P parallel to the YZ plane.

However, the direction of motion of the light source <NUM> is not limited to a direction along the movement plane P that is orthogonal to the optical axis of the light generated by the light source <NUM>, and the light source <NUM> may be moved in a given direction. However, when the light source <NUM> is moved in a direction that is "parallel" to the optical axis of the light generated by the light source <NUM>, it is impossible to achieve the object of displacing the lighting pattern E on the surface to be illuminated U.

Thus, the light-source drive unit <NUM> may translate the light source <NUM> in a given direction that is "not parallel" to the optical axis of the light generated by the light source <NUM>. Note that, as described in §<NUM>, when the light source <NUM> can be moved in the vertical direction d1 and the horizontal direction d2, the lighting pattern E can be displaced in a given direction on the surface to be illuminated U. Thus, it is actually sufficient to employ the structure in which the light source <NUM> is translated along the movement plane P that is orthogonal to the optical axis of the light generated by the light source <NUM>.

When the above structure is employed, the configuration of the light-source drive unit <NUM> can be simplified, and the illumination device can be reduced in size as a whole. Thus, it is actually preferable to employ the structure in which the light source <NUM> is translated along the movement plane P that is orthogonal to the optical axis of the light generated by the light source <NUM>.

In the illumination device <NUM> shown in <FIG>, the magnifying lens <NUM> is fixed on the light source <NUM>, so that the light source <NUM> and the magnifying lens <NUM> are integrally moved. However, the magnifying lens <NUM> may be fixed on the device housing <NUM>, and only the light source <NUM> may be moved by the light-source drive unit <NUM>.

When the light source <NUM> is moved, the light beam L1 is moved, although the magnifying lens <NUM> is not moved. Thus, the divergent light L2 is moved, so that an orientation of the parallel illumination light L3 emergent from the collimation lens <NUM> can be changed. This applies to the illumination device 200RGB shown in <FIG>. However, the diameter of the magnifying lens <NUM> is generally smaller than the diameter of the collimation lens <NUM>. Thus, when the distance moved by the light beam L1 is large to a certain degree, there is an impact caused by lens aberration. In addition, when the distance moved by the light beam L1 is large, the light beam L1 is deviated from the magnifying lens <NUM>. Thus, it is practically preferable that the magnifying lens <NUM> is moved together with the light source <NUM>, as described in the aforementioned examples.

As another modification example, the light source <NUM> may be fixed on the device housing <NUM>, and only the magnifying lens <NUM> may be moved by the light-source drive unit <NUM>. Since the light source <NUM> is not moved, the light beam L1 is not moved. However, since the magnifying lens <NUM> is moved, the divergent light L2 is moved, so that an orientation of the parallel illumination light L3 emergent from the collimation lens <NUM> can be changed. This applies to the illumination device 200RGB shown in <FIG>. However, similarly to the above modification example in which only the light source is moved, when the distance moved by the magnifying lens <NUM> is large to a certain degree, there is an impact caused by lens aberration. In addition, when the distance moved by the magnifying lens <NUM> is large, the light beam L1 is deviated from the magnifying lens <NUM>. Thus, it is practically preferable that the magnifying lens <NUM> is moved together with the light source <NUM>, as described in the aforementioned examples.

Some modification examples related to the second embodiment of the present invention has been described, but various modification examples are possible in addition thereto.

In addition, as shown in <FIG> as the modification example, the illumination device according to the second embodiment can have a plurality of light sources. In this case, at least one of the light sources may be supported so as to be movable in a direction that is not parallel to an optical axis of a light emergent from the light source. However, it is practically preferable that the light source supported so as to be movable is supported so as to be movable in a plane that is orthogonal to an optical axis of a light emergent from the light source.

Further, in the illumination device <NUM> shown in <FIG>, one magnifying lens <NUM> and one collimation lens <NUM> are arranged for one light source <NUM>. On the other hand, in the modification example in which a plurality of light sources are used, at least either of the magnifying lens <NUM> and the collimation lens <NUM> may be shared by the plurality of light sources.

Claim 1:
An illumination device (<NUM>) configured to project a predetermined lighting pattern (E) on a surface to be illuminated (U), comprising:
a light source (<NUM>);
a collimation lens (<NUM>) configured to shape a light (L2) from the light source (<NUM>) into a parallel illumination light (L3);
a diffraction optical element (<NUM>) configured to diffract the parallel illumination light (L3) so as to project the lighting pattern (E) on the surface to be illuminated (U); and
a collimation-lens drive unit (<NUM>) configured to support the collimation lens (<NUM>) and drive the same;
wherein the collimation-lens drive unit (<NUM>) is configured to translate the collimation lens (<NUM>) in a predetermined direction that is not parallel to an optical axis (C) of a light incident on the collimation lens (<NUM>),
wherein the collimation-lens drive unit (<NUM>) is configured to translate the collimation lens (<NUM>) along a movement plane (P) that is orthogonal to the optical axis (C) of the light incident on the collimation lens (<NUM>),
the illumination device (<NUM>) further comprising a magnifying lens (<NUM>) disposed between the light source (<NUM>) and the collimation lens (<NUM>), wherein:
the light source (<NUM>) is configured to generate a light beam (L1), the magnifying lens (<NUM>) is configured to broaden the light beam (L1) so as to generate a divergent light (L2), and the collimation lens (<NUM>) is configured to shape the divergent light (L2) so as to generate the parallel illumination light (L3),
an XYZ three-dimensional coordinate system having an X axis, a Y axis and a Z axis that are orthogonal to one another is defined;
the light source (<NUM>) is configured to generate the light beam (L1) having an optical axis (C) parallel to the X axis;
the magnifying lens (<NUM>) is configured to generate the divergent light (L2) that diverges about the optical axis (C);
the diffraction optical element (<NUM>) has an incident plane (Q) parallel to a YZ plane; and
the collimation-lens drive unit (<NUM>) is configured to drive the collimation lens (<NUM>) such that the collimation lens (<NUM>) is translated along a movement plane (P) parallel to the YZ plane, so that an incident direction of the parallel illumination light (L3) with respect to the incident plane (Q) is changed by the driving operation.