lighting equipment

Abstract

To provide a projection lens that can suppress unevenness of the intensity of projection light.SOLUTION: The projection lens according to an embodiment of the present disclosure is for projecting light which an array light source with a plurality of light sources emit, and has an opening. Of the light projected by the projection lens, Central light, which passes through the center of the opening, and peripheral light, which passes through the peripheries of the opening, reach the same position on the image surface of the projection lens.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure , Teru Regarding the lighting device. [Background technology]

[0002] A projection lens that projects light emitted from an array light source having multiple light sources is known. In such a projection lens, unevenness in the light intensity corresponding to the spacing between the multiple light sources may occur in the projected light.

[0003] Furthermore, in order to suppress unevenness in the light intensity of the projected light, a configuration has been disclosed in which the image of the light source formed by the projection lens is defocused (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 158886 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration of Patent Document 1 may not be able to suppress unevenness in the light intensity of the projected light.

[0006] Therefore, an object of the present disclosure is to provide a projection lens that can suppress unevenness in the light intensity of projected light. [Means for solving the problem]

[0007] A projection lens according to one embodiment of the present disclosure is a projection lens that projects light emitted by an array light source having a plurality of light sources, and includes an opening, and of the light projected by the projection lens, central light that passes through the center of the opening and peripheral light that passes through the periphery of the opening reach the same position on the image plane of the projection lens.

[0008] An illumination device according to another embodiment of the present disclosure includes an array light source having a plurality of light sources and the projection lens. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a projection lens that can suppress unevenness in the light intensity of projected light. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of the configuration of a lighting device according to an embodiment. [Figure 2] 1 is a diagram illustrating a configuration example of an LED array according to an embodiment. [Figure 3] This figure shows the characteristics of reducing uneven light intensity due to differences in the point images that make up the image. Fig. 3(a) shows an exit plane image consisting of ideal point images (point images with no distribution), Fig. 3(b) shows an exit plane image consisting of distributed point images (point images with a distribution), and Fig. 3(c) shows adjacent exit plane images. [Figure 4] These are diagrams showing examples of a collection of distributed point images, where Fig. 4(a) shows a flat-profile point image, Fig. 4(b) shows a convex-profile point image, Fig. 4(c) shows a concave-profile point image, and Fig. 4(d) shows an exit plane image profile consisting of these point images. [Figure 5] These are light intensity distribution maps of adjacent exit surface images, where Fig. 5(a) shows a flat profile point image, Fig. 5(b) shows a convex profile point image, and Fig. 5(c) shows a concave profile point image. [Figure 6] 6(a) and 6(d) are diagrams showing examples of the characteristics of a projection lens, in which FIG. 6(a) shows the ray trajectory of a typical projection lens, FIG. 6(b) shows the image plane light intensity distribution of FIG. 6(a), FIG. 6(c) shows the ray trajectory of a projection lens according to an embodiment, and FIG. 6(d) shows the image plane light intensity distribution of FIG. 6(c). [Figure 7] 4A and 4B are diagrams showing lateral aberration of the projection lens according to the embodiment. [Figure 8] 8A to 8E are diagrams showing examples of simulation results of the lateral aberration of the projection lens for each object-side angle of view, and show lateral aberration diagrams at each point from the central axis to the maximum height of the projection lens. [Figure 9] FIG. 10 is a diagram showing an allowable range of positional deviation between a central light and a peripheral light. [Figure 10] 10A and 10B are diagrams illustrating an example of projected light, where FIG. 10A shows a captured image of projected light according to a comparative example, and FIG. 10B shows a captured image of projected light according to the embodiment. [Figure 11] 10A and 10B are diagrams showing examples of the height at which light passes through the opening and final lens surface of the projection lens; [Figure 12] FIG. 1 is a diagram showing lateral aberration of the projection lens described in Patent Document 1. [Figure 13] 13A to 13C are diagrams showing examples of the relationship between the area of the exit surface image and the area of the distributed point image by a projection lens according to a modified example, where FIG. 13A is a first example, FIG. 13B is a second example, and FIG. 13C is a third example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, parts with the same reference numerals appearing in multiple drawings indicate the same or equivalent parts or members, and redundant description will be omitted as appropriate.

[0012] Furthermore, the embodiments shown below are examples of projection lenses and lighting devices that embody the technical concepts of the present invention, and the present invention is not limited to the embodiments shown below. The dimensions, materials, shapes, relative positions, etc. of the components described below are intended to be illustrative and not to limit the scope of the present invention unless otherwise specified. Furthermore, the sizes and positional relationships of components shown in the drawings may be exaggerated for clarity.

[0013] The projection lens according to the embodiment projects light emitted from an array light source having multiple light sources. In the embodiment, the projection lens is configured so that, of the light projected by the projection lens, central light passing through the center of an opening included in the projection lens and peripheral light passing through the periphery of the opening reach the same position on the image plane of the projection lens. With this configuration, the image of the light source formed by the projection lens is set to a predetermined state on the image plane, thereby suppressing uneven light intensity corresponding to the spacing between the multiple light sources in the array light source.

[0014] In the following, an embodiment will be described using an illumination device having a projection lens as an example. In the following drawings, directions may be indicated by X, Y, and Z axes. The X direction along the X axis indicates a specific direction within an array plane in which multiple light sources in the array light source of the illumination device are arranged. The Y direction along the Y axis indicates a direction perpendicular to the X direction within the array plane, and the Z direction along the Z axis indicates a direction perpendicular to the array plane.

[0015] Furthermore, the direction in which the arrow points in the X direction is referred to as the +X direction, and the direction opposite to the +X direction is referred to as the -X direction; the direction in which the arrow points in the Y direction is referred to as the +Y direction, and the direction opposite to the +Y direction is referred to as the -Y direction; and the direction in which the arrow points in the Z direction is referred to as the +Z direction, and the direction opposite to the +Z direction is referred to as the -Z direction. In the embodiment, the array light source emits light toward the +Z direction, as an example. This does not limit the orientation of the projection lens and lighting device when in use, and the orientation of the projection lens and lighting device is arbitrary.

[0016] [Embodiment] <Configuration Example of Illumination Device 100> First, the configuration of an illumination device 100 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram illustrating an example of the configuration of the illumination device 100. As shown in Fig. 1, the illumination device 100 has an LED (Light Emitting Diode) array 1, a control unit 2, and a projection lens 3. The LED array 1 emits light in the +Z direction in response to a drive voltage from the control unit 2. The projection lens 3 projects the light emitted by the LED array 1 onto an image plane Im.

[0017] The lighting device 100 is, for example, an indoor lighting device, a device that illuminates the interior and exterior walls of a building for spatial presentation, an in-vehicle lighting device such as a headlamp or a communication lamp, or a display device such as a projector, which is a device that provides illumination or projection.

[0018] The image plane Im is a plane that is conjugate with the light emission plane of the LED array 1 via the projection lens 3. When the lighting device 100 is used for wall lighting or for lighting or projection for a display device, the image plane Im corresponds to the surface onto which light is projected, such as a wall surface. When the lighting device 100 is used for interior lighting or an in-vehicle headlight, the image plane Im corresponds to an imaginary plane in space. Note that this imaginary plane includes an imaginary plane corresponding to infinity. When the lighting device 100 is used for an in-vehicle communication lamp, the image plane Im corresponds to the road surface.

[0019] The LED array 1 and the projection lens 3 are held in a housing. The control unit 2 may be provided inside the housing or may be provided separately from the housing.

[0020] The LED array 1 is an example of an array light source having a plurality of LEDs, and the LEDs are an example of a light source. The LED array 1 has a plurality of LEDs arranged at approximately equal intervals within an array plane (within the XY plane). Each LED is electrically connected to the control unit 2 via a cable or the like, and can independently emit light when a drive voltage is applied from the control unit 2.

[0021] The light emitted by the LED array 1 is, for example, white light. However, it is not limited to this and may be monochromatic light, or various types of white light such as incandescent white, neutral white, and daylight white can be selected. The type of array light source is also not limited to an LED array; an array light source can also be configured by arranging multiple fluorescent lamps in an array or bundling multiple optical fibers in an array.

[0022] The projection lens 3 has a lens L1, a lens L2, and a lens L3. The projection lens 3 can convert the light emitted from the LED array 1 and incident on the projection lens 3 into desired projection light that is emitted from the projection lens 3. Here, converting light means changing the direction in which light travels, and for example, means changing the incident light into desired focused light, collimated light, or divergent light.

[0023] Each lens is fixed in a lens barrel 4 in a predetermined positional relationship and is held in the housing via the lens barrel 4. However, the projection lens 3 may be fixed and held directly to the housing without using the lens barrel 4.

[0024] Of the projection lenses 3, lens L1 is a biconvex spherical lens with positive refractive power. Lens L2 is a meniscus aspherical lens with negative refractive power. Lens L3 is a biconvex spherical lens with positive refractive power. Each lens can be made of various materials such as glass or plastic, appropriately selected depending on the intended use of the illumination device 100.

[0025] The central axis A indicated by the dashed line in FIG. 1 is an axis passing through the center of the projection lens 3 and corresponds to the optical axis of the projection lens 3. The opening S is a part of the projection lens 3, and is a circular part located in a plane of the projection lens 3 that is approximately parallel to the arrangement plane. The opening S has the function of defining the effective area of light passing through the projection lens 3. However, the shape of the opening S is not limited to a circular shape, and various shapes such as a rectangular shape, a polygonal shape, or a cat's eye shape can be used.

[0026] Of the light incident on the projection lens 3, the light that reaches the inside of the opening S (toward the central axis A) passes through the opening S to form the light projected by the projection lens 3. On the other hand, the light that reaches the outside of the opening S does not pass through the opening S and does not contribute to the light projected by the projection lens 3.

[0027] The location of such an opening S is determined by a member such as an aperture stop provided in the optical path of the projection lens 3. Alternatively, the location of the opening S is determined by a light-blocking film or a reflective film formed on the lens surface so that light reaching the outside of the opening S cannot pass through. The location of the opening S is also determined by the shape of the lens surface that refracts or reflects light reaching the outside of the opening S in a direction that prevents it from exiting the projection lens 3.

[0028] FIG. 1 illustrates an example of a projection lens 3 in which an opening S is provided on the +Z direction side of the lens L2. In FIG. 1, a central light 300 corresponds to the chief ray of the projection lens 3 and is light that passes through approximately the center of the opening S. Furthermore, an upper marginal light 301 is light that passes through approximately the periphery on the +Y direction side of the projection lens 3, and a lower marginal light 302 is light that passes through approximately the periphery on the -Y direction side of the projection lens 3. The upper marginal light 301 and the lower marginal light 302 are each examples of marginal light that passes through the periphery of the opening S. FIG. 1 illustrates the central light 300, the upper marginal light 301, and the lower marginal light 302 in a plane (meridian plane) that includes the central axis A. The plane that includes the central axis A corresponds to a plane parallel to the paper surface in FIG. 1.

[0029] Here, central light 300 refers to light that passes through a circular region at the center of opening S, the region having a diameter that is 10% or less of the diameter of opening S. Furthermore, peripheral light, including upper peripheral light 301 and lower peripheral light 302, refers to light that passes through an annular region at the periphery of opening S, the region having a radial width that is 10% or less of the diameter of opening S. Note that in this embodiment, a circular opening S is exemplified, and therefore the ratio of central light to peripheral light is shown based on the diameter of opening S. However, if opening S is not circular, the size corresponding to the shape of opening S will be used as the basis. Furthermore, if opening S is not circular, the peripheral light will not be annular, but will be light that passes through a band-like region corresponding to the shape of opening S.

[0030] The position of the opening S is not limited to the +Z direction side of the lens L2, but is appropriately determined to a desired position in the optical path of the projection lens 3 according to the specifications of the projection lens 3.

[0031] Table 1 shows an example of the main specification values of the projection lens 3.

[0032] [Table 1]

[0033] Note that the specification values shown in Table 1 are just an example, and the specification values of the projection lens 3 can be determined appropriately depending on the intended use of the lighting device 100. Furthermore, the number of lenses constituting the projection lens 3, the refractive power of each lens, the arrangement, whether a spherical or aspherical surface is used, etc. are not limited to those described in Fig. 1, and can be determined appropriately depending on the intended use of the lighting device 100. The surface shape and surface spacing of each lens in the projection lens 3 are determined according to the configuration and specifications of the projection lens 3 so as to achieve the characteristics and functions described below.

[0034] The lateral aberration diagrams shown below, the height at which light rays pass through the lens surface, and the position at which they reach on the image surface will be explained based on the backward ray tracing shown in Figure 1. In other words, the explanation will be based on the assumption that light rays enter the projection lens 3 from the image surface side.

[0035] Next, the configuration of the LED array 1 will be described with reference to Fig. 2. Fig. 2 is a diagram illustrating an example of the configuration of the LED array 1, and is a diagram of the arrangement plane of the LED array 1 viewed from the +Z direction side.

[0036] As shown in FIG. 2, the LED array 1 has a total of 25 LEDs 11 arranged in the array plane, five in the X direction and five in the Y direction. The emission surface 12 indicated by the dashed line inside each LED 11 indicates the area from which each LED 11 emits light. The LEDs 11 emit light in the +Z direction from their emission surfaces 12. The number and arrangement of the LEDs 11 are not limited to this and can be selected as appropriate. The LEDs can also be arranged in a one-dimensional array.

[0037] Here, since it is not possible to completely eliminate the gap between the emission surfaces 12 of each LED 11 within the array plane, non-emission areas 13 that do not emit light are included between adjacent emission surfaces 12 in the LED array 1, as shown in Figure 2.

[0038] Due to the presence of this non-emission area 13, the light intensity of the light projected by the projection lens decreases in the area on the image plane Im (see FIG. 1) corresponding to the image of the non-emission area 13, which may result in uneven light intensity. The area where the light intensity of the projected light decreases corresponding to the image of the non-emission area 13 is a dark linear area, and is therefore called a dark line.

[0039] In this embodiment, uneven light intensity caused by such dark lines is suppressed by providing the projection lens 3 with predetermined characteristics and setting the image formed by the projection lens 3 to a predetermined state. The predetermined characteristics of the projection lens 3 and the method for providing them are described below.

[0040] <Examples of characteristics of the projection lens 3 and how to provide them> The characteristics of the projection lens 3 and the method of providing them will be described with reference to FIGS. 3 to 8 and also with reference to the configuration diagram of FIG. 1 as needed.

[0041] (Reduction of uneven light intensity due to differences in point images) First, Fig. 3 is a diagram illustrating the reduction characteristics of light intensity unevenness due to differences in the point images that make up the image. Fig. 3(a) is a diagram showing an example of an exit plane image consisting of ideal point images, Fig. 3(b) is a diagram showing an example of an exit plane image consisting of distributed point images, and Fig. 3(c) is a diagram showing an example of adjacent exit plane images. Note that the horizontal axis of the graph showing the light intensity distribution in Fig. 3 represents the position in the image plane, and the vertical axis represents the light intensity. This also applies to the graphs showing the light intensity distribution that will be shown hereinafter. Here, an ideal point image refers to a point image that does not have a distribution (spread), and a distributed point image refers to a point image that has a distribution (spread).

[0042] The ideal exit surface image 31 in FIG. 3(a) shows an image of the LED exit surface of the LED array 1 by the projection lens 3, and is a planar view of the ideal exit surface image on the image plane Im. The ideal profile 31p is the light intensity distribution of the AA cross section of the ideal exit surface image 31. In the ideal profile 31p, the light intensity increases sharply in the region corresponding to the image of the exit surface. Here, the "profile" refers to the one-dimensional light intensity distribution obtained by cutting the two-dimensional light intensity distribution of the light beam within the cross section when the light beam is cut along a plane perpendicular to the direction of travel of the light beam, and then further cutting the two-dimensional light intensity distribution of the light beam along a plane including the central axis of the light beam. Such a one-dimensional light intensity distribution can also be referred to as a cross-sectional light intensity distribution.

[0043] The distributed exit surface image 32 in Figure 3(b) shows an image formed by the projection lens 3 of the LED exit surface of the LED array 1, and is a planar view of the exit surface image made up of distributed point images on the image plane Im. The distribution profile 32p is the light intensity distribution of the BB cross section in the distributed exit surface image 32. The distributed exit surface image 32 is broader than the ideal exit surface image 31, and in the distribution profile 32p, the light intensity gradually changes in the areas corresponding to the edges of the exit surface image.

[0044] Figure 3(c) shows the ideal profile 31p (dashed line) and distribution profile 32p (dashed line) of two adjacent exit surfaces. The light intensity drops sharply between adjacent ideal profiles 31p, reaching nearly zero. This results in a high-contrast dark line between adjacent ideal profiles 31p.

[0045] On the other hand, between adjacent distribution profiles 32p, the light intensity does not drop sharply, and light intensity remains in both distribution profiles 32p. Therefore, by adding up both light intensities, light intensity 33 is secured as shown in FIG. 3(c). As a result, the drop in light intensity between adjacent distribution profiles 32p is alleviated, and the contrast of dark lines is reduced. In other words, light intensity unevenness due to dark lines and the like is suppressed. In this embodiment, such a characteristic of reducing light intensity unevenness due to differences in point images is utilized.

[0046] (Example of formation of an exit plane image by a collection of distributed point images) Next, Fig. 4 illustrates an example of a collection of distributed point images. Fig. 4(a) shows a flat profile point image, Fig. 4(b) shows a convex profile point image, Fig. 4(c) shows a concave profile point image, and Fig. 4(d) shows an exit plane image profile consisting of these point images.

[0047] Here, the point image refers to an image formed when light emitted from an arbitrary point within the LED emission surface of the LED array 1 is projected onto the image plane Im by the projection lens 3. There are various distribution (spread) states of point images, and Figures 4(a) to 4(c) show point images in different states.

[0048] Fig. 4(a) shows a distribution point image with a flat profile. The flat-profile point image 41 in Fig. 4(a) is a planar view of the distribution point image on the image plane Im, and the flat profile 41p is the light intensity distribution of the CC cross section in the flat-profile point image 41. In the flat-profile point image 41, a flat, top-hat shaped profile is obtained.

[0049] The term "flat" in the embodiments means that when a light beam is cut along a plane perpendicular to the direction of travel of the light beam, the peak light intensity in the two-dimensional light intensity distribution of the light beam obtained within the cut surface is spatially constant. Spatially constant means that the light intensity is equal at each position within the cut surface. However, "flat" does not require that the spatial light intensity be completely constant (the light intensity at each position within the cut surface is completely consistent), and differences in light intensity that are generally considered to be errors are acceptable.

[0050] To evaluate whether a light intensity distribution is flat, for example, a light beam emitted from a point light source such as a pinhole placed at a position corresponding to the exit surface of the LED array 1 is allowed to reach the image plane Im through the projection lens 3. When the light beam is received by a light receiving element such as a CCD placed at a position corresponding to the image plane Im, if the PP (Peak to Peak) value of the luminance distribution of the image (spot image) of the light beam captured by the CCD is equal to or less than the luminance noise of the CCD, the profile can be said to be "flat."

[0051] For example, the PP value is obtained from the brightness distribution obtained by averaging the brightness for each pixel in the spot image, and the CCD brightness noise is obtained using the standard deviation 3σ of the time variation in brightness. By comparing the two, it is possible to determine whether the profile is "flat." Note that instead of a CCD, a measuring instrument such as a beam profiler can be used to receive the light beam, and whether the profile is "flat" can be determined based on the light reception results.

[0052] 4(b) is a diagram showing a convex profile point image with a convex profile shape. The convex profile point image 42 is a planar view of the distribution point image on the image plane Im, and the convex profile 42p is a profile of the DD cross section of the convex profile point image 42. In the convex profile point image 42, the light intensity increases toward the center.

[0053] 4(c) is a diagram showing a distributed point image with a concave profile shape. The concave profile point image 43 is a planar view of the distributed point image on the image plane Im, and the concave profile 43p is a profile of the EE cross section of the concave profile point image 43. In the concave profile point image 43, the light intensity decreases toward the center.

[0054] Here, the exit surface image is formed by gathering multiple point images on the image plane Im, which are the result of light emitted from each point on the LED exit surface. Figure 4(d) shows the profile of the exit surface image, which is formed by gathering multiple distributed point images corresponding to multiple points on one LED exit surface of the LED array 1 on the image plane Im.

[0055] 4(d), the flat exit surface profile 41com indicates an exit surface profile formed by a collection of multiple flat-profile point images 41 on the image surface Im. The convex exit surface profile 42com indicates an exit surface profile formed by a collection of multiple convex-profile point images 42 on the image surface Im. The concave exit surface profile 43com indicates an exit surface profile formed by a collection of multiple concave-profile point images 43 on the image surface Im.

[0056] As shown in Figure 4(d), the exit surface profile differs depending on the distribution state. Therefore, it can be seen that the exit surface profile can be controlled by setting the distribution to a predetermined state. Furthermore, the slope 41c in the profile distribution of the flat exit surface profile 41com has a more linear shape than the slope 42c of the convex exit surface profile 42com and the slope 43c of the concave exit surface profile 43com.

[0057] (Example of the relationship between distribution characteristics and light intensity between adjacent exit surface images) Next, Fig. 5 shows an example of the light intensity distribution of two adjacent exit surface images: Fig. 5(a) is a flat profile point image, Fig. 5(b) is a convex profile point image, and Fig. 5(c) is a concave profile point image.

[0058] The light intensity 51 between the exit surface profiles 51a and 51b in Fig. 5(a) is greater than the light intensity 52 between the exit surface profiles 52a and 52b in Fig. 5(b). Also, an inflection point is observed in the distribution of the light intensity 53 between the exit surface profiles 53a and 53b in Fig. 5(c), and the unevenness of the light intensity is noticeable.

[0059] Therefore, by forming an exit surface profile using a flat profile point image having a flat light intensity distribution as shown in Figure 5(a), it is possible to prevent the light intensity between adjacent exit surface images from decreasing relative to the peak light intensity of each exit surface image, compared to the case of point images having a convex or concave light intensity distribution, and it is possible to effectively suppress light intensity unevenness due to dark lines, etc.

[0060] (Example of flattening the light intensity distribution of a distributed point image) Next, the characteristics of the projection lens 3 for flattening the light intensity distribution of the distributed point image will be described. Fig. 6 is a diagram for explaining an example of the projection lens characteristics, in which Fig. 6(a) shows the ray trajectories of a general projection lens 3X, Fig. 6(b) shows the image plane light intensity distribution of Fig. 6(a), Fig. 6(c) shows the ray trajectories of the projection lens 3 according to this embodiment, and Fig. 6(d) shows the image plane light intensity distribution of Fig. 6(c).

[0061] In order to simplify the drawings, the projection lenses in Figures 6(a) and 6(c) are shown as a single lens. Also, components having the same functions in Figures 6(a) and 6(c) are given the same part numbers (part symbols).

[0062] As shown in Fig. 6(a), the projection lens 3X imparts distribution to the point image by converging the light projected by the projection lens at a converging point 5X on the -Z direction side of the image plane Im, regardless of the height (incident height) at which the light passes through the opening S. In this case, the distributed point image has a convex profile, as shown in Fig. 6(b).

[0063] 6(c), the projection lens 3 causes the central light 300 and the upper peripheral light 301 of the light projected by the projection lens 3 to reach the same position h0 on the image plane Im, thereby imparting a predetermined distribution characteristic to the point image.

[0064] Furthermore, within the plane including the central axis A, the projection lens 3 causes intermediate light 303, which passes through the middle between the periphery and the center of the opening S, to reach a position hmax on the image plane Im that is farthest from the positions where the central light 300 and the upper peripheral light 301 reach. This also imparts a predetermined distribution characteristic to the point image.

[0065] By doing this, the light rays from the center to the middle of the opening S and the light rays from the middle to the periphery overlap, and the distributed point image formed by the projection lens 3 has a flat light intensity distribution, as shown in Fig. 6(d). For example, the distributed point image formed on the image plane Im by light emitted from the point where the central axis A of the projection lens 3 intersects with the exit surface of the LED array 1 can have a flat light intensity distribution.

[0066] Next, Fig. 7 is a diagram of lateral aberration of the projection lens 3. The horizontal axis indicates the position at the aperture S through which light projected by the projection lens 3 passes, normalized by the maximum distance from the central axis A. On the horizontal axis, 0 corresponds to the center of the aperture S, and 1.0 corresponds to the periphery of the aperture S. The vertical axis indicates the position on the image plane Im at which light projected by the projection lens 3 reaches.

[0067] As shown in Fig. 7, the lateral aberration of the projection lens 3 has a sinusoidal shape. Specifically, light passing through the center of the opening S, i.e., central light 300 whose light passage position in the opening S is 0, arrives at position h0 on the image plane Im. Light passing through the periphery of the opening S, i.e., upper marginal light 301 whose light passage position in the opening S is 1.0, arrives at position h0 on the image plane Im. Therefore, the central light 300 and upper marginal light 301 arrive at the same positions on the image plane Im.

[0068] Furthermore, in a plane including the central axis A, intermediate light 303 (see FIG. 6(c)), which passes through the middle between the center and the periphery of the aperture S, i.e., the light passing position at the aperture S is 0.5, reaches position hmax on the image plane Im.

[0069] In designing the projection lens 3, for example, the number of lenses, the material of each lens, and specification values such as focal length, Fno, and back focus are determined depending on the intended use of the illumination device 100. Then, as an example, the arrival positions on the image plane Im of the above-mentioned central light 300, upper marginal light 301, and intermediate light 303 are set as target values, and in a ray tracing simulation, calculation processing is performed to converge the target values using the shape and surface spacing of each lens surface in the projection lens 3 as variables. This determines the optimal values for the shape and surface spacing of each lens surface in the projection lens 3, making it possible to design a projection lens 3 that flattens the light intensity distribution of a distributed point image.

[0070] <Examples of various data for the lighting device 100> Next, as various data of the illumination device 100, the results of simulating the lateral aberration of the projection lens 3 and the results of capturing the projection light will be described.

[0071] (Example of lateral aberration simulation results) Fig. 8 shows an example of the simulation results of the lateral aberration of the projection lens 3 for each object-side angle of view. Fig. 8(a) shows the case when the object-side angle of view is 0 degrees, Fig. 8(b) shows the case when the object-side angle of view is 4.3 degrees, Fig. 8(c) shows the case when the object-side angle of view is 9.6 degrees, Fig. 8(d) shows the case when the object-side angle of view is 14.4 degrees, and Fig. 8(e) shows the case when the object-side angle of view is 18.2 degrees. Figs. 8(a) to 8(e) also show the lateral aberration in the X direction (graph on the right) and the Y direction (graph on the left), respectively.

[0072] At any object-side angle of view, the central light and upper peripheral light reach the image plane Im with a positional deviation within the allowable range, and the shape of the lateral aberration is close to a sine wave.

[0073] Here, it may be difficult to perfectly align the positions of the central light 300 and the upper marginal light 301 on the image plane Im due to manufacturing errors such as shape errors and assembly errors of the projection lens 3. On the other hand, even if the positions of the central light 300 and the upper marginal light 301 on the image plane Im are not perfectly aligned, an effect equivalent to that obtained when the positions are aligned may be obtained as long as the positional deviation is within an allowable range.

[0074] 9 shows an example of a simulation result for explaining the allowable range of the positional deviation on the image plane Im between the central light 300 and the upper marginal light 301. FIG. 9 can be viewed in the same way as FIG. 8. According to this simulation, the allowable range of the positional deviation Δh on the image plane Im between the central light 300 and the upper marginal light 301 in the projection lens 3 is, for example, 0.07 mm or less.

[0075] Note that if circular central light 300 having a diameter equal to or less than 10% of the diameter of opening S and annular peripheral light having a radial width equal to or less than 10% of the diameter of opening S and including upper peripheral light 301 overlap even slightly at the image plane position, it can be said that "central light 300 and upper peripheral light 301 reach the same position on the image plane of the projection lens." Even for the central light and peripheral light for each object-side angle of view shown in Figure 8, the circular central light having a diameter equal to or less than 10% of the diameter of opening S and the annular peripheral light having a radial width equal to or less than 10% of the diameter of opening S at least partially overlap at the image plane position. Note that if the shape of opening S is not circular, the peripheral light will not be circular but will be a band-like region according to the shape of opening S.

[0076] (Example of projected light) Next, Fig. 10 is a diagram illustrating an example of projected light. Fig. 10(a) shows a captured image of projected light on an image plane by an illumination device 100X according to a comparative example, and Fig. 10(b) shows a captured image of projected light on an image plane by an illumination device 100 according to this embodiment. The comparative example is projected light on an image plane by an illumination device 100X that does not impart a predetermined distribution characteristic. The captured image refers to an image captured by a camera of a projection image obtained when projecting projection light onto a projection surface such as a screen.

[0077] As shown in FIG. 10(a), with the illumination device 100X, dark line images 102 are visible between adjacent exit surface images 101, and the light intensity unevenness of the projected light is large. The dark line contrast (Id / Ip×100), which represents the ratio of the average light intensity Id in the area of the dark line image 102 to the average light intensity Ip in the image area other than the dark line image 102, was 84% for the light projected by the illumination device 100X. Furthermore, when a distribution characteristic due to defocus was imparted to the illumination device 100X, the dark line contrast was 91%. Note that a larger value of the dark line contrast indicates a lower contrast of the dark line and more suppressed light intensity unevenness.

[0078] 10(b), in the illumination device 100, the dark lines and LED images were almost invisible, and the dark line contrast of the light projected by the illumination device 100 was 97%. The unevenness in light intensity was effectively suppressed, and the projection light had a more uniform light intensity than the light projected by the illumination device 100X.

[0079] (Example of the height at which light passes through the opening S and the final lens surface Sn in the projection lens 3) Next, to illustrate the characteristics of the projection lens 3, the height (position in the Y direction) at which light incident on the projection lens 3 passes through the opening S and the height at which light passes through the final lens surface Sn will be described. Fig. 11 is a diagram illustrating an example of the passing height of light at the opening S and the final lens surface Sn in the projection lens 3.

[0080] Fig. 11 shows the behavior of a laser beam, which is a substantially parallel beam with a beam diameter of approximately 0.5 mm, when it enters the projection lens 3 within a plane including the central axis A. Fig. 11 also shows the projection lens 3 in a simplified form, showing only the first lens surface S1, the opening S, and the final lens surface Sn. In Fig. 11, the radius Ds represents the radius of the opening S, and the radius Dn represents the radius of the final lens surface Sn.

[0081] 11, a central laser beam 111 is light that passes through the center of the opening S. The central laser beam 111 passes through the opening S at a height of 0 or more and h1 or less, and passes through the final lens surface Sn at a height of 0 or more and h6 or less.

[0082] Expressed as a ratio to the respective radii of the opening S and the final lens surface Sn, the height at which the central laser beam 111 passes through the opening S is equal to or greater than 0 and equal to or less than h1 / Ds. Also, the height at which the central laser beam 111 passes through the final lens surface Sn is equal to or greater than 0 and equal to or less than h6 / Dn.

[0083] The peripheral laser beam 112 is light that passes through the peripheral edge of the opening S. The peripheral laser beam 112 passes through the opening S at a height of not less than h3 and not more than h2, and passes through the final lens surface Sn at a height of not less than h8 and not more than h7.

[0084] Expressed as a ratio to the respective radii of the opening S and the final lens surface Sn, the height at which the peripheral laser beam 112 passes through the opening S is equal to or greater than h3 / Ds and equal to or less than h2 / Ds. The height at which the peripheral laser beam 112 passes through the final lens surface Sn is equal to or greater than h8 / Dn and equal to or less than h7 / Dn.

[0085] The intermediate laser beam 113 is light that passes between the center and the periphery of the opening S. The intermediate laser beam 113 passes through a height of h5 or more and h4 or less at the opening S, and passes through a height of h10 or more and h9 or less at the final lens surface Sn.

[0086] Expressed as a ratio to the respective radii of the opening S and the final lens surface Sn, the height at which the intermediate laser beam 113 passes through the opening S is equal to or greater than h5 / Ds and equal to or less than h4 / Ds. The height at which the intermediate laser beam 113 passes through the final lens surface Sn is equal to or greater than h10 / Dn and equal to or less than h9 / Dn.

[0087] A specific numerical example is as follows: h1 / Ds=1.92×10 -2 h2 / Ds=1.00 h3 / Ds=9.81×10 -1 h4 / Ds=5.10×10 -1 h5 / Ds=4.90×10 -1 h6 / Dn=1.10×10 -2 h7 / Dn=8.59×10 -1 h8 / Dn=8.33×10 -1 h9 / Dn=3.18×10 -1 h10 / Dn=3.027×10 -1

[0088] <Action and effect of projection lens 3> Next, the function and effect of the projection lens 3 will be described.

[0089] When an illumination device is configured to include an array light source such as an LED array and a projection lens, it is possible to adjust the illumination area and illumination direction, and generate projection light in various patterns such as staggered or striped, by switching each light source in the array light source on or off, or by controlling the light intensity of the emitted light.

[0090] However, in such lighting devices, it is not possible to completely eliminate the spacing between light sources in the array light source, and therefore uneven light intensity may occur in the projected light due to dark lines or the like corresponding to the spacing between the light sources.

[0091] A configuration has been disclosed in which the image of a light source formed by a projection lens is intentionally defocused in order to suppress unevenness in the light intensity of the projected light. However, with the disclosed configuration, unevenness in light intensity may not be sufficiently suppressed due to the distribution (spread) of the point image, such as the point image having a convex light intensity distribution. Furthermore, if the amount of defocus is increased in order to sufficiently suppress unevenness in light intensity, the brightness contrast of the projected light caused by switching the light source on or off may not be sufficiently obtained, which may hinder the function of adjusting the illumination area and illumination direction and the function of generating projection light of various patterns.

[0092] In this embodiment, the projection lens is configured so that, of the light projected by the projection lens, central light that passes through the center of an opening included in the projection lens and peripheral light that passes through the periphery of the opening reach the same position on the image plane of the projection lens.

[0093] This configuration makes it possible to flatten the light intensity distribution of point images formed on the image plane by light emitted from each point of the light source (exit surface), and to make the image of the light source (exit surface image) formed by the aggregation of point images on the image plane into a predetermined state. As a result, it is possible to suppress the decrease in light intensity between adjacent exit surface images and to suppress uneven light intensity caused by dark lines corresponding to the spacing between multiple light sources. It is also possible to ensure the brightness contrast of the projected light when the light source is switched on or off.

[0094] For example, when an LED array is used as an array light source, the LED has a Lambertian light distribution characteristic, so the point image tends to have a convex light intensity distribution. In contrast, in this embodiment, the above configuration makes it possible to flatten the light intensity distribution of the point image. Therefore, application of this embodiment is particularly suitable when an LED array is used as an array light source.

[0095] Furthermore, in order to suppress unevenness in the light intensity of the projected light by the projection lens, in addition to the condition that the central light and peripheral light reach the same positions on the image plane Im, it is most preferable to satisfy the following conditions (A) to (C): (A) The transverse aberration has a sinusoidal shape. (B) Both the central light and the peripheral light reach the position where the central axis of the projection lens intersects with the image plane. (C) Within a plane including the central axis of the projection lens, the intermediate light reaches the position farthest from the positions on the image plane where the central light and peripheral light reach.

[0096] However, as long as the central light and the peripheral light reach the same positions on the image plane, it is not necessary to satisfy all of the above conditions (A) to (C). For example, even if the central light and the peripheral light reach positions other than the position where the central axis of the projection lens intersects the image plane, the same effects as those of the projection lens according to this embodiment can be obtained. Furthermore, even if the shape of the lateral aberration of the projection lens is other than a triangular wave shape, the same effects as those of the projection lens according to this embodiment can be obtained. Furthermore, even if the intermediate light reaches a position on the image plane other than the position farthest from the position where the central light and the peripheral light reach within a plane including the central axis of the projection lens, the same effects as those of the projection lens according to this embodiment can be obtained.

[0097] <Comparison with the lighting device described in Patent Document 1> Here, a comparison with the illumination device 100Y described in Patent Document 1 will be described. Fig. 12 is a diagram illustrating the characteristics of the illumination device 100Y described in Patent Document 1, and is a diagram of lateral aberration of the projection lens of the illumination device 100Y obtained by ray tracing simulation according to the conditions described in Patent Document 1. Fig. 12 can be viewed in the same way as the lateral aberration diagram in Fig. 7.

[0098] As shown in FIG. 12, the central ray, which has a diameter that is 10% or less of the diameter of the opening S, reaches a position near 0 on the image plane. On the other hand, the peripheral ray, which has a radial width that is 10% or less of the diameter of the opening, does not reach a position near 0 on the image plane, and does not reach a position where it overlaps with the central ray. Note that the position where the peripheral ray reaches on the image plane when the light passing position in the opening is 1.0 is 0.4 mm, and the positional deviation Δh between the central ray and the peripheral ray on the image plane Y is 0.4 mm.

[0099] In this way, with the illumination device 100Y, the central light and the peripheral light do not reach the same position on the image plane, and therefore it is not possible to obtain the same effects as with the illumination device 100 according to this embodiment.

[0100] [Variations] Next, we will explain a lighting device according to a modified example. In this modified example, the relationship between the area of the exit surface image on the image surface and the area of the point image formed on the image surface by light emitted from a specified point on the exit surface is specified, thereby further suppressing unevenness in the light intensity of the projected light.

[0101] Fig. 13 shows examples of the relationship between the area of the exit surface image and the area of the point image formed by the projection lens according to this modified example. Fig. 13(a) is a first example, Fig. 13(b) is a second example, and Fig. 13(c) is a third example. The first to third examples show three relationships for further suppressing unevenness in the light intensity of the projected light, and by configuring the projection lens to satisfy any one of the three relationships, it is possible to further suppress unevenness in the light intensity of the projected light.

[0102] 13(a) to 13(c), the diagrams shown on the left side show the relationship between the point image 131 near the center of the exit plane image and the exit plane image 132. An overlapping region 133 shown with matte hatching is the region where the point image 131 and the exit plane image 132 overlap.

[0103] 13(a) to 13(c), the diagrams on the right side show the relationship between the point image 131 and the exit plane image 132 near the gap between adjacent exit plane images. An overlapping region 133 shown with matte hatching is the region where the point image 131 and the exit plane image 132 overlap. The length L shown in FIG. 13 indicates the length of one side of the rectangular exit plane image, and the radius r indicates the radius of the point image.

[0104] As shown in FIG. 13(a), in the first example, the projection lens satisfies the following expressions (1) to (3). 2×r≦L (1) Sc=π×r 2 ···(2) Sg=(θ-sinθ)×r 2 / twenty three) Here, Sc represents the area of the point image 131, Sg represents the overlapping area of the point image 131 and the exit plane image 132, and θ represents the central angle of the sector formed by the overlapping of the point image 131 and the exit plane image 132. The same symbols have the same meanings hereinafter.

[0105] The value obtained by Sg / Sc × 2 corresponds to the dark line contrast. By determining the radius r and length L so as to satisfy the relationships of the above equations (1) to (3), the dark line contrast value can be increased to suppress unevenness in light intensity, while ensuring the brightness contrast of the projected light when the light source is switched on or off.

[0106] Furthermore, as shown in FIG. 13(b), in the second example, the projection lens satisfies the following expressions (4) to (6). L<2×r≦L×√2 (4) Sc=r 2 ×{π-2×(θ-sinθ)} ···(5) Sg=(θ-sinθ)×r 2 / 2-L×{cos(θ×r / 2)-G / 2} ···(6) Here, G represents the interval between adjacent exit surface images 132. The operation is the same as in the first example.

[0107] Furthermore, as shown in FIG. 13(c), in the third example, the projection lens satisfies the following expressions (7) to (9). L×√2<2×r≦L+G (7) Sc=L 2 ···(8) Sg=(θ-sinθ)×r 2 / 2+L×{cos(θ×r / 2)-G / 2} ···(9) The effect is the same as in the first example.

[0108] In this way, this modified example defines the relationship between the area of the exit surface image on the image plane and the area of the point image, thereby making it possible to further suppress unevenness in the light intensity of the projected light.

[0109] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims. [Explanation of symbols]

[0110] 1 LED array (an example of an array light source) 11 LED (example of light source) 12 Injection surface 13 Non-injection area 2. Control section 3 Projection Lens 4 Lens barrel 101 Injection surface image 102 Dark Line Image 131 Point image 132 Exit surface image 300 center light 301 Upper marginal light (an example of marginal light) 302 Lower marginal light (an example of marginal light) 303 Medium Light A center axis S opening L2, L2, L3 lenses Im image plane

Claims

1. an array light source having a plurality of light sources; a projection lens that projects the light emitted by the array light source, the projection lens includes an aperture; the light source has a rectangular emission surface that emits light, Among the light projected by the projection lens, central light passing through the center of the opening and peripheral light passing through the peripheral edge of the opening reach the same position on the image plane of the projection lens, a point image formed on the image plane by light emitted from a point where the central axis of the projection lens intersects with the exit surface has a flat light intensity distribution; Among the light beams projected by the projection lens within a plane including a central axis of the projection lens, intermediate light beams passing through a point between the center and the peripheral edge of the opening reach a position on the image plane that is farthest from the positions at which the central light beam and the peripheral light beam reach, When the length of one side of the exit surface image on the image plane is L and the radius of the point image formed by light exiting a predetermined point on the exit surface is r, A lighting device in which the length L and the radius r are determined to satisfy any one of the following sets of equations (1) to (3), (4) to (6), or (7) to (9): 2 × r ≦ L (1) Sc=π×r ２ ・・・（２） Sg=(θ-sinθ)×r ２ / 2 ・・・（３） L<2×r≦L×√2 (4) Sc=r ２ ×{π-2×(θ-sinθ)} ・・・（５） Sg=(θ-sinθ)×r ２ / 2+L×{cos(θ×r / 2)-G / 2} ・・・（６） L×√2<2×r≦L+G...(7) Sc=L ２ ・・・（８） Sg=(θ-sinθ)×r ２ / 2+L×{cos(θ×r / 2)-G / 2} ・・・（９） (Sc represents the overlapping area of the point image and the exit plane image when the center of the point image is located at the center of the exit plane image, Sg represents the overlapping area of the point image and the exit plane image when the center of the point image is located at the center between adjacent exit plane images, θ represents the central angle of the sector formed by the overlapping of the point image and the exit plane image, and G represents the distance between adjacent exit plane images.)

2. The illumination device according to claim 1 , wherein the peripheral light and the central light reach a position on the image plane where a central axis of the projection lens intersects with the image plane.

Images