JP2022053298A - Projection lens and illumination device - Google Patents

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

The present disclosure relates to projection lenses and illuminating devices.

A projection lens that projects light emitted by an array light source having a plurality of light sources is known. In such a projection lens, light intensity unevenness corresponding to the distance between a plurality of light sources may occur in the projected light.

Further, in order to suppress unevenness in the light intensity of the projected light, a configuration is disclosed in which the image of the light source by the projection lens is defocused (see, for example, Patent Document 1).

International Publication No. 2016/158886

However, with the configuration of Patent Document 1, it may not be possible to suppress unevenness in the light intensity of the projected light.

Therefore, it is an object of the present disclosure to provide a projection lens capable of suppressing unevenness in light intensity of projected light.

The projection lens according to the embodiment of the present disclosure is a projection lens that projects light emitted by an array light source having a plurality of light sources, includes an opening, and is the opening of the light projected by the projection lens. The central light passing through the center of the portion and the peripheral light passing through the peripheral edge of the opening reach the same position on the image plane of the projection lens.

The lighting device according to another embodiment of the present disclosure includes an array light source having a plurality of light sources and the projection lens.

According to the present disclosure, it is possible to provide a projection lens capable of suppressing unevenness in light intensity of projected light.

It is a figure which shows the structural example of the lighting apparatus which concerns on embodiment. It is a figure which shows the structural example of the LED array which concerns on embodiment. It is a figure which shows the light intensity unevenness reduction characteristic by the difference of the point image which constitutes an image, FIG. An ejection surface image composed of a point image (a point image having a distribution), FIG. 3C shows an adjacent ejection surface image. It is a figure of the aggregate example of the distribution point image, FIG. 4 (a) is a flat profile point image, FIG. 4 (b) is a convex profile point image, FIG. 4 (c) is a concave profile point image, and FIG. 4 (d). Shows an ejection plane image profile consisting of each point image. It is a light intensity distribution map of an adjacent emission plane image, FIG. 5A is a flat profile point image, FIG. 5B is a convex profile point image, and FIG. 5C is a concave profile point image. Shown by. It is a figure which shows the characteristic example of a projection lens, FIG. 6 (a) is a ray trajectory by a general projection lens, FIG. 6 (b) is the image plane light intensity distribution of FIG. 6 (a), and FIG. 6 (c) is. The ray trajectory by the projection lens according to the embodiment, FIG. 6 (d) shows the image plane light intensity distribution of FIG. 6 (c). It is a lateral aberration diagram of the projection lens which concerns on embodiment. It is a figure of the simulation result example of the lateral aberration of the projection lens for each angle of view on the object side, and FIGS. 8 (a) to 8 (e) show the lateral aberration at each point from the central axis of the projection lens to the maximum height. show. It is a figure which shows the misalignment allowable range of a central light and a limb darkening. 10A is a diagram illustrating an example of the projected light, FIG. 10A shows a photographed image of the projected light according to a comparative example, and FIG. 10B shows a photographed image of the projected light according to the embodiment. It is a figure which shows the example of the passing height of light in the opening of a projection lens and the final lens surface. It is a lateral aberration diagram of the projection lens described in Patent Document 1. It is a figure which shows the relationship example of the area of the ejection surface image by the projection lens which concerns on the modification, and the area of a distribution point image, FIG. c) is the third example.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the following description, the parts having the same reference numerals appearing in a plurality of drawings indicate the same or equivalent parts or members, and overlapping description will be omitted as appropriate.

Further, the embodiments shown below exemplify a projection lens and a lighting device for embodying the technical idea of the present invention, and the present invention is not limited to the embodiments shown below. The dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention to the specific description, but are intended to be exemplified. It is a thing. In addition, the size and positional relationship of the members shown in the drawings may be exaggerated in order to clarify the explanation.

The projection lens according to the embodiment is a projection lens that projects light emitted by an array light source having a plurality of light sources. In the embodiment, among the light projected by the projection lens, the central light passing through the center of the opening included in the projection lens and the peripheral light passing through the peripheral edge of the opening are equal on the image plane of the projection lens. The projection lens is configured to reach the position. With this configuration, the image of the light source by the projection lens is brought into a predetermined state on the image plane, and the light intensity unevenness corresponding to the distance between the plurality of light sources in the array light source is suppressed.

Hereinafter, an embodiment will be described by taking a lighting device having a projection lens as an example. In the figure shown below, the direction may be indicated by the X-axis, Y-axis, and Z-axis, but the X-direction along the X-axis is within the array plane in which a plurality of light sources are arranged in the array light source of the lighting device. Indicates a predetermined direction of. Further, the Y direction along the Y axis indicates a direction orthogonal to the X direction in the arrangement plane, and the Z direction along the Z axis indicates a direction orthogonal to the arrangement plane.

The direction in which the arrow points in the X direction is referred to as the + X direction, the opposite direction in 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 opposite direction in the + Y direction is referred to as the -Y direction. Notated, 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 is assumed to emit light in the + Z direction as an example. This does not limit the orientation of the projection lens and the illuminator when used, and the orientation of the projection lens and the illuminator is arbitrary.

[Embodiment]
<Configuration example of lighting device 100>
First, the configuration of the lighting device 100 according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram illustrating an example of the configuration of the lighting device 100. As shown in FIG. 1, the lighting device 100 includes 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 according to the drive voltage from the control unit 2. The projection lens 3 projects the light emitted by the LED array 1 onto the image plane Im.

The lighting device 100 illuminates or projects in, for example, an indoor lighting device, a device for illuminating walls inside and outside the building for space production, an in-vehicle lighting device such as a head lamp or a communication lamp, and a display device such as a projector. It is a device to perform.

The image plane Im is a plane that is conjugate with the light emission plane in the LED array 1 via the projection lens 3. When the lighting device 100 is used for lighting a wall surface, lighting for a display device, or projection, the image plane Im corresponds to a light projected surface such as a wall surface. Further, when the lighting device 100 is used for indoor lighting or an in-vehicle headlight, the image plane Im corresponds to a virtual plane in the space. It should be noted that this virtual plane includes a virtual plane corresponding to infinity. Further, when used for an in-vehicle communication lamp, the image plane Im corresponds to the road surface.

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

The LED array 1 is an example of an array light source having a plurality of LEDs, and the LED is an example of a light source. In the LED array 1, a plurality of LEDs are arranged in an array plane (in an XY plane) at substantially equal intervals. Each LED is electrically connected to the control unit 2 via a cable or the like, and by applying a drive voltage from the control unit 2, each LED can independently emit light.

The light emitted by the LED array 1 is, for example, white light. However, the present invention is not limited to this, and monochromatic light may be used, and various types of white light such as light bulb color, neutral white color, and daylight color can be selected. The type of the array light source is not limited to the LED array, and an array light source can be configured by arranging a plurality of fluorescent lamps in an array or bundling a plurality of optical fibers in an array.

The projection lens 3 has a lens L1, a lens L2, and a lens L3. The projection lens 3 can convert the light emitted by the LED array 1 and incident on the projection lens 3 into the desired projection light emitted from the projection lens 3. Here, the conversion of light means changing the traveling direction of light, for example, changing the incident light to desired focused light, collimated light, or divergent light.

Each lens is fixed in the 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 directly fixed and held to the housing without the lens barrel 4.

Of the projection lenses 3, the lens L1 is a biconvex spherical lens having a positive refractive power (power). The lens L2 is a Meniscus aspherical lens having a negative refractive power. The lens L3 is a biconvex spherical lens having a positive refractive power. Each lens can be configured by appropriately selecting glass, plastic, or the like of various materials according to the intended use of the lighting device 100.

The central axis A shown by the alternate long and short dash 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. Further, the opening S is a part of the projection lens 3, and is a circular part of the projection lens 3 located in a plane substantially parallel to the arrangement plane. The opening S has a function of defining an effective region 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, and a cat's eye shape can be applied.

Of the light incident on the projection lens 3, the light that reaches the inside of the opening S (on the side of the central axis A) passes through the opening S and forms the projected light 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.

The portion of such an opening S is determined by a member such as an aperture diaphragm provided in the optical path of the projection lens 3. Alternatively, the portion of the opening S is determined by a light-shielding film or a reflective film formed on the lens surface so that light reaching the outside of the opening S cannot pass through. The portion of the opening S is determined by the shape of the lens surface that refracts or reflects light that reaches the outside of the opening S in a direction that cannot be emitted from the projection lens 3.

The projection lens 3 of FIG. 1 illustrates a configuration in which an opening S is provided on the + Z direction side of the lens L2. The central light 300 in FIG. 1 corresponds to the main light beam of the projection lens 3 and passes through the substantially center of the opening S. The upper peripheral light 301 is light that passes through the substantially peripheral edge of the projection lens 3 on the + Y direction side, and the lower peripheral edge light 302 is light that passes through the substantially peripheral edge of the projection lens 3 on the −Y direction side. The upper limb darkening 301 and the lower limb darkening 302 are examples of peripheral light passing through the peripheral edge of the opening S, respectively. FIG. 1 shows a central light 300, an upper limb darkening 301, and a lower limb darkening 302 in a plane (meriplane) including the central axis A. The plane including the central axis A corresponds to a plane parallel to the paper surface in FIG.

Here, the central light 300 refers to light that passes through a circular region having a diameter that is 10% or less of the diameter of the opening S at the center of the opening S. Further, the peripheral light including the upper peripheral light 301 and the lower peripheral light 302 passes through an annular region having a radial width that is 10% or less of the diameter of the opening S at the peripheral edge of the opening S. Point to. Since the circular opening S is illustrated in the present embodiment, the ratio of the central light and the peripheral light is shown based on the diameter of the opening S. However, when the opening S is not circular, the opening S is shown. The size according to the shape of is the standard. When the opening S is not circular, the limb darkening is not an annular shape but a light that passes through a band-shaped region corresponding to the shape of the opening S.

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

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

The specification values shown in Table 1 are examples, and the specification values of the projection lens 3 can be appropriately determined according to the intended use of the lighting device 100. Further, the number of lenses constituting the projection lens 3, the refractive power of each lens, the arrangement, the application of a spherical surface or an aspherical surface, etc. are not limited to those described in FIG. It is possible. The surface shape and surface spacing of each lens in the projection lens 3 are determined so as to realize the characteristics and functions described later according to the configuration and specifications of the projection lens 3.

The lateral aberration diagram shown below, the height at which the light beam passes through the lens surface, the arrival position on the image plane, and the like will be described on the premise of the back light ray tracking of FIG. That is, the case where a light ray is incident on the projection lens 3 from the image plane side will be described.

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

As shown in FIG. 2, the LED array 1 arranges a total of 25 LEDs 11 in the array plane, five in the X direction and five in the Y direction. The ejection surface 12 shown by a broken line inside each of the LEDs 11 indicates a region where light is emitted in each LED 11. The LED 11 emits light in the + Z direction from each emission surface 12. The number and arrangement of the LEDs 11 are not limited to this, and can be appropriately selected. The LEDs can also be arranged in a one-dimensional array.

Here, since the space between the emission surfaces 12 of each LED 11 cannot be completely eliminated in the array plane, no light is emitted between the adjacent emission surfaces 12 in the LED array 1 as shown in FIG. The emission region 13 is included.

Due to the presence of the non-ejection region 13, the light intensity of the light projected by the projection lens may decrease in the region corresponding to the image of the non-ejection region 13 on the image plane Im (see FIG. 1), resulting in uneven light intensity. .. The region in which the light intensity of the projected light decreases corresponding to the image of the non-ejection region 13 is a dark linear region and is therefore referred to as a dark line.

In the present embodiment, the projection lens 3 is provided with a predetermined characteristic, and the image obtained by the projection lens 3 is brought into a predetermined state to suppress such unevenness in light intensity due to dark lines and the like. Hereinafter, predetermined characteristics of the projection lens 3 and a method for imparting the same will be described.

<Characteristics of projection lens 3 and example of application method thereof>
The characteristics of the projection lens 3 and the method of applying the projection lens 3 will be described with reference to FIGS. 3 to 8 and also with reference to the configuration diagram of FIG.

(Characteristics for reducing light intensity unevenness due to differences in point images)
First, FIG. 3 is a diagram for explaining the light intensity unevenness reduction characteristic due to the difference in the point images constituting the image. FIG. 3 (a) is a diagram showing an example of an injection surface image consisting of an ideal point image, FIG. 3 (b) is a diagram showing an example of an injection surface image consisting of a distribution point image, and FIG. 3 (c) is an adjacent injection surface. It is a figure which shows an example of an image. 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 point is the same when the graph showing the light intensity distribution is shown later. Here, the ideal point image means a point image having no distribution (spread), and the distributed point image means a point image having a distribution (spread).

The ideal emission surface image 31 of FIG. 3A shows an image of the LED emission surface of the LED array 1 by the projection lens 3, and is a plan view of the emission surface image in an ideal state on the image surface Im. The ideal profile 31p is the light intensity distribution of the AA cross section in the ideal ejection surface image 31. In the ideal profile 31p, the light intensity sharply increases in the region corresponding to the image of the ejection surface. Here, the profile means that the two-dimensional light intensity distribution of the luminous flux obtained in the cut plane when the luminous flux is cut in the plane orthogonal to the traveling direction of the luminous flux is further cut in the plane including the central axis of the luminous flux. This is the one-dimensional light intensity distribution obtained when the light intensity is distributed. Such a one-dimensional light intensity distribution can also be referred to as a cross-sectional light intensity distribution.

The distributed injection surface image 32 of FIG. 3B shows an image of the LED emission surface of the LED array 1 by the projection lens 3, and is a plan view of the emission surface image composed of the distribution point images on the image surface Im. .. The distribution profile 32p is the light intensity distribution of the BB cross section in the distributed injection surface image 32. The distributed emission surface image 32 is wider than the ideal emission surface image 31, and the light intensity of the distribution profile 32p gradually changes in the region corresponding to the end portion of the emission surface image.

FIG. 3 (c) shows an ideal profile 31p (dashed-dotted line) and a distribution profile 32p (dashed-dotted line) of two adjacent ejection surfaces. The light intensity drops sharply between the adjacent ideal profiles 31p, and the light intensity becomes almost zero. As a result, dark lines are generated with high contrast between adjacent ideal profiles 31p.

On the other hand, between the adjacent distribution profiles 32p, the light intensity does not decrease sharply, and the light intensity remains in both distribution profiles 32p. Therefore, the light intensities 33 are secured as shown in FIG. 3 (c) by adding the light intensities of both. As a result, the decrease in light intensity is alleviated between the adjacent distribution profiles 32p, and the contrast of dark lines is decreased. In other words, uneven light intensity due to dark lines and the like is suppressed. In the present embodiment, the light intensity unevenness reduction characteristic due to such a difference in point images is used.

(Example of forming an injection surface image by a set of distribution point images)
Next, FIG. 4 is a diagram illustrating an example of an aggregate of distribution point images. 4 (a) is a flat profile point image, FIG. 4 (b) is a convex profile point image, FIG. 4 (c) is a concave profile point image, and FIG. 4 (d) is an injection surface image profile consisting of each point image. show.

Here, the point image means an image formed by projecting light emitted from an arbitrary point in the LED emission surface of the LED array 1 onto the image surface Im by the projection lens 3. There are various distribution (spreading) states of point images, and FIGS. 4 (a) to 4 (c) show point images in different states.

FIG. 4A shows a distribution point image with a flat profile. The flat profile point image 41 in FIG. 4A is a plan 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.

The term "flat" in the terminology of the embodiment means light that becomes a peak in the two-dimensional light intensity distribution of the luminous flux obtained in the cut surface when the luminous flux is cut in a plane orthogonal to the traveling direction of the luminous flux. It means that the strength is spatially constant. Spatically constant means that the light intensities are equal at each position in the cut surface. However, "flatness" does not require that the spatial light intensity is completely constant (the light intensity at each position in the cut surface is completely the same), and is generally recognized as an error. Differences in light intensity are acceptable.

Regarding the evaluation method of whether or not the light intensity distribution is flat, for example, a luminous flux emitted from a point light source such as a pinhole arranged at a position corresponding to the emission surface of the LED array 1 is transferred to the image plane Im through the projection lens 3. Reach. When a light receiving element such as a CCD arranged at a position corresponding to the image plane Im receives a light beam, the PP (Peak to Peak) value of the brightness distribution of the light flux image (spot image) by the CCD is the luminance noise of the CCD. The profile can be said to be "flat" if:

For example, the PP value is acquired from the luminance distribution obtained by adding and averaging the luminance of each pixel in the spot image, and the luminance noise of the CCD is acquired by the standard deviation 3σ of the time variation of the luminance. By comparing the two, it can be determined whether or not the profile is "flat". Instead of the CCD, a measuring instrument such as a beam profiler may be used to receive the light beam, and based on the light reception result, it may be determined whether or not the profile is “flat”.

FIG. 4B is a diagram showing a convex profile point image in which the profile shape is convex. The convex profile point image 42 is a plan view of the distributed point image on the image plane Im, and the convex profile 42p is a profile of the DD cross section in the convex profile point image 42. In the convex profile point image 42, the light intensity increases toward the center.

FIG. 4C is a diagram showing a distribution point image in which the profile shape is concave. The concave profile point image 43 is a plan view of the distributed point image on the image plane Im, and the concave profile 43p is a profile of the EE cross section in the concave profile point image 43. In the concave profile point image 43, the light intensity decreases toward the center.

Here, a plurality of point images generated by the light emitted from each point in the LED emission surface are aggregated on the image surface Im to form an emission surface image. FIG. 4D shows a profile of an emission surface image in which a plurality of distribution point images corresponding to a plurality of points in one LED emission surface in the LED array 1 are aggregated on the image surface Im.

The flat injection surface profile 41com in FIG. 4D shows an injection surface profile in which a plurality of flat profile point images 41 are aggregated on the image surface Im. The convex injection surface profile 42com shows an injection surface profile in which a plurality of convex profile point images 42 are aggregated on the image surface Im. The concave injection surface profile 43com shows an injection surface profile in which a plurality of concave profile point images 43 are aggregated on the image surface Im.

As shown in FIG. 4 (d), the injection surface profile is different due to the difference in the distribution state. Therefore, it can be seen that the injection surface profile can be controlled by setting the distribution to a predetermined state. Further, the slope portion 41c in the profile distribution of the flat injection surface profile 41com has a more linear shape as compared with the slope portion 42c of the convex injection surface profile 42com and the slope portion 43c of the concave injection surface profile 43com.

(Example of relationship between distribution characteristics and light intensity between adjacent injection plane images)
Next, FIG. 5 is a diagram illustrating an example of the light intensity distribution of two adjacent emission plane images. 5 (a) is based on a flat profile point image, FIG. 5 (b) is based on a convex profile point image, and FIG. 5 (c) is based on a concave profile point image.

The light intensity 51 between the injection surface profiles 51a and 51b in FIG. 5A is larger than the light intensity 52 between the injection surface profiles 52a and 52b in FIG. 5B. Further, inflection points are observed in the distribution of the light intensity 53 between the injection surface profiles 53a and 53b in FIG. 5C, and the light intensity unevenness is conspicuous.

Therefore, by forming the injection surface profile with the flat profile point image having the flat light intensity distribution shown in FIG. 5 (a), the point image having the convex or concave light intensity distribution is adjacent to the point image. It is possible to suppress the decrease in light intensity between the emission surface images with respect to the peak light intensity of each emission surface image, and to suitably suppress the unevenness of light intensity due to dark lines and the like.

(Example of flattening the light intensity distribution of the distribution point image)
Next, the characteristics of the projection lens 3 for flattening the light intensity distribution of the distribution point image will be described. 6A and 6B are views for explaining an example of projection lens characteristics, FIG. 6A shows a ray trajectory by a general projection lens 3X, and FIG. 6B shows an image plane light intensity distribution of FIG. 6A. FIG. 6 (c) shows the ray trajectory by the projection lens 3 according to the present embodiment, and FIG. 6 (d) shows the image plane light intensity distribution according to FIG. 6 (c).

The projection lenses in FIGS. 6 (a) and 6 (c) are simplified and displayed as one lens in order to simplify the figure. Further, the components having the same function in FIGS. 6 (a) and 6 (c) are assigned the same part number (part symbol).

As shown in FIG. 6A, the projection lens 3X collects the light projected by the projection lens in the −Z direction side from the image plane Im regardless of the height (incident height) passing through the opening S. A distribution is given to the point image by condensing the light on the light point 5X. The distribution point image in this case has a convex profile as shown in FIG. 6 (b).

On the other hand, as shown in FIG. 6C, the projection lens 3 causes the central light 300 and the upper limb darkening 301 of the light projected by the projection lens 3 to reach the same position h0 on the image plane Im. As a result, a predetermined distribution characteristic is imparted to the point image.

Further, the projection lens 3 transmits the intermediate light 303, which passes between the peripheral edge and the center of the opening S, among the light projected by the projection lens 3 in the plane including the central axis A, as the central light on the image plane Im. The position hmax farthest from the arrival position of the 300 and the upper peripheral light 301 is reached. This also imparts a predetermined distribution characteristic to the point image.

By doing so, the light rays from the center to the middle and the light rays from the middle to the periphery in the opening S overlap each other, and as shown in FIG. 6D, the distribution point image by the projection lens 3 has a flat light intensity distribution. Has. For example, the distribution point image formed on the image plane Im by the light emitted at the point where the central axis A of the projection lens 3 intersects the emission plane of the LED array 1 can have a flat light intensity distribution.

Next, FIG. 7 is a lateral aberration diagram of the projection lens 3. The horizontal axis indicates the passing position of the light projected by the projection lens 3 in the opening S, and is standardized and displayed according to the maximum distance from the central axis A. 0 on the horizontal axis corresponds to the center of the opening S, and 1.0 corresponds to the peripheral edge of the opening S. The vertical axis indicates the arrival position of the light projected by the projection lens 3 on the image plane Im.

As shown in FIG. 7, the lateral aberration of the projection lens 3 has a sinusoidal shape. Specifically, the light passing through the center of the opening S, that is, the central light 300 in which the passing position of the light in the opening S is 0 reaches the position h0 on the image plane Im. Further, the light passing through the peripheral edge of the opening S, that is, the upper peripheral light 301 whose passing position of the light in the opening S is 1.0 reaches the position h0 at the image plane Im. Therefore, the arrival positions of the central light 300 and the upper limb darkening 301 on the image plane Im are the same.

Further, in the plane including the central axis A, the light passing between the center and the peripheral edge of the opening S, that is, the intermediate light 303 in which the passing position of the light in the opening S is 0.5 (see FIG. 6 (c)). ) Reach the position hmax at the image plane Im.

In the design of the projection lens 3, for example, the number of lenses, the material of each lens, and the specification values such as the focal length, Fno, and back focus are determined according to the specification application of the lighting device 100. Then, as an example, the arrival positions of the above-mentioned central light 300, upper peripheral light 301, and intermediate light 303 on the image plane Im are set as target values, and the shape of each lens surface of the projection lens 3 in the ray tracing simulation. And, the arithmetic processing for converging to the target value is executed with the surface spacing as a variable. This makes it possible to design a projection lens 3 for determining the optimum value of the shape and surface spacing of each lens surface in the projection lens 3 and flattening the light intensity distribution of the distribution point image.

<Examples of various data of the lighting device 100>
Next, as various data of the lighting device 100, a simulation result of the lateral aberration of the projection lens 3 and a shooting result of the projected light will be described.

(Example of lateral aberration simulation result)
FIG. 8 is a diagram showing an example of a simulation result of the lateral aberration of the projection lens 3 for each angle of view on the object side. 8 (a) shows the object side angle of view of 0 degrees, FIG. 8 (b) shows the object side angle of view of 4.3 degrees, and FIG. 8 (c) shows the object side angle of view of 9.6 degrees. In this case, FIG. 8D shows a case where the angle of view on the object side is 14.4 degrees, and FIG. 8E shows a case where the angle of view on the object side is 18.2 degrees. Further, FIGS. 8A to 8E show lateral aberrations in the X direction (graph on the right side) and the Y direction (graph on the left side), respectively.

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

Here, it may be difficult to completely match the positions of the central light 300 and the upper peripheral light 301 on the image plane Im due to manufacturing errors such as a shape error and an assembly error of the projection lens 3. On the other hand, even if the positions of the central light 300 and the upper limb darkening 301 on the image plane Im are not completely matched, if the positional deviation is within the permissible range, the same effect as in the case of matching can be obtained. There is.

Here, FIG. 9 shows an example of a simulation result for explaining the allowable range of the positional deviation between the central light 300 and the upper limb darkening 301 on the image plane Im. The view of FIG. 9 is the same as that of FIG. According to this simulation, the allowable range of the positional deviation Δh on the image plane Im of the central light 300 and the upper peripheral light 301 in the projection lens 3 is, for example, 0.07 mm or less.

A circular central light 300 having a diameter of 10% or less of the diameter of the opening S and a circular having a radial width of 10% or less of the diameter of the opening S and including the upper peripheral light 301. If the annular peripheral light overlaps at the image plane position even a little, it can be said that the central light 300 and the upper peripheral light 301 reach the same position on the image plane of the projection lens. Even in the central light and peripheral light at each angle of view on the object side shown in FIG. 8, the circular central light having a diameter of 10% or less of the diameter of the opening S and the central light having a diameter of 10% or less of the diameter of the opening S are used. Circular peripheral light having a certain radial width overlaps at least a part at the image plane position. When the shape of the opening S is not circular, the limb darkening is not an annular shape but a band-shaped region corresponding to the shape of the opening S.

(Example of projected light)
Next, FIG. 10 is a diagram illustrating an example of the projected light. FIG. 10A is a photographed image of the projected light on the image plane by the lighting device 100X according to the comparative example, and FIG. 10B is a photographed image of the projected light on the image plane by the lighting device 100 according to the present embodiment. Is shown. A comparative example is the projected light on the image plane by the lighting device 100X that does not impart a predetermined distribution characteristic. The captured image means an image captured by a camera of a projected image obtained when the projected light is projected onto a projected surface such as a screen.

As shown in FIG. 10A, in the lighting device 100X, the dark line image 102 is visually recognized between the adjacent emission 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 and the average light intensity Ip in the image area other than the dark line image 102, is 84% in the light projected by the illuminating device 100X. It became. Further, in the lighting device 100X, when the distribution characteristic by defocus was given, the dark line contrast was 91%. It should be noted that the larger the value of the dark line contrast, the lower the contrast of the dark line, and the more the unevenness of the light intensity is suppressed.

On the other hand, as shown in FIG. 10B, in the lighting device 100, the dark line and the LED image were hardly visually recognized, and the dark line contrast in the light projected by the lighting device 100 was 97%. The unevenness of light intensity is satisfactorily suppressed, and the projected light having a uniform light intensity is obtained as compared with the projected light by the lighting device 100X.

(Example of light passing height at the opening S and the final lens surface Sn in the projection lens 3)
Next, in order to express the characteristics of the projection lens 3, the height (position in the Y direction) through which the light incident on the projection lens 3 passes through the opening S and the height 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.

FIG. 11 shows the behavior when a laser beam having a beam diameter of about 0.5 mm, which is substantially parallel light, is incident on the projection lens 3 in a plane including the central axis A. Further, in FIG. 11, the projection lens 3 is simply displayed only on the first lens surface S1, the opening S, and the final lens surface Sn. Further, the radius Ds in FIG. 11 represents the radius of the opening S, and the radius Dn represents the radius of the final lens surface Sn.

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

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 0 or more and h1 / Ds or less. The height at which the central laser beam 111 passes through the final lens surface Sn is 0 or more and h6 / Dn or less.

The peripheral laser beam 112 is light that passes through the peripheral edge of the opening S. The peripheral laser beam 112 passes through a height of h3 or more and h2 or less at the opening S, and passes through a height of h8 or more and h7 or less at the final lens surface Sn.

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 h3 / Ds or more and h2 / Ds or less. The height at which the peripheral laser beam 112 passes through the final lens surface Sn is h8 / Dn or more and h7 / Dn or less.

The intermediate laser beam 113 is light that passes between the center and the peripheral edge 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.

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 h5 / Ds or more and h4 / Ds or less. The height at which the intermediate laser beam 113 passes through the final lens surface Sn is h10 / Dn or more and h9 / Dn or less.

Specific numerical examples are 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

<Action and effect of projection lens 3>
Next, the action and effect of the projection lens 3 will be described.

When an illumination device is configured including an array light source such as an LED array and a projection lens, the illumination area and illumination direction can be adjusted by switching on or off of each light source in the array light source, controlling the light intensity of the emitted light, and the like. Or, it is possible to generate various patterns of projected light such as staggered lights and stripes.

However, in such a lighting device, since the distance between the light sources in the array light source cannot be completely eliminated, the projected light may have uneven light intensity due to a dark line or the like corresponding to the light source distance.

A configuration is disclosed in which an image of a light source by a projection lens is intentionally defocused in order to suppress unevenness in the light intensity of the projected light. However, in the disclosed configuration, the light intensity unevenness may not be sufficiently suppressed due to the distribution (spreading) of the point image such that the point image has a convex light intensity distribution. In addition, if the amount of defocus is increased in order to sufficiently suppress uneven light intensity, the contrast between light and dark of the projected light due to switching of the light source on or off cannot be sufficiently obtained, and the function of adjusting the illumination area and the illumination direction can be obtained. , May interfere with the projected light generation function of various patterns.

In the present embodiment, among the light projected by the projection lens, the central light passing through the center of the opening included in the projection lens and the peripheral light passing through the peripheral edge of the opening are on the image plane of the projection lens. The projection lens is configured to reach the same position.

With this configuration, the light intensity distribution of the point image formed on the image surface by the light emitted from each point of the light source (emission surface) can be flattened, and the light source formed by collecting the point images on the image surface. Image (ejection surface image) can be in a predetermined state. As a result, it is possible to suppress a decrease in light intensity between adjacent emission plane images and suppress unevenness in light intensity due to dark lines or the like corresponding to the spacing between a plurality of light sources. In addition, it is possible to secure the contrast between light and dark of the projected light when the light source is switched on or off.

For example, when an LED array is used as an array light source, the LED has a Lambersian type light distribution characteristic, so that the point image tends to have a convex light intensity distribution. On the other hand, in the present embodiment, the light intensity distribution of the point image can be flattened by the above configuration. Therefore, when an LED array is used as the array light source, the application of this embodiment is particularly suitable.

Further, in order to suppress unevenness in the light intensity of the projected light by the projection lens, in addition to the condition that the arrival positions of the central light and the peripheral light on the image plane Im are the same, the following conditions (A) to (C) are satisfied. Satisfaction is most preferred.
(A) The lateral aberration has a sinusoidal shape.
(B) Both the central light and the limb darkening reach the position where the central axis of the projection lens intersects the image plane.
(C) In the plane including the central axis of the projection lens, the intermediate light reaches the position farthest from the arrival positions of the central light and the limb darkening on the image plane.

However, if the arrival positions of the central light and the limb light on the image plane are equal, it is not always necessary to satisfy all of the above conditions (A) to (C). For example, even in a configuration in which the central light and the limb darkening reach a position other than the position where the central axis of the projection lens intersects the image plane, the same effect as that of the projection lens according to the present embodiment can be obtained. Further, even if the shape of the lateral aberration of the projection lens is another shape such as a triangular wave shape, the same effect as that of the projection lens according to the present embodiment can be obtained. Further, the present embodiment also relates to a configuration in which the intermediate light reaches a position other than the position farthest from the arrival positions of the central light and the peripheral light on the image plane in the plane including the central axis of the projection lens. It is possible to obtain the same effect as that of a projection lens.

<Comparison with the lighting device described in Patent Document 1>
Here, a comparison with the lighting device 100Y described in Patent Document 1 will be described. FIG. 12 is a diagram illustrating the characteristics of the lighting device 100Y described in Patent Document 1, and is a lateral aberration diagram of the projection lens of the lighting device 100Y obtained by a ray tracing simulation according to the conditions described in Patent Document 1. .. The view of FIG. 12 is the same as the lateral aberration diagram of FIG. 7.

As shown in FIG. 12, the central light having a diameter of 10% or less of the diameter of the opening S reaches a position near 0 on the image plane. On the other hand, the limb darkening having a width in the radial direction which is 10% or less of the diameter of the opening does not reach the vicinity of 0 on the image plane and does not reach the position where it overlaps with the central light. The arrival position of the peripheral light in the opening where the light passing position is 1.0 is 0.4 mm, and the positional deviation Δh _Y between the central light and the peripheral light on the image plane is 0.4 mm. Is.

As described above, in the lighting device 100Y, since the central light and the limb darkening do not reach the same position on the image plane, it is not possible to obtain the same effect as the lighting device 100 according to the present embodiment.

[Modification example]
Next, the lighting device according to the modified example will be described. In this modification, the light of the projected light is defined by defining the relationship between the area of the ejection surface image on the image plane and the area of the point image formed on the image plane by the light ejecting a predetermined point in the ejection surface. Further suppresses strength unevenness.

FIG. 13 is a diagram showing an example of the relationship between the area of the ejection surface image by the projection lens and the area of the point image according to this modification. 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 the light intensity unevenness of the projected light, and the projection lens is configured so as to satisfy any one of the three relationships. The light intensity unevenness of light can be further suppressed.

The figure shown on the left side in each of FIGS. 13 (a) to 13 (c) shows the relationship between the point image 131 and the injection surface image 132 near the center of the injection surface image. The overlapping region 133 shown by satin hatching is a region where the point image 131 and the ejection surface image 132 overlap.

Further, the figure shown on the right side in each of FIGS. 13 (a) to 13 (c) shows the relationship between the point image 131 and the injection surface image 132 in the vicinity between the adjacent injection surface images. The overlapping region 133 shown by satin hatching is a region where the point image 131 and the ejection surface image 132 overlap. The length L shown in FIG. 13 indicates the length of one side of the rectangular injection surface image, and the radius r indicates the radius of the point image.

As shown in FIG. 13A, in the first example, the projection lens satisfies the following equations (1) to (3).
2 × r ≦ L ・ ・ ・ (1)
Sc = π × r ² ... (2)
Sg = (θ-sinθ) × r ^2/2・ ・ ・ (3)
Here, Sc represents the area of the point image 131, Sg represents the overlapping area of the point image 131 and the ejection surface image 132, and θ is a fan shape formed by superimposing the point image 131 and the ejection surface image 132. Represents the central angle. The same symbols have the same meaning in the following.

The numerical value obtained by Sg / Sc × 2 corresponds to the dark line contrast. By determining the radius r and the length L so as to satisfy the relationship of the above equations (1) to (3), the value of the dark line contrast is increased to suppress the light intensity unevenness, and the light source is turned on or off. It is possible to secure the contrast between light and dark of the projected light due to the switching of the light source.

Further, as shown in FIG. 13B, in the second example, the projection lens satisfies the following equations (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 distance between adjacent ejection plane images 132. The action is the same as in the first example.

Further, as shown in FIG. 13 (c), in the third example, the projection lens satisfies the following equations (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 action is the same as in the first example.

As described above, by defining the relationship between the area of the ejection surface image on the image plane and the area of the point image according to this modification, it is possible to further suppress the light intensity unevenness of the projected light.

Although the preferred embodiments and the like have been described in detail above, they are not limited to the above-described embodiments and the like, and various modifications and substitutions are made to the above-mentioned embodiments and the like without departing from the scope described in the claims. Can be added.

1 LED array (an example of array light source)
11 LED (an example of a light source)
12 Ejection surface 13 Non-emission area 2 Control unit 3 Projection lens 4 Lens lens barrel 101 Ejection surface image 102 Dark line image 131 Point image 132 Ejection surface image 300 Center light 301 Upper peripheral light (an example of peripheral light)
302 Lower limb darkening (an example of limb darkening)
303 Intermediate light A Central axis S Aperture L2, L2, L3 Lens Im image plane

Claims (8)

A projection lens that projects light emitted by an array light source having multiple light sources.
Including the opening
Of the light projected by the projection lens, the central light passing through the center of the opening and the peripheral light passing through the peripheral edge of the opening reach equal positions on the image plane of the projection lens. Projection lens. The projection lens according to claim 1, wherein the limb darkening and the central light reach a position on the image plane where the central axis of the projection lens intersects the image plane. Of the light projected by the projection lens in the plane including the central axis of the projection lens, the intermediate light passing between the center and the peripheral edge of the opening is the central light and the central light on the image plane. The projection lens according to claim 1 or 2, wherein the projection lens reaches the position farthest from the arrival position of the peripheral light. The light source has an emission surface that emits light.
The point image formed on the image plane by the light emitted at the point where the central axis of the projection lens intersects the ejection surface is according to any one of claims 1 to 3, which has a flat light intensity distribution. Projection lens. The light source has a rectangular emission surface that emits light.
When the length of one side of the ejection surface image on the image plane is L and the radius of the point image formed on the image plane by the light emitted from the predetermined point in the ejection surface is r, the following The projection lens according to any one of claims 1 to 4, which satisfies the equations (1) to (3).
2 × r ≦ L ・ ・ ・ (1)
Sc = π × r ² ... (2)
Sg = (θ-sinθ) × r ^2/2・ ・ ・ (3)
(Sc represents the area of the point image, Sg represents the superposed area of the point image and the ejection surface image, and θ is the central angle of the fan shape formed by superimposing the point image and the ejection surface image. Represents.) The light source has a rectangular emission surface and has a rectangular emission surface.
When the length of one side of the ejection surface image on the image plane is L and the radius of the point image formed on the image plane by the light emitted from the predetermined point in the ejection surface is r, the following The projection lens according to any one of claims 1 to 4, which satisfies the equations (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)
(Sc represents the area of the point image, Sg represents the superposed area of the point image and the ejection surface image, and θ is the central angle of the fan shape formed by superimposing the point image and the ejection surface image. Represents, and G represents the distance between the adjacent ejection plane images.) The light source has a rectangular emission surface and has a rectangular emission surface.
When the length of one side of the ejection surface image on the image plane is L and the radius of the point image formed on the image plane by the light emitted from the predetermined point in the ejection surface is r, the following The projection lens according to any one of claims 1 to 4, which satisfies the equations (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)
(Sc represents the area of the point image, Sg represents the superposed area of the point image and the ejection surface image, and θ is the central angle of the fan shape formed by superimposing the point image and the ejection surface image. Represents, and G represents the distance between the adjacent ejection plane images.) An array light source with multiple light sources and
A lighting device comprising the projection lens according to any one of claims 1 to 7.

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