Lighting device for smart device

Abstract

[Problem] To provide a lighting device for a smart device, the lighting device being suitable for photographing with a camera by close-up photography at a short distance in an environment where the amount of light from outside is small.　[Solution] This lighting device for a smart device is attached externally to a smart device 200 having a function of photographing with a camera. This lighting device is provided with: a circle-shaped circular housing 110 provided with an inner peripheral wall surface 111, an outer peripheral wall surface 112, an upper surface, and a bottom surface 114; and a circular light source 120 having a plurality of LED elements 121 arranged on the bottom surface 114 of the circular housing 110. A light transmissive diffusion plate 113 is attached to the upper surface of the circular housing 110, and there is a hole 115 in the center of the circular light source 120. The circular light source 120 is attached so as to surround a camera lens 210 of the smart device 200 by mounting tools 130, 140 to be mounted to the smart device 200. Lighting and driving of the plurality of LED elements 121 are controlled using a switching control unit 160.

Description

Lighting devices for smart devices

[0001] The present invention relates to a lighting device including a light-emitting diode (LED). In particular, the present invention relates to a lighting device that is attached to surround the lens of a camera of a smart device such as a portable smartphone or tablet information terminal equipped with a camera function. The use of the smart device camera to which the lighting device of the present invention is applied is not limited.

[0002] In the prior art, smart devices such as smartphones and tablet information terminals are equipped with a camera photography function as a basic function. Photography using the camera photography function of a smart device is performed in a variety of scenes, and photography is also expected to be performed in conditions where there is insufficient external light, such as at night. Therefore, a prior art smart device camera has a pin lens in which tiny LED elements are arranged to surround the aperture of the pin lens, and the LED elements emit powerful light to provide flash illumination for the camera.

[0003] According to the technology disclosed in Patent Document 1 (JP 2021-182147 A: "LED Flash Ring Surrounding a Camera Lens"), a ring-shaped light guide is incorporated near the lens opening of a smart device, as shown in FIG. 15. A first LED is encapsulated by the molded light guide of the flash system, and a second LED is encapsulated at the opposite end of the light guide. The light guide emits light from the LEDs uniformly forward with a peak aligned with the axis of the lens opening, and is positioned so that it does not directly enter the camera's field of view.

[0004] Next, according to the technology disclosed in Patent Document 2 (JP 2019-512147 A: Title of the invention: "Uniform, efficient, and color-tunable ring flash for cameras using LEDs emitting light from multiple surfaces"), as shown in FIG. 16, there is provided a ring-shaped light guide including an LED having at least two perpendicular light-emitting side surfaces, a bottom surface, a top surface including the light-emitting surface, an inner sidewall, and an outer sidewall defining a recess having at least two perpendicular coupling surfaces that fit into the at least two perpendicular light-emitting surfaces of the LED.

[0005] Japanese Patent Application Publication No. 2021-182147

[0006] The LED flash ring technology described above had some areas for improvement. Due to the constraints of having to place the LED elements immediately around the pin lens, the technology uses tiny point light sources arranged in a ring shape and controlled to irradiate a uniform ring-shaped light. However, as a point light source, the LED elements emit a momentary flash, similar to a camera strobe flash. While emitting a continuous flash for several seconds can be used to capture short videos at night or in places where external light is difficult to reach, this is not sufficient.

[0007] Furthermore, because the tiny LED elements are incorporated into a small area immediately around the pin lens, a highly optically transparent medium must be used to emit a strong flash of illumination light into the outside world, and the strong flash is emitted directly. Therefore, if the subject is close, the LED elements, which act as a point light source, emit a strong flash of light toward the subject. If a camera is used in an environment where this flash is emitted, the camera image will be reflected too strongly from the subject's surface, resulting in an unnatural image or video that differs from that captured using natural light. In other words, while camera photography using the LED flash ring of the above-mentioned prior art is suitable for photographing subjects from a sufficient distance, such as several meters to several tens of meters, it is not suitable for close-up photography at close distances of several centimeters or several tens of centimeters.

[0008] Although camera photography using an LED flash ring built into a smart device has problems when it comes to taking close-up shots in low-light environments as described above, the widespread use of smartphones and tablet information terminals has been remarkable, and many people are accustomed to using them. They are also affordable and easy to use, and have a wide range of data processing functions other than photography, so there are various advantages to being able to take close-up shots using a smart device even in low-light environments.

[0009] In order to solve the above problems, the present invention aims to provide a lighting device for smart devices that is suitable for close-up photography at a distance of a few centimeters or tens of centimeters in an environment where the amount of light from the outside world is low and illumination from an artificial light source is required.

[0010] The present invention provides a lighting device for a smart device that is externally attached to a smart device equipped with a camera function, the lighting device comprising: a circular housing having an inner peripheral wall surface, an outer peripheral wall surface, a bottom surface, and a top surface; a circumferential light source having a plurality of LED elements arranged on the bottom surface of the circumferential housing; a circumferential light source having a light-transmitting and light-diffusing diffusion plate attached to the top surface of the circumferential housing; and a mounting fixture for mounting the circumferential light source on the smart device so as to surround the camera lens of the smart device. Here, the smart device is a smartphone or a tablet-type information terminal.

[0011] According to the lighting device for smart devices configured as described above, a circular light source can be attached externally so as to surround the camera lens, making it possible to add a relatively large circular light source.Furthermore, since a translucent diffusion plate with translucency and light diffusion properties is arranged on the upper surface of the circular light source, the light emitted by the LED element, which is originally a point light source, can be appropriately diffused to create a gentle, large, circular lighting body.In environments where the amount of light from the outside world is low and illumination light from an artificial light source is required, a lighting device suitable for close-up photography with a camera at a distance of a few centimeters or a few tens of centimeters can be provided.

[0012] For example, if the outer shape of the surrounding housing of the orbiting light source is a circular or elliptical ring shape, a large, well-balanced, and gentle ring-shaped illumination body can be obtained. Furthermore, if the outer shape of the surrounding housing of the orbiting light source is a polygonal ring shape, a large, well-balanced, and gentle ring-shaped illumination body can be obtained. It is desirable that the inner surface of the surrounding housing, excluding the light-transmitting diffusion plate disposed on the upper surface of the orbiting light source, has a high reflectivity.

[0013] In the smart device lighting device having the above configuration, it is preferable that the distance H from the height at which the LED elements are disposed to the height of the light-transmitting diffusion plate on the upper surface and the distance W from the position at which the LED elements are disposed to the inner peripheral wall surface of the surrounding housing satisfy the condition of the following (Equation 6): 0.5W ≦ H ≦ 5.7W (Equation 6) This numerical range has the following technical significance.

[0014] Light emitted by LEDs has a strong tendency to travel in a straight line, and the intensity of the light weakens with each angle deviation from the straight line. With commonly used LEDs, the light intensity is halved when the emission angle is 60 degrees. Therefore, it is preferable that the emission angle of the LED light relative to the inner peripheral wall surface of the circular light source not exceed 60 degrees, as shown in Figure 8(c). In other words, the lower limit at which more than 50% of the luminous flux is irradiated onto the diffuser is 60 degrees. Expressing this condition in terms of the distance between the LED and the inner peripheral wall surface, W / H = tan 60, which results in H = 0.5W. Next, if the width of the circular housing of the circular light source (the distance between the inner peripheral wall surface and the outer peripheral wall surface) is narrow, the light will be concentrated in the straight line of the LED, making it difficult for the irradiated light to reach the surrounding area. Therefore, the width of the circular housing of the circular light source must also be considered. As shown in Figure 8(c), if the limit is an emission angle of 10 degrees for the LED light, and the relationship with each distance is described in the same way as above, W / H = tan 10°, and calculations based on this relationship result in H = 5.7 W. These conditions lead to the numerical range 0.5 W ≦ H ≦ 5.7 W.

[0015] Next, in the lighting device for a smart device having the above configuration, it is preferable that the height CH of the inner peripheral wall surface of the circumferential housing and the distance CW from the center of the camera lens of the smart device to the inner peripheral wall surface of the circumferential housing satisfy the condition of the following (Equation 7): 1 mm≦CH≦1.7CW (Equation 7).

[0016] This numerical range has the following technical significance. Smart devices often use wide-angle lenses for their camera lenses, with a field of view of approximately 60 degrees. Furthermore, since it is necessary to avoid the outer wall of the case being reflected within the field of view (field of view), this is considered the limit. This condition can be expressed as the distance relationship in the structure of the orbiting light source's circumferential housing, as shown in Figure 9(b), and calculations based on this relationship yield CH ≦ 1.7CW. Furthermore, in order to mount the circumferential light source externally so that it surrounds the lens, a certain height CH of the inner peripheral wall of the circumferential housing is necessary, so it is considered necessary to have a height of 1 mm or more. These conditions lead to the numerical range of 1 mm ≦ CH ≦ 1.7CW.

[0017] Next, we will describe a method for tilting the illumination direction of the LED element toward the center of the smart device's camera lens by an angle D that satisfies the condition of the following equation (8), thereby slightly converging the illumination direction toward the center. As shown in Figure 10, the inclination angle D is set to satisfy the condition of the following equation (8), so that the illumination direction of the LED element is tilted toward the center of the smart device's camera lens. (Equation 8) 0 ≦ D ≦ arctan (W + CW) / 300 mm As a structure for tilting the illumination direction of the LED element to satisfy the above condition, there is a structure in which the LED element is attached to the circuit board at a predetermined inclination angle so that it faces toward the center of the smart device's camera lens. Another structure is to tilt the arrangement of the light-transmitting diffusion plate on the top surface of the surrounding housing. Either structure can slightly converge the illumination direction of the LED element toward the center of the smart device's camera lens. By tilting the illumination direction of the LED element toward the center of the smart device's camera lens, the illumination light from the LED element is emitted while slightly converging toward the center. Since the subject is often located toward the center of the camera lens, the subject is likely to be brightly illuminated and the photographic conditions may be better.

[0018] Next, we will describe the LED driving method in the smart device lighting device of the present invention. To control the driving of the LEDs, a switching control unit is provided that performs switching control of the LED elements. This switching control unit is used to control the illumination of multiple LED elements. By incorporating a switching control unit, multiple LEDs can be turned on and off in various patterns. For example, the number of LED elements arranged in a surrounding housing can be four or more, and the LEDs can be divided into at least a first group and a second group for drive control. In other words, by dividing the LEDs into groups in this way, the switching control unit can control the illumination of the LED elements by switching between multiple patterns: a full illumination pattern in which the first and second groups of LED elements are illuminated; a first group illumination pattern in which the first group of LED elements is illuminated and the second group of LED elements is illuminated; and a second group illumination pattern in which the first group of LED elements is illuminated and the second group of LED elements is illuminated.

[0019] Furthermore, if the number of LEDs is large, the LED elements can be grouped into third and fourth groups in addition to the first and second groups. In this case, when the switching control unit controls the lighting of the LED elements, the full lighting pattern is a pattern in which all of the LED elements in groups 1 to 4 are lit. Furthermore, in addition to the first group lighting pattern and the second group lighting pattern described above, a third group lighting pattern in which the LED elements in groups 1, 2, and 4 are turned off and only the third group is lit, and a fourth group lighting pattern in which the LED elements in groups 1, 2, and 3 are turned off and only the fourth group is lit, etc. are also possible, thereby diversifying the illumination patterns.

[0020] Next, the driving control of the lighting of the LED elements by the switching control unit can also be devised. The first driving control is static driving control for the lighting of the LED elements. With this static driving control, the lit LEDs stay lit throughout their lighting period.

[0021] The second type of drive control is pulse drive control, which controls the lighting of the LED elements. This pulse drive control has various advantages, such as being able to emit a large amount of light with little power, suppressing heat generation from the LED, and reducing the burden on the circuit.

[0022] On the other hand, when taking camera photography into consideration, it is preferable to control the timing of the LED element pulse lighting and the timing of the video frame shooting by the camera photography function of the smart device to be synchronized. If they are not synchronized, and the timing of the video frame shooting by the camera photography function of the smart device overlaps with the timing of the LED element pulse lighting and turning off, frames shot in a dark state without LED illumination will be mixed in.

[0023] In old movie projectors, the timing of the frame advance of the film was synchronized with the on / off timing of the lighting device that illuminates from behind, so that so-called frame-by-frame images were displayed on the screen. Using a similar principle, if the timing of the video frame capture by the camera shooting function of a smart device is synchronized with the timing of the pulse-driven lighting of the LED elements, the frames of the video frame can be captured under conditions where they are always illuminated by the light from the LED elements.

[0024] In addition to a method in which the timing of capturing video frames using the camera photography function of a smart device is synchronized with the timing of pulse driving of the LED elements, if the LED elements are divided into multiple groups and their lighting is controlled using pulse driving, it is possible to control so that at least one of the first group of LED elements or the second group of LED elements is lit at any given time by shifting the timing of the pulse driving of the first group of LED elements and the timing of the pulse driving of the second group of LED elements.Even with a drive method in which the timing of lighting and extinguishing is shifted for each group, it is possible to capture video frames in a state where each frame is always illuminated by the LED elements of one of the groups.

[0025] Next, the range of the color temperature CT and the color rendering index Ra of the LED element can also be devised. The range of the color temperature CT of the LED element is preferably 4000K≦CT≦6500K, and the range of the color rendering index Ra of the LED element is preferably 90≦Ra<100. These numerical ranges provide LED illumination light that is ideal for photographing a variety of subjects.

[0026] The lighting device for smart devices of the present invention can be fitted with an external circumferential light source that surrounds the camera lens, and can add a relatively large circumferential light source. Furthermore, a light-transmitting diffusion plate with light-transmitting and light-diffusing properties is disposed on the upper surface of the circumferential light source, so that the light emitted by the LED element, which is essentially a point light source, can be appropriately diffused to create a gentle, large, circumferential lighting body. Even in environments where the amount of light from the outside world is low and illumination from an artificial light source is required, this lighting device is suitable for close-up photography with a camera at a distance of a few centimeters or a few tens of centimeters.

[0027] 1 is a perspective view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 2 is a front view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 3 is a rear view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 4 is a right side view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 5 is a left side view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 6 is a plan view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 7 is a bottom view showing a simplified structure of a smart device lighting device 100 according to Example 1 of the present invention; FIG. 8 is a diagram showing a preferred arrangement of an LED element 121 within the space of a surrounding casing 110; FIG. 9 is a vertical cross-sectional view showing the arrangement relationship between the height of an inner peripheral wall surface 111 of the surrounding casing 110, the inner diameter of the surrounding casing 110, and a camera lens 210; FIG. 10 is a diagram showing a simplified configuration when an inclination angle D is applied to the light emitted by an LED element 121 of a surrounding light source 120; and FIG. 11 is a diagram showing a simplified circuit configuration of a smart device lighting device 100. 1 is a diagram illustrating a first group lighting pattern and a second group lighting pattern. 2 is a diagram illustrating a lighting pattern when the LED elements 121 are divided into three groups. 3 is a diagram illustrating changes in supply current to each group in a pattern where the LED elements 121 are divided into three groups. 4 is a diagram simply illustrating an example of the configuration of a flash ring shown in Patent Document 1 (JP 2021-182147 A) in the prior art. 5 is a diagram simply illustrating an example of the configuration of a ring flash shown in Patent Document 2 (JP 2019-512147 A) in the prior art.

[0028] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a lighting device for a smart device according to the present invention will be described. Note that the following embodiment is merely an example and does not limit the technical scope of the present invention.

[0029] The smart device lighting device 100 of the present invention according to Example 1 is externally attached to a smart device equipped with a camera function. A basic version is shown below. FIGS. 1 to 7 are simplified diagrams illustrating the smart device lighting device 100 of the present invention according to Example 1. FIG. 1( a) is a perspective view of the smart device lighting device 100, and FIG. 1( b) is a perspective view showing the smart device lighting device 100 externally attached to a smart device 200. Similarly, FIG. 2 is a front view, FIG. 3 is a rear view, FIG. 4 is a right side view, FIG. 5 is a left side view, FIG. 6 is a plan view, and FIG. 7 is a bottom view. In each of the drawings, (a) shows only the smart device lighting device 100, and (b) shows the smart device lighting device 100 externally attached to a smart device 200.

[0030] As shown in FIGS. 1 to 7 , the lighting device 100 for smart devices includes a circumferential housing 110, a circumferential light source 120, a right wearing device 130, a left wearing device 140, and a main body 150.

[0031] The following describes each component in order. The circular housing 110 is a circular housing having an inner wall surface 111, an outer wall surface 112, a light-transmitting diffusion plate 113 attached to the top surface, a bottom surface 114, and a central hole 115.

[0032] The inner peripheral wall surface 111 is a wall surface that separates the inner peripheral side of the circumferential housing 110, and the hole that the inner peripheral wall surface 111 goes around is the central hole 115. Although the inner peripheral wall surface 111 is circular in this drawing, it may be circular, elliptical, or polygonal, and although it is basically a circumferential hole, it may also be a horseshoe shape with a partially sealed slit.

[0033] The outer peripheral wall surface 112 is a wall surface that separates the outer peripheral side of the orbiting housing 110, and the diameter of the orbiting outer peripheral wall surface 112 is the maximum diameter of the light source of the orbiting light source 120. Although the outer peripheral wall surface 112 is circular in this drawing, it may be circular, elliptical, or polygonal, and although it is basically orbiting, it may also be horseshoe-shaped with a sealed gap in part.

[0034] The light-transmitting diffusion plate 113 is a member attached in a circular shape to the upper surface of the circular housing 110 (that is, a portion separated by the inner peripheral wall surface 111 and the outer peripheral wall surface 112), and is made of a material that is light-transmitting and has light-diffusing properties. In other words, it is a material that transmits the irradiated light emitted from the LED elements 121 mounted inside and has light-diffusing properties. For example, it may be made of a milky white polycarbonate material, but this is not limited to this. Note that in this drawing, it has a concentric doughnut shape, but it may be a circle, ellipse, or polygon to match the inner peripheral wall surface 111 and the outer peripheral wall surface 112, and although it is basically a circular one, it may also be a horseshoe shape with a sealed slit in one part.

[0035] Bottom surface 114 is the bottom surface of circular housing 110 (i.e., the bottom surface of the circular space partitioned by inner peripheral wall surface 111 and outer peripheral wall surface 112). Although bottom surface 114 is a concentric donut shape in this drawing, it may be circular, elliptical, or polygonal to match inner peripheral wall surface 111 and outer peripheral wall surface 112, and although a circular shape is the basic shape, a horseshoe shape with a sealed slit in part may also be used. A substrate on which a plurality of LED elements 121 are arranged is attached on top of bottom surface 114, as will be described later.

[0036] The central hole 115 is a hole provided in the center of the orbiting light source 120. As shown in each of FIGS. 1(b) to 7(b), the orbiting light source 120 is externally attached to the smart device 200, and LED irradiation light is emitted forward from the orbiting light source 120. The hole 115 serves as a window, allowing the camera lens 210 of the smart device 200 to capture images of the area ahead. The LED irradiation light is emitted forward from the orbiting light source 120 so as to surround the camera lens 210 of the smart device 200, so that light reflected by an object in front passes through the hole 115 and can be received by the camera lens 210. The size of the central hole 115 is not limited, but may be any size as long as it is the same diameter as the camera lens 210 of the smart device 200, and may be, for example, approximately 2 cm to 7 cm.

[0037] The circulating light source 120 is a light source that emits irradiation light from a light-transmitting diffusion plate 123 attached to the upper surface of the circulating housing 120. As the light source of the circulating light source 120, a plurality of LED elements 121 (not shown in FIGS. 1 to 7 but shown in FIG. 8 and subsequent figures) are provided that are mounted in a circumferential pattern inside the circumferential housing 110. In this configuration example, as will be described later, eight LED elements 121 are mounted in the internal space of the circumferential housing 110.

[0038] The plurality of LED elements 121 may be light-emitting diodes, but are not limited thereto. Preferably, the LED elements meet the following specifications. The important factors required for the LED illumination light are: (1) durability for photography in low-light environments, (2) durability for photography in close-up mode where the subject is close, (3) absence of glare even when the subject is a white object, (4) ability to photograph the subject with high color reproducibility, and (5) uniform brightness of the subject. The following numerical ranges are set as the ranges of color temperature CT and color rendering index Ra of LED elements that satisfy the above conditions. The range of color temperature CT of the LED element is the range given by the following (Equation 9): (Equation 9) 4000K≦CT≦6500K The range of color rendering index Ra of the LED element is the range given by the following (Equation 10): (Equation 10) 90≦Ra<100

[0039] Next, a preferred arrangement of the LED elements 121 within the space of the surrounding housing 110 will be described. FIG. 8 is a diagram illustrating a preferred arrangement of the LED elements 121 within the space of the surrounding housing 110. FIGS. 8(a) and 8(b) are planar bird's-eye views of the arrangement of multiple LED elements 121 within the surrounding housing 110. In the configuration example of FIG. 8(a), the surrounding housing 110 has a circular outer shape, while in FIG. 8(b), the surrounding housing 110 has a polygonal outer shape (a regular dodecagon). In both cases, eight LED elements 121 are arranged in a circular pattern within the internal space of the surrounding housing 110. Note that the LED elements 121 do not need to be arranged at 45-degree intervals from the center point, as long as they are arranged approximately evenly in a circular pattern. In this example, there are four sets of two LED elements 121, and the sets are arranged symmetrically across the vertical or horizontal axis. In this example, the intervals are approximately 40 degrees (for example, the angle formed from the center by LED element 121-1 and LED element 121-2), and the intervals between each set (for example, the angle formed from the center by LED element 121-2 and LED element 121-3) are 50 degrees. Note that the lighting control and drive control of each LED element 121 will be described later.

[0040] Next, FIG. 8( c ) is a vertical cross-sectional view showing the arrangement of one LED element 121 within the surrounding housing 110. In the example of FIG. 8( c ), the wall surfaces of the surrounding housing are shown in cross-section, depicting the vertical cross-sections of the inner peripheral wall surface 111, the outer peripheral wall surface 112, the light-transmitting diffusion plate 113, and the bottom surface 114. One LED element 121 is disposed near the center on a circuit board 122. Note that the arrangement example of FIG. 8( c ) is merely an example, and the arrangement position of one LED element 121 in the surrounding direction (the arrangement position in the horizontal direction in the figure) and the arrangement height of the circuit board 122 (the arrangement position in the vertical direction in the figure) may be other positional relationships.

[0041] Here, the LED elements 121 are arranged so that the height H from the LED element 121 to the light-transmitting diffusion plate 113 and the distance W from the center of the arrangement position of the LED element 121 to the LED element 121 and the inner peripheral wall surface 111 satisfy the following (Equation 11): 0.5W≦H≦5.7W (Equation 11)

[0042] This numerical range has the following technical significance. First, let us consider the lower limit of (Equation 11). LED light has a strong tendency to travel in a straight line, and the intensity of the light weakens with each angle deviation from that straight line. With commonly used LEDs, the light intensity is halved when the emission angle is 60 degrees. Therefore, it is preferable that the emission angle of the LED light relative to the inner peripheral wall surface of the circular light source, as shown in Figure 8(c), does not exceed 60 degrees. In other words, 60 degrees is the lower limit at which 50% or more of the luminous flux is irradiated onto the diffuser plate. If this condition is expressed in terms of the relationship between the LED and the inner peripheral wall surface, W / H = tan 60, and if calculated based on this relationship, H = 0.5W.

[0043] Next, we will discuss the upper limit range of (Equation 11). If the width of the surrounding housing of the orbiting light source (the distance between the inner and outer peripheral wall surfaces) is narrow, the light will be concentrated in the straight direction of the LED, making it difficult for the irradiated light to reach the surrounding area. Therefore, the width of the surrounding housing of the orbiting light source must also be taken into consideration. As shown in Figure 8(c), if the LED's irradiated light emission angle is set to 10 degrees, and the relationship with each distance is described in the same way as above, W / H = tan 10°, and calculation based on this relationship results in H = 5.7W. Thus, the numerical range of 0.5W ≦ H ≦ 5.7W in (Equation 11) is derived.

[0044] Next, FIG. 9 is a vertical cross-sectional view showing the arrangement relationship between the height of the inner wall surface 111 of the circular housing 110, the inner diameter of the circular housing 110, and the camera lens 210 of the smart device 200. FIG. 9 depicts a vertical cross-section of the circular housing 110 and the smart device 200. Because the circular housing 110 is circular, the space of the circular housing 110 on the left side and the circular housing 110 on the right side are depicted. Between them is the central hole 115 of the circular housing 110. In FIG. 9( a), the smart device 200 is disposed below the circular housing 110, and the camera lens 210 is positioned in the center of the central hole 115 of the circular housing 110. In FIG. 9, it is preferable that the height CH of the inner wall surface of the circular housing 110 and the distance CW from the center of the camera lens 210 of the smart device to the inner wall surface 111 of the circular housing 110 satisfy the following condition (Equation 12). (Number 12) 1 mm ≦ CH ≦ 1.7 CW

[0045] This numerical range has the following technical significance. Figure 9(b) illustrates the height CH of the inner peripheral wall surface of the circumferential housing 110 and the distance CW from the center of the camera lens 210 of the smart device to the inner peripheral wall surface 111 of the circumferential housing 110 when the upper limit of (Equation 12) is reached. Wide-angle lenses are often used in smart devices, and many of these have an angle of view of approximately 60 degrees. Furthermore, the upper limit was set because it is necessary to prevent the outer wall of the case from being reflected in the angle of view (field of view). This condition can be expressed as the distance relationship in the circumferential housing structure of the circumferential light source, CW / CH = tan 30°, and calculations based on this relationship yield CH ≦ 1.7CW.

[0046] Next, regarding the lower limit, in order to externally attach the orbiting light source 120 so as to surround the camera lens 210, the height CH of the inner peripheral wall surface of the orbiting housing 110 needs to be at least 1 mm, and therefore it is considered necessary for the height CH to be at least 1 mm. From these conditions, the numerical range of 1 mm ≦ CH ≦ 1.7 CW is derived.

[0047] Next, we will discuss a method for slightly converging the illumination direction of the LED element 121 of the orbiting light source 120 toward the center of the smart device's camera lens. By tilting the illumination direction of the LED element toward the center of the smart device's camera lens, the light emitted by the LED element is emitted while slightly converging toward the center. Since the subject is often located toward the center of the camera lens, the subject is brightly illuminated, potentially improving the shooting conditions. We will now discuss the conditions for setting an inclination angle D in the illumination direction of the LED element 121. The condition for the inclination angle D is preferably expressed by the following equation (13): 0 ≦ D ≦ arctan (W + CW) / 300 mm (Equation 13). One structure for tilting the illumination direction of the LED element to satisfy the above condition is to mount the LED element on the circuit board at a predetermined inclination angle so that it faces toward the center of the smart device's camera lens. Another structure is to tilt the arrangement of the light-transmitting diffusion plate 113 on the top surface of the orbiting housing 110. FIG. 10 is a simplified diagram illustrating a configuration in which the light emitted from the LED element 121 of the circulating light source 120 is tilted at an inclination angle D. As shown in FIG. 10( a), the inclination angle D is set so that the illumination direction of the LED element is tilted toward the center of the camera lens of the smart device. FIG. 10( b) is a simplified diagram illustrating the light emitted when the inclination angle D is the upper limit value of (Equation 13). In this case, as shown in FIG. 10( b), the condition is such that the light is emitted to converge at a center point 300 mm away. Under these conditions, a subject located 300 mm away will be illuminated most brightly. Even at distances before or after this distance, the light will be illuminated with converged light. The lighting device for smart devices of the present invention has the advantage of being able to capture close-up photography of a subject. Therefore, the condition of (Equation 13) above is considered a preferable range because the subject is brightly illuminated and the photography conditions are improved.

[0048] Next, the right-side mounting fixture 130 and the left-side mounting fixture 140 will be described. The right-side mounting fixture 130 and the left-side mounting fixture 140 are mounting fixtures for mounting the smart device lighting device 100 to the smart device 200. The right-side mounting fixture 130 and the left-side mounting fixture 140 clamp the smart device 200 from the left and right, thereby securing and mounting the smart device lighting device 100 to the smart device 200. The right-side mounting fixture 130 includes a right-side gripping portion 131 that clamps the right edge of the smart device 200 from above and below, and a right-side bridge portion 132 that allows the lateral position of the right-side gripping portion 131 to be adjusted. Similarly, the left-side mounting fixture 140 includes a left-side gripping portion 141 that clamps the left edge of the smart device 200 from above and below, and a left-side bridge portion 142 that allows the position of the left-side gripping portion 141 to be adjusted.

[0049] As can be easily understood by referring to the rear view of the smart device lighting device 100 externally attached to the smart device 200 in Fig. 3(b) and the plan view in Fig. 6(b), the right-side mounting fixture 130 and the left-side mounting fixture 140 clamp the edges of the smart device 200 from the left and right sides with the right-side gripping portion 131 and the left-side gripping portion 141, and the clamping distance is adjusted by the sliding of the right-side bridge portion 132 and the left-side bridge portion 142, respectively. The smart device 200 can be fixed in place while being clamped from the left and right sides (fixing structure not shown).

[0050] In the perspective view of FIG. 1( b), the end of the left bridge portion 142 is visible in the recess on the right edge of the main body 150 of the smart device lighting device 100. The depth of the end face of the left bridge portion 142 may vary depending on the width of the smart device 200; however, in this example, the end face of the left bridge portion 142 is simply visible in the recess on the right edge. As shown in the perspective view of FIG. 1( b), the right bridge portion 132 and the left bridge portion 142 are offset from each other to prevent their sliding directions from overlapping and colliding. While many smartphones are palm-sized, tablet-type information terminals are larger than smartphones. Therefore, to accommodate tablet-type information terminals, an extension bridge member (not shown) may be used to extend the length of the right bridge portion 132 and the left bridge portion 142.

[0051] With the smart device 200 sandwiched and secured between the right-side mounting fixture 130 and the left-side mounting fixture 140, the circulating light source 120 is mounted to surround the camera lens 210 of the smart device. In other words, the smart device lighting device 100 is attached so that the central hole 115 of the circumferential housing 110 is positioned like a window, maintaining an open front of the smart device's camera lens 210. The main body 150 of the smart device lighting device 100 serves as the base for the circumferential housing 110 and also as a base for slidably supporting the right-side mounting fixture 130 and the left-side mounting fixture 140. In this configuration example, the main body 150 is rectangular, but the external shape is not particularly limited. A battery may be built into the main body 150 to provide power for driving the LED element 121.

[0052] Next, smart device 200 is a smartphone or tablet-type information terminal equipped with a camera function. While smart device 200 is not particularly limited, many of the smartphones and tablet-type information terminals that have become popular in recent years generally incorporate a camera lens 210 and are equipped with a camera function. The length, width, and height of the housing of such commonly used smartphones and tablet-type information terminals fall within certain ranges regardless of the manufacturer, so smart device lighting device 100 of the present invention can be externally attached.

[0053] Next, the lighting control and drive control of the LED elements 121 related to the orbiting light source 120 of the smart device lighting device 100 will be described. FIG. 11( a) is a simplified diagram illustrating the circuit configuration of the smart device lighting device 100. Only the components related to the electronic circuit are shown. In this example, as shown in FIG. 11( a), eight LED elements, 121-1 to 121-8, are arranged in a circumferential pattern as the orbiting light source 120. For ease of explanation, the four LED elements, 121-1, 121-2, 121-5, and 121-6, arranged along the vertical axis are referred to as the first group of LED elements 121, and the four LED elements, 121-3, 121-4, 121-7, and 121-8, arranged along the horizontal axis are referred to as the second group of LED elements 121. As shown in FIG. 11, the first group of LED elements 121 can be said to be arranged along the vertical axis, and the second group of LED elements 121 can be said to be arranged along the horizontal axis.

[0054] The number of LED elements 121 is not limited, and the method of dividing the LED elements into groups is also not limited. For convenience of explanation, the following description will be given assuming that there are eight LED elements 121 divided into two groups, the first group and the second group. As shown in FIG. 11( a), in this example, the smart device lighting device 100 includes a switching control unit 160 and a battery 170. The switching control unit 160 and the battery 170 may be built into the main body 150. The switching control unit 160 is an electronic circuit that controls the switching of the LED elements. By incorporating this switching control unit 160 to control the lighting and drive of the LED elements 121, various lighting and drive controls can be performed, beyond simple on / off control using an ON / OFF switch.

[0055] The lighting control of the LED elements 121 by the switching control unit 160 includes an all-on pattern and a lighting pattern for each group. FIG. 11(b) is a diagram illustrating the all-on pattern. In the figure, the lit LED elements 121 are shown in black. The all-on pattern, as shown in FIG. 11(b), is a control that switches between lighting and extinguishing all the LED elements 121. This can be said to be the same control as the lighting / extinguishing control using a simple ON / OFF switch.

[0056] 12A and 12B are diagrams illustrating the first group lighting pattern and the second group lighting pattern. The first group lighting pattern, as shown in FIG. 12A, is a pattern in which the first group of LED elements 121 (four LED elements: LED element 121-1, LED element 121-2, LED element 121-5, and LED element 121-6) are lit, and the second group of LED elements 121 (four LED elements: LED element 121-3, LED element 121-4, LED element 121-7, and LED element 121-8) are extinguished. The second group lighting pattern, as shown in FIG. 12B, is a pattern in which the first group of LED elements 121 are extinguished, and the second group of LED elements 121 are lit. In the figure, the lit LED elements 121 are displayed in black.

[0057] The technical significance of providing lighting patterns for each group is as follows: Because the LED elements 121 are arranged in a circular pattern, the direction and angle of the light emitted from each LED element 121 toward the subject differs, but there are various situations, such as the outer shape of the subject, the three-dimensional uneven shape of the subject, the surface condition of the subject, the color of the subject, the way the user holds the camera lens 210 of the smart device 200, and the relative angle and distance between the subject and the camera lens 210 of the smart device 200. Depending on the case, there may be cases where the full lighting pattern is preferable, cases where the first group lighting pattern in which the LED elements 121 are arranged along the vertical axis is preferable, or cases where the second group lighting pattern in which the LED elements 121 are arranged along the horizontal axis is preferable, and the advantage of being able to select among these is provided.

[0058] FIG. 13 is a diagram illustrating lighting patterns when the LED elements 121 are divided into three groups. As shown in the circuit configuration of FIG. 13(a), the LED elements are divided into a first group arranged along the vertical axis, a second group arranged along the horizontal axis, and a third group with LED elements arranged in the gaps between the first and second groups. The LED elements 121 belonging to the third group in the figure are four LED elements 121-9, 121-10, 121-11, and 121-12, and are arranged in a cross pattern. FIG. 13(b) is a diagram illustrating the third group lighting pattern. The LED elements 121 belonging to the third group in the figure are lit. The lit LED elements 121 are displayed in black in the figure. The first group lighting pattern and the second group lighting pattern may be similar to the lighting patterns in FIGS. 12(a) and 12(b), and illustration of the lighting patterns when the LED elements 121 are divided into three groups is omitted.

[0059] The technical significance of dividing the lighting patterns into three groups as shown in Figure 13 is as follows: In cases where full lighting is preferred, in which all LED elements 121 are lit to increase the light output, in cases where the first group lighting pattern in which the LED elements are arranged along the vertical axis is preferred, in cases where the second group lighting pattern in which the LED elements 121 are arranged along the horizontal axis is preferred, and in cases where good vertical and horizontal balance is preferred but full lighting would produce too much light or when the battery is low and power saving is desired, the third group lighting pattern can be used to achieve a relatively good vertical and horizontal balance and also to save power. In this way, there is the advantage of being able to select the lighting pattern more precisely according to various situations.

[0060] Next, the drive control of the LED element 121 will be described. The drive control of the LED element 121 by the switching control unit 160 includes static drive control (DC drive) and pulse drive control. Static drive control (DC drive) is a lighting method in which current is continuously applied to the LED element 121. The advantage of static drive control (DC drive) is that a constant current is always applied to the LED element 121, so fluctuations in illumination such as flicker do not occur. The disadvantage of static drive control (DC drive) is that power consumption increases and the lifespan of the LED element 121 may be shortened.

[0061] Pulse drive control, also known as dynamic drive control, is a type of drive control that causes the LED elements 121 to blink at a constant frequency at high speed. The advantages of pulse drive control include reduced power consumption and a longer lifespan for the LED elements 121. The advantage of pulse drive control is that it reduces power consumption and extends the lifespan of the LED elements 121. It also allows the length of light emission time to be varied by changing the blinking frequency, thereby enabling the brightness of the LED elements 121 to be controlled and adjusted. The disadvantage of pulse drive control is that when driven at a low frequency, for example, 50 Hz (Hertz) or less, flickering is more noticeable to the human eye, and in camera photography, flicker can cause the amount of light hitting the subject to change at the moment of capture, potentially resulting in an unstable captured image. This flickering, which can lead to unstable captured images, is a major disadvantage, particularly when shooting video at 30 frames per second.

[0062] The smart device lighting device 100 of the present invention is designed to be portable, and when the power source is the battery 170 installed in the main body 150, the advantage of low power consumption of pulse drive control is important. Therefore, a mechanism is provided to reduce the disadvantage of unstable captured images due to flicker when taking photos with the camera of the smart device 200. The first mechanism for stabilizing captured images is to use pulse control to synchronize the timing of the pulse-driven lighting of the LED element 121 with the timing of capturing video frames using the camera shooting function of the smart device 200.

[0063] A second technique for stabilizing captured images is to perform pulse drive control so that at least one of the LED elements 121 is lit at any timing by shifting the phase of the supply current if the LED elements 121 are divided into multiple groups. In particular, in the pattern of Figure 13 where the LED elements 121 are divided into three groups, by shifting the phase of the supply current for pulse drive of the LED elements 121 in the first group, the phase of the supply current for pulse drive of the LED elements 121 in the second group, and the phase of the supply current for pulse drive of the LED elements 121 in the third group evenly (for example, by 120°), pulse drive control can be performed so that at least one of the LED elements 121 is lit at any timing.

[0064] FIG. 14 shows the change in the supply current to each group in a pattern in which the LED elements 121 are divided into three groups. Generally, commercial power sources are three-phase AC, with each phase being a sine wave offset by 120 degrees. Therefore, when the LED elements 121 are divided into three groups, it is convenient to supply current to each group using the current of each phase of the three-phase AC power supply. As shown in FIG. 14 , the supply current for each phase to each group is a sine wave, but the phases are offset by 120 degrees. This ensures that an adequate supply of current to each LED element 121 is ensured at any timing. While there is some pulsation in the light intensity when viewed closely, the circulating light source 120 can be controlled to be nearly constantly illuminated. At the same time, power consumption can be reduced. Incidentally, by including a capacitance element in the supply current circuit for each group, the drop in the sine wave can be smoothed.

[0065] By controlling the lighting and driving of the LED elements 121 related to the circulating light source 120 of the lighting device 100 for smart devices described above, it is possible to control the direction and angle of illumination onto the subject, and also to stabilize the camera shooting function of the smart device 200, particularly the amount of light irradiated onto the subject in each frame of video shooting.

[0066] The lighting device for smart devices of the present invention can be widely used as a lighting device for taking photos with a camera using a smart device such as a smartphone or tablet information terminal.

[0067] 100 Smart device lighting device 110 Surrounding housing 111 Inner peripheral wall surface 112 Outer peripheral wall surface 113 Light-transmitting diffusion plate 114 Bottom surface 115 Hole 120 Surrounding light source 121 LED element 130 Right-side mounting fixture 140 Left-side mounting fixture 150 Main body 160 Switching control unit 170 Battery 200 Smart device 210 Camera lens

Claims

1. A lighting device for smart devices that is attached externally to a smart device equipped with a camera function, comprising: a circular casing with an inner wall surface, an outer wall surface, a bottom surface, and a top surface; a circumferential light source having a plurality of LED elements arranged on the bottom surface of the casing; a circumferential light source that has a light-transmitting and light-diffusing plate attached to the top surface of the casing, has a hole in the center, and emits light from around the hole; and a mounting fixture that is attached to the smart device so that the camera lens of the smart device is positioned at the hole in the circumferential light source.

2. The lighting device for a smart device according to claim 1, wherein the smart device is a smartphone or a tablet-type information terminal.

3. The lighting device for a smart device according to claim 1, wherein the outer shape of the orbiting housing of the orbiting light source is a circular or elliptical ring shape.

4. The lighting device for a smart device according to claim 1, wherein the outer shape of the orbiting housing of the orbiting light source is a polygonal orbiting shape.

5. A lighting device for smart devices as described in claim 1, wherein the diameter of the hole of the orbiting light source formed by the inner wall surface of the orbiting housing is 2 cm to 7 cm.

6. The lighting device for smart devices according to claim 1, characterized in that the distance H from the height of the LED elements to the height of the light-transmitting diffusion plate on the upper surface and the distance W from the position of the LED elements to the inner wall surface of the surrounding housing satisfy the following condition (Equation 1). (Equation 1) 0.5W≦H≦5.7W 7. The lighting device for a smart device according to claim 1, characterized in that the height CH of the inner peripheral wall surface of the circumferential housing and the distance CW from the center of the camera lens of the smart device to the inner peripheral wall surface of the circumferential housing satisfy the following condition (Equation 2). (Equation 2) 1 mm ≦ CH ≦ 1.7 CW 8. The lighting device for a smart device according to claim 1, characterized in that the irradiation direction of the LED element is tilted toward the center of the camera lens of the smart device at an inclination angle D that satisfies the condition of the following (Equation 3): 0≦D≦arctan (W+CW) / 300 mm (Equation 3) 9. The lighting device for smart devices according to claim 1, further comprising a switching control unit that performs switching control of the LED elements, and wherein the lighting of the plurality of LED elements is controlled by the switching control unit.

10. A lighting device for a smart device as described in claim 9, wherein the number of the LED elements arranged on the bottom surface of the surrounding housing is four or more, there are at least a first group and a second group, and the control of the lighting of the LED elements by the switching control unit includes an all-lighting pattern that lights up the LED elements of the first group and the second group, a first group lighting pattern that lights up the LED elements of the first group and turns off the LED elements of the second group, and a second group lighting pattern that turns off the LED elements of the first group and lights up the LED elements of the second group.

11. The lighting device for a smart device as described in claim 10, further comprising a third group in addition to the first and second groups as groups of the LED elements, wherein in control of the lighting of the LED elements by the switching control unit, the full lighting pattern is a pattern in which all of the LED elements from the first group to the third group are lit, and further comprising, in addition to the first group lighting pattern and the second group lighting pattern, a third group lighting pattern in which the LED elements of the first and second groups are turned off and only the third group is lit.

12. The lighting device for a smart device according to claim 9, characterized in that the control of lighting of the LED elements by the switching control unit is static driving.

13. A lighting device for a smart device as described in claim 9, characterized in that the control of the lighting of the LED element by the switching control unit is pulse driving, and the timing of the pulse driving of the lighting of the LED element is synchronized with the timing of capturing video frames by the camera shooting function of the smart device.

14. The lighting device for a smart device described in claim 11, characterized in that the control of lighting of the LED elements by the switching control unit is pulse driving, and the phase of the supply current for pulse driving of the LED elements of the first group, the phase of the supply current for pulse driving of the LED elements of the second group, and the phase of the supply current for pulse driving of the LED elements of the third group are shifted, so that at least any of the LED elements is controlled to light up regardless of the timing.

15. The lighting device for smart devices according to claim 1, characterized in that the color temperature CT of the LED element is in the range of the following (Equation 4), and the color rendering index Ra of the LED element is in the range of the following (Equation 5). (Equation 4) 4000K≦CT≦6500K (Equation 5) 90≦Ra<100

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