Lighting device

Abstract

The present invention provides a lighting device that illuminates objects such as signage devices in a way that makes them appear to flash, thereby enhancing the visibility and attention-grabbing nature of the illuminated objects. [Solution] The present invention provides a lighting device comprising a lighting unit 3 which alternately irradiates an object with light from both light sources, comprising a first light source 31 consisting of RGB type LEDs that emit white light and a second light source 32 consisting of yellow phosphor type LEDs that emit white light, and a light emission control unit 4 which controls the light emission mode of both light sources 31 and 32. The light emission control unit 4 comprises a signal generation unit 42 which includes at least one control unit of a waveform control unit 421, a frequency control unit 422, a level control unit 423, and a duty cycle control unit 424. The setting unit 41 sets the control in the signal generation unit 42 based on the surrounding conditions of the object.

Description

【Technical Field】 【0001】 The present invention relates to a lighting device for illuminating an object, and more particularly to a lighting device capable of enhancing the visibility (ease of visual confirmation) and the attractiveness (ease of visual attention) of the illuminated object. 【Background Art】 【0002】 The applicant has previously proposed in Patent Document 1 a lighting device for enhancing the visibility and attractiveness of illuminated objects such as road signs. The technology of Patent Document 1 includes a first light source and a second light source that emit light with substantially the same color temperature but different spectral characteristics, and controls the lighting of the first light source and the second light source to alternately irradiate the illuminated object with the light emitted from each light source. 【0003】 According to this technology, even when the illuminated object is alternately illuminated by the first light source and the second light source, the same visibility as when the illuminated object is illuminated with a constant brightness can be obtained. On the other hand, since the spectral characteristics of the two light sources are different, for a predetermined color portion of the illuminated object, the brightness changes following the alternating lighting of the two light sources, resulting in a blinking appearance. This enhances the visibility of the illuminated object and improves the attractiveness to the illuminated object. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Patent No. 6669428 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 When the applicant further examined the technology of Patent Document 1, it was found that there are the following problems to be improved. (Problem 1) When the first and second light sources, which emit light at a predetermined brightness, are simply turned on alternately, the change in brightness is monotonous, and higher visibility and attention-grabbing properties are desired. (Problem 2) Although the white light from the first light source and the white light from the second light source have almost the same color temperature, the first light source appears brighter to the human eye when the brightness is the same. Also, when switching between the first and second light sources, even though they are both white, a color shift may be perceived, similar to the difference between daylight and incandescent light, causing discomfort. (Problem 3) The first and second light sources are switched on alternately at a frequency of 2-4 Hz, but some people find the rapid change in brightness bothersome. 【0006】 Regarding (Problem 2), the present inventors have provided the following non-patent literature. "J-STAGE Advance published date:2022.March.16" (https: / / doi.org / 10.2150 / jieij.20000596) According to this document, "RGB-LED lighting (LEDs that emit red, green, and blue light, mixing the light from each LED to produce white light) has been found to have a higher perceived brightness and give a yellowish-green color perception than white light sources (LEDs that emit blue light and phosphors that emit yellow light to produce white light)." 【0007】 The object of the present invention is to resolve the above-mentioned problems (1) to (3), and to provide a lighting device that further enhances visibility and attention-grabbing properties, especially when applied to road signs as the object to be illuminated. [Means for solving the problem] 【0008】 The present invention provides a lighting unit comprising a first light source and a second light source that emit light having substantially the same color temperature but different spectral characteristics, and which alternately irradiates an object with light from both light sources, and a light emission control unit that controls the light emission mode of the first and second light sources of the lighting unit. The light emission control unit comprises at least one control unit, which includes a waveform control unit that controls a waveform showing the change in the light emission level of both light sources on the time axis, a frequency control unit that controls the frequency which is the number of alternations per unit time of both light sources, a level control unit that controls the light emission level of both light sources, and a duty cycle control unit that controls the duty cycle of the high-level time in one cycle of the light emission level of both light sources. Furthermore, the light emission control unit is configured to set the control of the light emission control unit based on the surrounding conditions of the object. 【0009】 In the present invention, the waveform shaping unit, frequency control unit, level control unit, and duty cycle control unit are preferably configured as follows. Specifically, the waveform control unit controls the waveform to one of the following: a square wave including a trapezoidal wave, a triangular wave, a sine wave, or a cosine wave. The frequency control unit can control the alternating frequency in the range of 0.5 Hz to 5 Hz, and by setting in the setting unit, it is possible to select and control any frequency in the range of 0.5 Hz to less than 2 Hz and in the range of 2 Hz to 5 Hz. The level control unit sets the maximum value of the light emission level to 100% and controls the minimum value in the range of 5% to 50% of the maximum value. The duty cycle control unit controls the duty cycle of the first light source to a ratio less than 1 / 2. 【0010】 In the present invention, the lighting unit comprises a light source section having a first light source and a second light source, and an optical section that optically controls the light from the first light source and the second light source and irradiates it toward an object, wherein the optical section preferably comprises an aperture diaphragm that selectively transmits light emitted from the light source section, a pre-lens that transmits the light transmitted through the aperture diaphragm in a divergent state, an irradiation lens that optically controls and emits the light transmitted through the pre-lens, and an outer lens that emits the light emitted from the irradiation lens in a diffuse state. Herein, the illumination device according to claim 7, wherein the aperture diaphragm selectively transmits white light emitted from the first light source. [Effects of the Invention] 【0011】 According to the present invention, by alternately illuminating an object with a first light source and a second light source, visibility similar to that obtained by illuminating the object with a constant brightness can be obtained. On the other hand, due to the difference in the spectral characteristics of the two light sources, the brightness changes following the alternating emission of the two light sources, resulting in a flashing appearance. Further, by controlling the waveform, frequency, emission level, and duty ratio during alternating emission by a light emission control unit based on the surrounding situation, the visibility of the object is enhanced and the attractiveness to the object is improved. 【Brief Description of the Drawings】 【0012】 [Figure 1] Conceptual configuration diagram of an embodiment of the lighting device of the present invention. [Figure 2] Surface view of the signboard of a road sign. [Figure 3] Vertical cross-sectional view showing the schematic configuration of the lighting device. [Figure 4] Diagram showing the conceptual configuration of the light source unit. [Figure 5] Spectral diagram of the first light source (three-color light source) and the second light source (white light source). [Figure 6] Schematic diagram for explaining the action of the aperture stop. [Figure 7] Block configuration diagram of the light emission control unit. [Figure 8] Timing diagram of the light emission form of the light source in the initial setting. [Figure 9] Timing diagram of the light emission form of the light source in the waveform control. [Figure 10] Timing diagram of the light emission form of the light source in the level control [Figure 11] Timing diagram of the light emission form of the light source in the duty control. [Figure 12] Conceptual configuration diagram of a modification of the lighting device of the present invention. 【Embodiments for Carrying Out the Invention】 【0013】 Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual configuration diagram of Embodiment 1 configured as a lighting device that illuminates a road sign as an object to be illuminated by the present invention. A stop road sign 2 is erected on a part of the road. On the surface of the sign board 21 of this road sign 2, as shown in FIG. 2, a sign pattern 2b consisting of white characters "Stop" is described on a red background 2a surrounded by a white frame. The sign board 21 is fixedly supported at the upper end of a support column 22 erected on the ground. Further, a lighting device 1 is supported by a support arm 23 at an upper position of this sign board 21. And when the lighting device 1 emits light, the light emitted from the lighting device 1 illuminates the surface of the sign board 21. In the lighting device 1 of the embodiment, the light emission form is controlled so as to enhance the visibility and conspicuity with respect to the road sign 2 during this lighting. 【0014】 FIG. 3 is a longitudinal sectional view showing a schematic configuration of the lighting device 1, and includes a lighting unit 3 assembled in an outer casing composed of a container-type case 38 with an open front surface and an outer lens 37 attached to the opening of this case 38, and a light emission control unit 4 installed inside the case 38 to control the light emission form of the lighting unit 3. 【0015】 The lighting unit 3 further includes a light source unit 30 and an optical unit 33 that irradiates the light emitted from this light source unit 31 from the outer lens 37. The light source unit 30 includes a first light source 31 and a second light source 32. FIG. 4 is a diagram showing a conceptual configuration of the light source unit 30. The first light source 31 includes three LEDs (light emitting diodes) 31R, 31G, 31B that emit and emit red (R), green (G), and blue (B) lights respectively. The blue light, green light, and red light emitted from these three LEDs 31R, 31G, 31B are synthesized to emit white light. Hereinafter, the first light source composed of the three LEDs 31R, 31G, 31B will be referred to as a three-color light source 31. 【0016】 The second light source 32 is composed of an LED 32W which is excited by the light emitted from a blue LED that emits blue light and emits yellow light, and emits white light when the blue (B) light and yellow (Y) light are combined. Hereafter, the second light source composed of this white light emitting LED 32W will be referred to as the white light source 32. The three RGB LEDs 31R, 31G, and 31B that constitute the first light source tricolor light source 31 and the white light source 32 as the second light source are housed in a single package P with their respective light-emitting surfaces facing the same direction, thereby forming the light source unit 3. 【0017】 The light emitted from the tricolor light source 31 and the white light source 32 is white light with almost the same color temperature, but the spectral distribution of the light emitted from each light source 31 and 32 is different. Figure 5(a) shows the spectral distribution characteristics of the tricolor light source 31, where the color temperature of the white light is approximately 5000 K (Kelvin), but the spectral distribution has high luminosity levels in each wavelength region of blue, green, and red. Figure 5(b) shows the spectral distribution characteristics of the white light source 32, where the color temperature of the white light is approximately the same as that of the tricolor light source 31, 5000 K, but the spectral distribution has a high luminosity level of blue light, while the luminosity levels in the yellow, i.e., green to red wavelength region are relatively low. 【0018】 As shown in Figure 2, the optical unit 33 includes an aperture diaphragm 34 that selectively transmits light emitted from the light source unit 31, a pre-lens 35 that spreads the light beam (light beam) of light transmitted through the aperture diaphragm 34, and an illumination lens 36 that optically controls the light incident from the pre-lens 35 and illuminates substantially the entire area of ​​the outer lens 37. 【0019】 As shown in the schematic diagram in Figure 6, viewed from the side of the light source unit 30, the aperture diaphragm 34 transmits the white light LW formed by mixing the red light LR, green light LG, and blue light LB emitted from the three RGB LEDs 31R, 31G, and 31B that constitute the three-color light source 31. Therefore, the red, green, and blue light that are not mixed into white light are not transmitted through the aperture diaphragm 34, preventing these colored lights from being emitted from the lighting device 1. The white light emitted from the white light source 32W is also transmitted through this aperture diaphragm 34. 【0020】 The pre-lens 35 is composed of, for example, a fly-eye lens and is embedded inside the aperture diaphragm 34. By diffusing, or rather diverging or scattering, the white light transmitted through the pre-lens 35 expands the light beam and equalizes the brightness distribution of the transmitted white light. The light transmitted through the pre-lens 35 is incident on the illumination lens 36. The illumination lens 36 is composed of a convex lens, and by appropriately setting the distance between the lens and the pre-lens 35, the white light is optically controlled and incident on almost the entire surface of the outer lens 37. The outer lens 37 is composed of, for example, a translucent plate with a textured surface, and transmits the incident white light by diverging or scattering, and then emits it as white light with a uniform brightness distribution. The white light emitted from this outer lens 37 is irradiated onto the sign board 21 of the road sign 2 shown in Figure 1. 【0021】 Figure 7 is a block diagram of the light emission control unit 4 that controls the light emission of the light source unit 30. The light emission control unit 4 includes a setting unit 41 that can automatically or manually set the light emission patterns of the tricolor light source 31 and the white light source 32, a signal generation unit 42 that generates signals to cause the tricolor light source 31 and the white light source 32 to emit light based on the light emission patterns set by the setting unit 41, and a drive unit 43 that drives the tricolor light source 31 and the white light source 32 individually to emit light based on the generated signals. Note that the power supply system is omitted in Figure 7. 【0022】 The setting unit 41 sets the emission state of the three-color light source 31 and the white light source 32 in response to changes or differences in the surrounding conditions of the location where the road sign 1 is installed. Surrounding conditions include, for example, ambient brightness, weather, and road traffic conditions. The setting unit 41 is equipped with various sensors to detect these surrounding conditions. For example, it is equipped with an illuminance sensor 411 to detect ambient brightness, and a raindrop sensor 412 and a temperature sensor 413 to detect weather conditions. In addition, to detect road traffic conditions, it is equipped with an imaging device 414 that captures images of vehicles and pedestrians traveling on the road, or a radar device 415 such as LiDAR that detects vehicles and pedestrians and also detects the speed and direction of movement of the detected vehicles and pedestrians. The setting unit then automatically controls the emission mode of each LED based on the surrounding conditions detected by each sensor. In this embodiment, it is also possible to set the lights by manually operating the manual setting device 416 based on the surrounding conditions detected by each sensor 411 to 415 or the surrounding conditions directly perceived by a person. 【0023】 The signal generation unit 42 is equipped with a function generator (hereinafter referred to as FG) 420 capable of generating arbitrary signals. This FG 420 can generate voltage signals of multiple different waveforms at arbitrary frequencies. Here, the frequency is the frequency at which the LED alternates between illumination and extinction, or between high-level illumination and low-level illumination. As will be described later, this frequency is the frequency at which the three-color light source 31 and the white light source 32 alternately illuminate. The configuration of the FG 420 is already known, so a detailed explanation will be omitted. The FG 420 is connected to a waveform control unit 421, a frequency control unit 422, a level control unit 423, and a duty cycle control unit 424. These control units 431 to 424 control the FG 420 based on the settings in the setting unit 41, and control the waveform, frequency, level, and duty cycle of the signals generated by the FG 420. 【0024】 The functional configuration of the FG420 allows for the generation of signals with waveforms such as square waves, trapezoidal waves, triangular waves (sawtooth waves), and sine waves (or cosine waves) via control of the waveform control unit 421. The frequency control unit 422 allows for the generation of signals with any frequency in the range of 0.5Hz to 5Hz. The level control unit 423 controls the signal level, i.e., the maximum and minimum values ​​of the signal amplitude. For example, the minimum value can be controlled within a range of approximately 0% to 50% of the maximum value. The duty cycle control unit 424 controls the duty cycle of the signal. The duty cycle is the ratio of the high-level time in one period of the signal. This embodiment applies when the generated signal is a square wave, but other waveforms may also be used. 【0025】 The drive unit 43 includes V / I (voltage / DC) converters 431 and 432 that convert the voltage signal generated by the signal generation unit 42 into a drive current and supply it to the tricolor light source 31 and the white light source 32, respectively. In addition, an alternating controller 430 is connected to the signal path of one of the light sources, in this case the tricolor light source 31, and controls the signal transmitted through that signal path so that the tricolor light source 31 and the white light source 32 emit light alternately. This alternating controller 430 may control the signal level by inverting it between high and low, or it may control the phase of one signal so that it is phase-shifted relative to the phase of the other. 【0026】 In the lighting device 1 with the above configuration, the three-color light source 31 and the white light source 32 of the light source unit 3 are alternately illuminated by the light emission control unit 4 to illuminate the road sign 2. Furthermore, the light emission control unit 4 controls the emission pattern of the three-color light source 31 and the white light source 32 based on the surrounding conditions of the location where the road sign 2 is installed. This enhances the visibility and attention-grabbing power of the road sign 2. This light emission control will now be explained. 【0027】 Figure 8 shows the timing of white light emission L1 and L2 emitted by the tricolor light source 31 and the white light source 32 in the initial (default) state of the light emission control unit 4. The horizontal axis is time t, and the vertical axis is brightness (luminance or luminous intensity) at the time of emission. The solid line L1 is the white light from the tricolor light source 31, and the dashed line L2 is the white light from the white light source 32. The light emission control unit 4 generates a square wave of a predetermined frequency in the FG420, and the drive unit 43 controls the emission of both light sources 31 and 32 using this signal, so that both light sources 31 and 32 emit light alternately at a predetermined period. That is, when the tricolor light source 31 emits light, the white light source 32 is extinguished, and when the white light source 32 emits light, the tricolor light source 31 is extinguished. In this initial setting, the frequencies of the white light L1 and L2 emitted alternately by both light sources 31 and 32 are set to frequencies suitable for humans to comfortably perceive the on and off of each light source, for example, in the range of 2 to 4 Hz. 【0028】 When the emission modes of the tricolor light source 31 and the white light source 32 are controlled to their initial settings, the road sign 2 shown in Figure 1 is alternately illuminated by the white light L1 of the tricolor light source 31 and the white light L2 of the white light source 32. As shown in Figure 2, the road sign 2 has a white sign pattern 2b formed on a red background 2a, and the spectral distributions of the white lights L1 and L2 of the tricolor light source 31 and the white light source 32 are as shown in Figure 5. Therefore, even when the white sign pattern 2b is alternately illuminated by the white lights L1 and L2 of both light sources 31 and 32, the color temperatures of both white lights L1 and L2 are almost equal, so it appears to have almost the same white appearance visually. In other words, it has a white appearance with almost constant luminous intensity, regardless of the alternate illumination by the tricolor light source 31 and the white light source 32. 【0029】 On the other hand, the red background 2a of road sign 2 has a high reflectivity in the red wavelength region, so when illuminated by the white light L1 of the tricolor light source 31, the red background 2a appears bright. Conversely, when illuminated by the white light L2 of the white light source 32, the red background 2a becomes dark. Therefore, when road sign 2 is alternately illuminated by the white light L1 and L2 of the tricolor light source 31 and the white light source 32, the white sign pattern 2b is observed as a continuously bright white, but the red background 2a alternates between appearing bright and dark, resulting in a visually flashing appearance. This makes it possible to improve the visibility and attention-grabbing power of road sign 2 for people observing it. 【0030】 Thus, even in the initial light emission mode, the brightness of the red background 2a of the road sign 2 is changed alternately, providing visibility and attention-grabbing properties. However, this light emission mode suffers from the aforementioned (Problem 1) to (Problem 3). Therefore, in this embodiment, as will be explained below, the signal generated by the signal generation unit 42 is controlled by the setting unit 41 of the light emission control unit 4, thereby controlling the light emission modes of the three-color light source 31 and the white light source 32, further enhancing visibility and attention-grabbing properties. 【0031】 Figure 9 is a timing diagram showing the light emission patterns when the waveform of the initial signal in the light emission control unit 4 is changed. The initial waveform is rectangular, but the waveform control unit 421 of this embodiment can generate triangular waves and sine waves using the FG420. The light emission patterns of the tricolor light source 31 and the white light source 32 are then controlled based on the generated signals. Figure 9(a) is a timing diagram for a triangular wave, where the light emission levels of the white light sources L1 and L2 of the tricolor light source 31 and the white light source 32 are gradually increased or decreased in a linear fashion. Figure 9(b) is a timing diagram for a sine wave, where the white light sources L1 and L2 are gradually changed in a sine fashion. 【0032】 Thus, in alternating emission control of white light L1 and L2 using triangular or sine waves, there is almost no time when the emission level is kept constant, and the emission pattern is such that the mixing ratio of white light L1 and L2 changes over time and continuously. As a result, the brightness of the red background 2a of the road sign 2 also changes over time and continuously, resulting in a unique appearance with a sense of pulsation. Therefore, visibility and attention-grabbing power are enhanced in a state where the irritation is reduced compared to the brightness change using a square wave in the initial setting, and (Problem 1) can be resolved. This sense of pulsation can be obtained regardless of the difference in the frequency of alternating emission, so there is no constraint on the controlled frequency. In addition, even when the waveform is controlled, the overall emission level of the mixture of both white light L1 and L2 from the tricolor light source 31 and the white light source 32 is kept constant. 【0033】 The timing of the frequency control unit 422 in the light emission control unit 4 is changed from the frequency shown in the initial timing diagram in Figure 8, so the illustration is omitted. As mentioned above, the initial frequency is set to 2 to 4 Hz, but in the embodiment, the frequency control unit 422 is controlled to a range of 0.5 Hz to less than 2 Hz, or a range higher than 2 Hz up to 5 Hz (for example, a range higher than 4 Hz up to 5 Hz) when the waveform generated by the FG420 is a square wave or a trapezoidal wave. 【0034】 The technology described in Patent Document 1 uses a three-color light source 31 and a white light source 32 that emit alternating light with a rectangular wave or trapezoidal wave and an alternating frequency of 2 to 4 Hz. At this frequency, the rate of change in brightness of the red background 2a of the road sign 2 is fast, which causes some people to find it bothersome (Problem 3). In this embodiment, the alternating frequency can be controlled to a frequency lower than 2 Hz, between 0.5 Hz and less than 2 Hz. This frequency control reduces the rate of change in brightness of the red background 2a of the road sign 2, making it slower and less bothersome for viewers. Note that this frequency control applies when the waveform is rectangular; when the waveform is triangular or sine wave, it has unique visibility and attention-grabbing properties, so even if the frequency is controlled in the range of 0.5 Hz to 5 Hz, it will not cause any discomfort. 【0035】 Figure 10 is a timing diagram of the light emission levels when the initial signal level in the light emission control unit 4 is changed. In the initial setting, the maximum value of the light emission levels of the three-color light source 31 and the white light source 32 is 100%, and the minimum value is controlled to 0% of the maximum value. That is, when one light source is emitting light at 100% level, the other light source is extinguished. 【0036】 The level control unit 423 of the embodiment controls the tricolor light source 31 and the white light source 32 so that when the maximum value is 100%, the minimum value is 0 to 50% of the maximum value. For example, as shown in Figures 10(a) to (c), when one of the tricolor light source 31 or the white light source 32 emits light at 100% brightness, the other emits light at 5%, 20%, or 50% brightness. 【0037】 In this level control, when both light sources 31 and 32 are emitted alternately, the 100% white light from one source is mixed with the white light from the other source in proportions of 5%, 20%, and 50%, so that the color of the white light is averaged according to the mixing percentage. This mitigates the differences in brightness and color shifts (Problem 2) that occurred between the white light L1 of the tricolor light source 31 and the white light L2 of the white light source 32. In other words, the perception that the white light from the tricolor light source 31 is brighter than the white light from the white light source 32, as shown in non-patent literature, is mitigated, improving visibility and attention-grabbing properties in this respect. 【0038】 Furthermore, when the white light from one light source is mixed with the white light from the other light source at a ratio of 5-50%, the overall brightness of the white light increases accordingly. To avoid this, the overall brightness of the white light can be controlled to a constant level by adjusting the maximum emission levels of both light sources in proportion to the mixing ratio. In addition, since the white light from both light sources is constantly mixed at a ratio of 100% and 5-50%, the difference in brightness between the red background 2a of road sign 2 is reduced. Consequently, even if the frequency of the police box is high, it becomes less bothersome, and the system is less constrained by the frequency of the police box. 【0039】 Figure 11 is a timing diagram showing the light emission pattern when the initial duty cycle of the signal in the light emission control unit 4 is changed. The duty cycle is defined as the ratio of the time at a level higher than the midpoint between the highest and lowest values ​​of the signal to one period of the signal. Initially, the duty cycle is controlled to 50%. 【0040】 In this embodiment, the duty cycle control unit 424 controls the duty cycle of the white light L1 of the tricolor light source 31 to less than 1 / 2. Consequently, the duty cycle of the white light L2 of the white light source 32 is controlled to be greater than 1 / 2. In other words, in one cycle of the alternating frequency, the emission time of the tricolor light source is controlled to be shorter than the emission time of the white light source. 【0041】 With the default duty cycle, the duty cycles of the alternatingly emitted tricolor light source 31 and the white light source 32 (white light L1 and L2) are equal. As shown in (Problem 2), the white light L1 of the tricolor light source 31 appears brighter than the white light L2 of the white light source 32. Consequently, the tricolor light source 31 becomes highly adaptable to the white light L1, while the visibility of the white light L2 of the white light source 32 is reduced. By controlling the duty cycle of the tricolor light source 31 to shorten its emission time, its adaptability is reduced, improving the visibility of the white light source 32. Therefore, (Problem 2) can be improved. 【0042】 Furthermore, with the lighting device 1 configured as described above, the setting unit 41 detects the surrounding conditions and controls the light emission pattern, thereby enabling suitable lighting that responds to changes in the surrounding conditions. In the following description, although not shown in the figures, for example, the imaging device 414 and radar device 415 may be used to detect vehicles traveling near the road sign 2, and the light emission pattern may be changed and controlled when it is detected that the vehicle is in a distant area beyond a predetermined distance from the road sign 2, and when the vehicle moves to a nearby area closer than the predetermined distance. 【0043】 For example, when a vehicle detected by the setting unit 41 is located in a distant area beyond a predetermined distance from the road sign 2, the frequency control unit 422 controls the frequency of the alternating emission of the three-color light source 31 and the white light source 32 to a frequency higher than 2Hz up to 5Hz (for example, a frequency higher than 4Hz up to 5Hz). This increases the rate of change in brightness of the red background 2a of the road sign 2, improving visibility and attention-grabbing ability for vehicles in the distant area. Conversely, when the detected vehicle moves to a nearby area closer than the predetermined distance, the frequency is controlled to a low frequency of 0.5Hz to less than 2Hz. This reduces the rate of change in brightness of the red background 2a of the road sign 2, alleviating inconvenience for nearby vehicles. 【0044】 Alternatively, in the level control unit 423, when the vehicle is in the distant region, the emission levels of the tricolor light source 31 and the white light source 32 are controlled to the initial maximum value of 100% and the minimum value of 0%, respectively. However, as the vehicle approaches the road sign 2, the minimum value is increased to 5%, 20%, and 50%. When the vehicle is in the distant region, the difference in brightness between the white lights L1 and L2 of both light sources 31 and 32 is difficult to perceive, so the difference in brightness between the red background 2a is increased to ensure visibility and attention. When the vehicle approaches, the visibility and attention to the red background a of the road sign 2 can be ensured, so the difference in brightness between the white lights L1 and L2 of both light sources 31 and 32 is not perceived. 【0045】 Furthermore, the waveform control unit 421 controls the waveform to the initial rectangular wave when the vehicle is in the distant region, but controls it to a triangular wave and then a sine wave when the vehicle approaches the road sign 2. When the vehicle is in the distant region, a steeper change in brightness of the red background 2a of the road sign 2 can improve visibility and attention-grabbing ability from vehicles in the distant region. When the vehicle approaches, the triangular wave and sine wave create a pulsating effect on the red background 2a, resulting in a unique appearance with a pulsating feel, which improves visibility and attention-grabbing ability while reducing irritation. 【0046】 Furthermore, the duty cycle control unit 424 controls the duty cycle to the initial setting when the vehicle is in the distant area, but controls the duty cycle of the tricolor light source 31 to be lower when the vehicle approaches the road sign 2. When the vehicle is in the distant area, a constant change in brightness of the red background 2a of the road sign 2 can improve visibility and attention-grabbing ability from vehicles in the distant area. When the vehicle approaches, lowering the duty cycle of the tricolor light source 31 and shortening the emission time of the white light L1 reduces adaptability, which improves the visibility of the white light L2 of the white light source 32. 【0047】 In contrast to the control methods described above, the light emission mode may also be controlled based on differences in brightness as ambient conditions. For example, control may be based on weather conditions such as sunny or cloudy days, time of day such as twilight or nighttime, or regional differences such as urban or suburban areas. In this case, the setting unit 41 of the light emission control unit 4 detects ambient conditions based on the detection of the illuminance sensor 411, raindrop sensor 412, temperature sensor 413, and imaging device 414. While a detailed explanation of specific examples of control based on ambient conditions is omitted, it is preferable to control the light emission mode to prioritize visibility and attention-grabbing properties due to the difference in brightness of the red background 2a over differences in perceived brightness and color shift between the three-color light source 31 and the white light source 32 when the road sign 2 is difficult to see, and to control the light emission mode to prioritize differences in perceived brightness and color shift between the white lights L1 and L2 when the road sign 2 is easy to see. 【0048】 In the above explanation, examples were shown in which the waveform control unit 421, frequency control unit 422, level control unit 423, and duty cycle control unit 424 in the light emission control unit 4 are controlled independently. However, it is also possible to perform control by appropriately combining the controls of each of these control units. For example, when controlling to a square wave, frequency control may be combined, or level control and duty cycle control may be combined. Furthermore, frequency control, level control, and even duty cycle control may be appropriately selected and combined without being limited to a specific waveform. 【0049】 The light emission control in the light emission control unit 4 described above is not necessarily performed automatically by the setting unit 41. Therefore, a person may perceive the surrounding situation based on the detection by each sensor 411 to 415 and manually control the light emission pattern in the setting unit 41 by operating the manual setting device 416 based on that perception. Alternatively, a person may directly perceive the surrounding situation without relying on the detection by each sensor 411 to 415 and perform the control in the setting unit 41. 【0050】 The illumination device of this embodiment is an example applied to a sign whose sign surface is configured as a light-reflecting surface, but the illumination device of the present invention can also be applied to signs whose sign surface is configured as a light-transmitting surface. Various types of such light-transmitting signs have already been proposed, so a description of specific examples will be omitted here, but a sign pattern or sign surface can be formed on the surface of a light-transmitting substrate using a light-transmitting colored film. Then, an illumination device is installed on the back side of the sign surface, and the light emitted from this illumination device is transmitted through the sign surface. By alternately emitting a tricolor light source and a white light source, the colored sign pattern will appear to be blinking, improving its visibility. 【0051】 The lighting device of the present invention may be configured to be mounted on a vehicle to illuminate road signs. Figure 12 is a conceptual diagram of a modified example in which the lighting device 1 is configured as an auxiliary lighting lamp such as a clearance lamp, daytime running lamp, or overhead lamp for an automobile (CAR). Combination-type front lamps FL are arranged on the left and right sides of the front of the automobile (CAR), and a clearance lamp CL is arranged within these front lamps FL together with a high beam lamp HiL and a low beam lamp Lo. This clearance lamp CL is configured as the lighting device 1 of the present invention. 【0052】 The configuration of this clearance lamp CL is largely the same as that of the lighting device 1 described in the embodiment, and includes a lighting unit 3 and a light emission control unit 4. On the other hand, the configuration of the pre-lens 35 and outer lens 37 is different, and is configured to enable light irradiation with the required light distribution for the clearance lamp CL. As a result, when the clearance lamp CL is turned on, the three-color light source 31 and the white light source 32 of the light source unit 30 emit light, and the white light emitted from each light source 31 and 32 is irradiated toward the front of the automobile CAR with the required light distribution. 【0053】 In this modified example, when the clearance lamp CL is illuminated, the tricolor light source 31 and the white light source 32 alternately emit light to illuminate the area in front of the automobile CAR. Therefore, areas other than road signs, such as the road surface, are illuminated with white light of almost constant intensity regardless of the alternating illumination of each LED, ensuring visibility of the area in front of the automobile. As for road signs, when the light emitted from the clearance lamp CL illuminates them, the road signs appear to change in brightness. By controlling the emission patterns of the tricolor light source 31 and the white light source 32 in the light emission control unit 4, the visibility and attention-grabbing properties of road signs are improved, as in the embodiment, and the difference in perceived color shift in the brightness of the white light is also improved. 【0054】 In the present invention, the first and second light sources are not limited to the tricolor light source and white light source described in the embodiments. Any light source whose color temperature is the same or nearly the same, but whose spectral characteristics differ in a predetermined wavelength range, can be used as the first and second light sources of the present invention. 【0055】 Although the embodiments described above apply the present invention to lighting devices for road signs and auxiliary lighting lamps for automobiles, it can be applied to a wide range of lighting devices, such as lighting devices for illuminating billboards and advertisements, and lighting devices for illuminating posters and other printed materials. [Explanation of Symbols] 【0056】 1. Lighting device 2. Road signs (objects) 2a Red background 2b Labeling Pattern 3 Lighting Unit 4. Light emission control unit 30 Light source section 31 1st light source (three-color light source) 32 Second light source (white light source) 31R, 31G, 31B, 32W LED (light-emitting element) 33 Optics Department 34 Aperture diaphragm 35 Prelens 36 Irradiation Lenses 37 Outer Lens 38 cases 41 Setting section 42 Signal Generation Unit 43 Drive unit 420 Function Generator 421 Waveform Control Unit 422 Frequency Control Unit 423 Level Control Unit 424 Duty Control Unit L1 Three-color light source (white light) L2 White light source

Claims

[Claim 1] A lighting device comprising a lighting unit that alternately irradiates an object with light from a first light source and a second light source that emit light having almost the same color temperature but different spectral characteristics, and a light emission control unit that controls the light emission form of the first light source and the second light source of the lighting unit, wherein the light emission control unit comprises at least one control unit, which includes a waveform control unit that controls a waveform indicating the change in the light emission level of the two light sources on the time axis, a frequency control unit that controls the frequency which is the number of alternations per unit time of the two light sources, a level control unit that controls the light emission level of the two light sources, and a duty cycle control unit that controls the duty cycle of the high-level time in one cycle of the light emission level of the two light sources, and is configured to set the control of the light emission control unit based on the surrounding conditions of the object. [Claim 2] The lighting device according to claim 1, wherein the first light source is composed of three light-emitting elements that emit red light, green light, and blue light, respectively, and the light from each light-emitting element is mixed to emit white light, and the second light source is composed of a light-emitting element that emits blue light and a phosphor that emits yellow light based on the light from this light-emitting element, and emits white light. [Claim 3] The lighting device according to claim 1, wherein the waveform control unit controls the waveform to any of the following: a rectangular wave including a trapezoidal wave, a triangular wave, a sine wave, or a cosine wave. [Claim 4] The lighting device according to claim 1, wherein the frequency control unit can control the frequency of the alternating light within a range of 0.5 Hz to 5 Hz, and can select and control frequencies within a range of 0.5 Hz to less than 2 Hz and a range of over 2 Hz up to 5 Hz by setting in the setting unit. [Claim 5] The lighting device according to claim 1, wherein the level control unit controls the maximum value of the light emission level to 100% and the minimum value to a range of 5% to 50% of the maximum value. [Claim 6] The lighting device according to claim 1, wherein the duty control unit controls the duty cycle of the first light source to a ratio less than 1 / 2. [Claim 7] The lighting device according to claim 2, wherein the lighting unit comprises a light source section having the first light source and the second light source, and an optical section that optically controls the light from the first light source and the second light source and irradiates it toward an object, the optical section comprising an aperture diaphragm that selectively transmits light emitted from the light source section, a pre-lens that transmits the light transmitted through the aperture diaphragm in a divergent state, an irradiation lens that optically controls and emits the light transmitted through the pre-lens, and an outer lens that emits the light emitted from the irradiation lens in a diffuse state. [Claim 8] The illumination device according to claim 7, wherein the aperture diaphragm selectively transmits white light emitted from the first light source. [Claim 9] The illumination device according to claim 1, wherein the light emission control unit comprises a signal generation unit that generates a desired signal, and the waveform control unit, the frequency control unit, the level control unit, and the duty cycle control unit control at least one of the waveform, frequency, level, and duty cycle of the signal generated based on the surrounding conditions of the object. [Claim 10] The lighting device according to any one of claims 1 to 9, wherein the object is a road sign, and the lighting device is arranged to irradiate light toward the road sign.

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