JP6659436B2 - Vehicle lighting method and vehicle lamp - Google Patents

Description

  The present invention relates to a vehicular lighting method and a vehicular lamp, and more particularly to a vehicular lighting method and a vehicular lamp that illuminate the front of a vehicle using a number of light emitting diodes arranged in a planar light emitting region.

  2. Description of the Related Art In recent years, in a vehicle headlamp, a technology (referred to as an ADB adaptive driving beam or the like) for controlling a light distribution shape in real time in accordance with the situation in front, that is, the presence or absence of an oncoming vehicle or a preceding vehicle, and the position thereof has attracted attention. ing. According to this technology, for example, when traveling in a light distribution shape for traveling, that is, a high beam, when an oncoming vehicle is detected, only the light directed to the oncoming vehicle area is irradiated in real time from the area illuminated by the headlight. Can be reduced. It is possible to always provide the driver with a field of view close to the high beam while preventing dazzling light (glare) from being given to oncoming vehicles.

  Further, a headlight system (referred to as an AFS adaptive front-lighting system or the like) that adjusts a light distribution in a traveling direction according to a steering angle of a steering wheel is being generalized. By moving the light distribution shape in the left-right direction according to the steering angle of the steering wheel, the field of view in the traveling direction can be widened.

  Such a variable light distribution type headlight system uses, for example, a light emitting diode device in which a large number of light emitting diodes (LED light emitting diodes) are arranged in an array, and conducts / non-conducts (on / off) each light emitting diode. In addition, it can be realized by controlling the input power (and thus the luminance) during conduction in real time.

  An array of a large number of LED chips which are arranged in a matrix and can be independently controlled to be turned on, and a projection lens arranged on an optical path of light emitted from the LED chip array, and a lighting pattern of the LED chip array is provided. There has been proposed a vehicle headlight device configured to form a predetermined light distribution pattern forward by controlling (for example, Japanese Patent Application Laid-Open No. 2013-54849). Hereinafter, the outline of this proposal will be described.

  FIG. 11A is a diagram of a main part of a vehicle headlamp in which a plurality of LEDs 212 are arranged in a matrix on a support substrate 211 having a heat radiating mechanism, and a projection lens 210 is arranged in front, as viewed from the side.

  FIG. 11B is a front view of a state where a plurality of LEDs 212 are arranged in a matrix. An optical system in which a light source including a plurality of LEDs arranged in a matrix (hereinafter, may be referred to as a “matrix LED”) is directed toward the front of a vehicle and a projection lens is disposed in front of the light source is a luminance distribution of the LEDs. Is projected forward.

  FIG. 11C is a block diagram illustrating a schematic configuration of the headlight system. The headlight system 200 includes left and right vehicle headlights 100, a light distribution control unit 102, a front monitoring unit 104, and the like. The vehicle headlamp 100 has a light source including a matrix LED, a projection lens, and a lamp body that houses them.

  The forward monitoring unit 104 to which various sensors such as the on-vehicle camera 108, the radar 110, and the vehicle speed sensor 112 are connected processes the image data acquired from the sensors, and processes the preceding vehicle (an oncoming vehicle or a preceding vehicle) and other bright lights on the road. It detects objects and lane markings (lane marks) and calculates data required for light distribution control, such as their attributes and positions. The calculated data is transmitted to the light distribution control unit 102 and various in-vehicle devices via an in-vehicle LAN or the like.

  The light distribution control unit 102 to which the vehicle speed sensor 112, the steering angle sensor 114, the GPS navigation 116, the headlight switch 118, and the like are connected is connected to the attribute of the on-road luminous object sent from the forward monitoring unit 104 (oncoming vehicle, preceding vehicle The light distribution pattern (luminance distribution) corresponding to the traveling scene is determined based on the vehicle, the reflector, the road lighting), the position (forward, sideways), and the vehicle speed. The light distribution control unit 102 determines the control content (lighting and extinguishing, input power, etc.) of each LED of the matrix LED necessary to realize the light distribution pattern. The driver 120 converts the information on the control amount from the light distribution control unit 102 into commands corresponding to the operations of the driving device and the light distribution control element, and controls them.

  The vehicle headlamp needs to form a luminance distribution in which the luminance is high at the center (the light distribution center) and decreases toward the periphery. In the case of a vehicle headlamp using a semiconductor light emitting element array, it is possible to adjust the luminance by controlling the driving power of each semiconductor light emitting element and to form a desired luminance distribution.

  In order to adjust the luminance, it is conceivable to change the drive current. However, when the drive current is changed, the chromaticity also changes. When the chromaticity in the visual field changes, the observer feels strange. In order to reduce the change in color tone, it has been proposed that the instantaneous driving current value is fixed, the power is adjusted by changing the pulse width, and a luminance distribution is formed (for example, JP-A-2009-224191). When the dot matrix light source includes a pulse lighting section and a DC lighting section, it is taught that the instantaneous driving current value of the element of the DC lighting section is also the same as the instantaneous driving current value of one element of the pulse lighting section.

JP 2013-54849 A JP 2009-224191 A

  It is desirable that the illumination in front of the vehicle be performed with white light having a desired luminance distribution and uniform chromaticity in order to ensure a good view for the driver and to prevent the driver from feeling uncomfortable. It is. The semiconductor white light emitting element generally has a configuration in which a phosphor is mounted on the semiconductor light emitting element, and the luminance can be adjusted by controlling the driving power. The luminous efficiency of a semiconductor light emitting element changes depending on the temperature, and the light conversion efficiency of a mounted phosphor also has temperature dependence. For this reason, the chromaticity of the semiconductor white light emitting element changes depending on the temperature.

  It is desired that the illumination in front of the vehicle forms a luminance distribution that is high at the center and decreases toward the periphery. When the instantaneous drive current value is the same using a semiconductor white light emitting element array, the duty is controlled to form a supplied power distribution. The amount of generated heat is also distributed according to the input power. Heat generation and heat radiation are not uniform in the array plane. Therefore, a temperature distribution is formed. Due to this temperature distribution, a chromaticity distribution is formed in the semiconductor white light emitting element array surface.

  In a headlamp in which a light distribution pattern is formed by projecting a light emission pattern of a semiconductor white light emitting element array with a lens or the like, the chromaticity distribution is also formed in the light distribution pattern by the chromaticity distribution formed in the semiconductor white light emitting element array plane. Is formed. The chromaticity differs within the field of view of the driver, giving the driver a sense of incompatibility.

  An object of the embodiments is to provide a vehicle lighting method and a vehicle lamp capable of forming a desired luminance distribution in a light emitting surface of a semiconductor light emitting device and realizing a light distribution pattern with a small chromaticity distribution even when a temperature distribution is formed. It is to provide.

According to an embodiment of the present invention,
A vehicle lamp including a light source and a control device,
The light source includes a semiconductor light-emitting element array in which a plurality of semiconductor light-emitting elements each having a phosphor light-emitting unit are two-dimensionally arranged,
The control device includes a pulse power supply capable of simultaneously performing pulse height control and pulse width control of a drive current, and the semiconductor light emitting element array forms a luminance distribution that is high at a central portion and decreases toward the periphery in one direction. Thus, while controlling the applied power distribution, it is possible to control the pulse height distribution so as to form a chromaticity distribution that is high at the center of the luminance distribution and decreases toward the periphery.
A vehicular lamp is provided.

  A chromaticity distribution that is low at the center and high toward the periphery formed by a temperature distribution that is high at the center and low toward the periphery based on the luminance distribution. Can be corrected with a chromaticity distribution that decreases toward.

FIG. 1 is a graph showing a desired light distribution pattern in a visual field and its luminance distribution along horizontal and vertical directions. FIG. 2 is a schematic plan view of a light emitting diode (LED) array. FIG. 3 is a graph showing the temperature dependence of the chromaticity of the white LED when driven at the same current density. FIG. 4 is a graph showing the (instantaneous) current density dependence of the chromaticity of the white LED. FIG. 5 is a graph showing an example of a pulse drive waveform. as well as FIG. 6A is a block diagram schematically illustrating a configuration of a vehicle headlight device using a light emitting diode array according to an embodiment, FIG. 6B is a cross-sectional view schematically illustrating a configuration of a light source including an LED array, and FIG. 6 is a chart showing a process for determining a drive current pulse. FIG. 7A is an equivalent circuit diagram schematically showing a configuration of a control circuit of the LED array, and FIG. 7B is a graph schematically showing a relationship between a desired luminance distribution, an instantaneous current density distribution, and a duty distribution of a pulse waveform. FIG. 8 is a graph showing a group of pulse drive current waveforms of the LED array according to the example. FIG. 9 is a schematic plan view showing another configuration example of the light emitting diode array. FIG. 10 is a schematic plan view showing still another configuration example of the light emitting diode array. 11A, 11B, and 11C are a main part side view of a vehicle headlamp, a plan view of a light emitting diode array, and a block diagram of a vehicle headlamp system according to the related art.

LP alignment pattern, LC light distribution center, BPh horizontal luminance distribution,
BPv vertical luminance distribution, H horizontal axis, V vertical axis,
2 light emitting diode, 21 external sensor, 22 in-vehicle sensor,
24 memories, 26 central processing units, 27 lighting circuits,
28 headlight (LED array), 29, 30 LED array,
31, 32 detection unit, 34 heat radiation unit, 36 projection optical unit,
51 pulse power supply,
100 vehicle headlight, 102 light distribution control unit,
104 forward monitoring unit, 108 on-board camera, 110 radar,
112 vehicle speed sensor, 114 steering angle sensor,
116 GPS navigation, 118 Headlight switch,
120 drivers, 200 headlight systems,
210 Projection lens, 211 Support substrate, 212 LED.

  FIG. 1 is a schematic view showing an example of a light distribution pattern desired for a light beam emitted from a vehicle headlamp, in which the luminance is high near the center and decreases toward the periphery. Below the central part of the light distribution pattern LP facing forward, a high luminance light distribution center LC is formed extending in the horizontal direction. In a vehicle headlamp, the light distribution pattern LP generally gradually decreases toward the periphery with the light distribution center LC extending in the horizontal direction as the highest luminance in order to ensure the visibility of the driver at night. Is desirable. The vicinity of the light distribution center LC may be called the center. The brightness distribution BPh parallel to the horizontal (H) axis is shown above the light distribution pattern LP. The maximum brightness is set on the road surface in front, and the brightness decreases as it moves left and right.

  The brightness distribution BPv parallel to the vertical (V) axis at the center of the horizontal axis is shown on the right side of the light distribution pattern LP. The road surface in front is the light distribution center LC having the maximum luminance, and a certain level of luminance is maintained on the road surface. As it goes upward, the brightness drops significantly. Illuminating areas with no objects to be recognized with high brightness wastes energy.

  A semiconductor white light emitting element array can be used as a light source of a vehicle headlamp. For example, a desired luminance distribution is formed by arranging a large number of semiconductor white light emitting elements in a matrix and adjusting the luminance of each semiconductor white light emitting element. The semiconductor white light emitting element has, for example, a phosphor layer that emits yellow light above the surface of a blue light emitting diode, and has a function of emitting white light.

  Although not restrictive, for example, a GaN-based semiconductor light-emitting device disclosed in the column of Examples of Japanese Patent Application Laid-Open No. 2014-232841, proposed in the column of Examples of Japanese Patent Application No. 2014-237442, proposed by the present applicant. GaN-based semiconductor light-emitting devices, such as the GaN-based semiconductor light-emitting devices disclosed in the Examples of Japanese Patent Application No. 2015-84612.

  FIG. 2 is a schematic plan view showing an example of the light emitting diode array 28 in which light emitting diodes are arranged in a matrix. An array 28 in which light-emitting diodes 2 having the same shape are arranged in a matrix (for example, about 8 rows × 30 columns, which is represented by a simplified 5 rows × 13 columns) in a light-emitting area is shown. Five rows of segments A, B, C, D, and E are arranged in a vertical direction, and a light distribution center is formed in a segment D below the center. The light distribution center is located at a position below the geometric center of the field of view and corresponding to the front road surface.

  It is desirable that the light distribution pattern of the vehicular headlamp realizes a luminance distribution as shown in FIG. 1 in which the luminance in front of the driver is the highest luminance, and the luminance decreases as going to the periphery. In order to form the luminance distribution as shown in FIG. 1, the input power at the center is increased, and the input power is reduced toward the periphery. Typically, the input power is controlled by setting the current density to be constant and performing duty control in pulse width modulation or frequency modulation. The input power can be increased by increasing the duty in the central portion, and the input power can be decreased by decreasing the duty in the peripheral portion.

  The amount of heat generated in the central portion is large due to the large amount of input power, and the amount of heat generation decreases as the amount of input power decreases toward the outer periphery. Further, while heat in the central portion of the semiconductor light-emitting element array is unlikely to diffuse in the in-plane direction, in the peripheral portion, the heat is easily diffused to the periphery toward the outer periphery. Therefore, the temperature of the semiconductor light emitting element array is high at the center portion, and decreases at the peripheral portion toward the outer periphery.

  In the example of the calculated temperature distribution, the temperature of the central part (D) is 115 ° C., and the temperature of the peripheral part (A) is 85 ° C. A temperature difference of 30 ° C. is formed between the central part and the peripheral part. When the temperature of the semiconductor light emitting element changes, the chromaticity of light emission changes. When an array is formed by arranging semiconductor light emitting elements of the same size side by side and driven at the same current density, a temperature distribution is formed by a duty distribution, and a chromaticity distribution is generated by the temperature distribution.

  FIG. 3 shows a white LED using a GaN-based semiconductor light emitting device (LED) having an active layer of InGaN and a YAG (yttrium aluminum garnet) as a phosphor wavelength conversion layer, driven by the same drive current. 6 is a graph illustrating an example of a change in chromaticity of light emission of a semiconductor light emitting diode (LED) with respect to a temperature of the semiconductor light emitting diode (LED) in a case where the temperature is changed. The horizontal axis indicates the temperature of the LED in units of ° C., and the vertical axis indicates the chromaticity of light emission from the LED in units of Cx.

  As the horizontal axis moves rightward (temperature rises), the chromaticity on the vertical axis decreases. When the temperature is around 50 ° C., the rate of decrease in chromaticity due to temperature rise is small, but the rate of decrease in chromaticity increases with temperature rise. For example, in a temperature range of 100 ° C. or more, a chromaticity decrease of about 0.001 Cx or more is caused by a temperature rise of 10 ° C. The central part (D) at 115 ° C. has a chromaticity of about 0.3273 Cx, and the peripheral part (A) at 85 ° C. has a chromaticity of about 0.3303 Cx. The central part has a high temperature, low chromaticity and a strong blue tint, and the peripheral part has a low temperature, high chromaticity and a strong yellow tint.

  To reiterate, as shown in FIG. 1, when the luminance is increased at the center of the field of view and the luminance is decreased toward the periphery, it is necessary to increase the input power at the center with the higher luminance. When the input power at the center is increased, the temperature increases and the chromaticity decreases. When the input power decreases toward the periphery, the temperature decreases and the chromaticity increases. A central portion having a high temperature and a low chromaticity has a strong blue tint, and a peripheral portion having a low temperature and a high chromaticity has a strong yellow tint. The formation of the luminance distribution causes a chromaticity distribution (color unevenness) via the temperature distribution.

  The light emission intensity of the semiconductor light emitting element changes depending on the drive current density, and the conversion efficiency of the phosphor changes depending on the excitation light intensity. Therefore, when the drive current density is changed, the chromaticity of the LED emission light changes depending on the drive current density.

FIG. 4 is a graph showing the current density dependence of the chromaticity of LED emission light in the case of a white LED using a GaN-based semiconductor having InGaN as an active layer as a semiconductor light emitting element and using YAG as a wavelength conversion layer. The horizontal axis indicates current density in units (A / cm ² ), and the vertical axis indicates chromaticity in units (Cx). The current density is not an average value within a cycle but an instantaneous current density. As the instantaneous current density increases, the chromaticity tends to decrease. The chromaticity can be adjusted by changing the instantaneous current density.

  Conventionally, the instantaneous drive current density has not been changed in a single semiconductor light emitting element array. Changing the drive current density complicates the configuration of the power supply. A single instantaneous drive current density is employed to simplify the configuration of the power supply. The input power is adjusted by duty control. In this case, a chromaticity distribution occurs as described above.

  FIG. 5 shows examples of various pulse current waveforms generated by the pulse power supply. The four current waveforms P1 to P4 from the top show power control in which the instantaneous current density is fixed and the duty within each cycle is changed according to the conventional method. A waveform P1 indicates a DC drive state in which the current waveform is continuous within a continuous cycle. The duty of the waveform P1 is 100%. In the next waveform P2, the duty of the current waveform is reduced to 80%. In the waveforms P3 and P4, the duty of the current waveform is further reduced to 60% and 40%. When the current density is fixed and the duty is controlled, the applied power is controlled according to the duty, and the luminance is controlled according to the applied power. By controlling the duty of the current pulse, a desired luminance distribution can be realized in the visual field.

  By controlling the input power so as to realize a luminance distribution that gradually decreases from the center to the periphery, a temperature distribution that is higher in the center and gradually decreases toward the periphery in accordance with the input power is formed. Become. When the temperature distribution occurs, the chromaticity changes as shown in FIG. 3, and a low chromaticity distribution is generated in a high temperature central portion and a high chromaticity distribution is generated in a low temperature peripheral portion, giving an uncomfortable feeling to an observer. It is desired to make the chromaticity uniform.

  The brightness of the peripheral portion needs to be lower than the brightness of the central portion, but the current density is not limited. If the current density in the peripheral part is increased, the chromaticity can be reduced as shown in FIG. When the chromaticity is increased by ΔCx due to the temperature distribution, it is considered that the chromaticity can be made uniform by selecting the instantaneous current density at which the chromaticity is decreased by −ΔCx. By adjusting the duty, the luminance can also be adjusted.

  If the current density is increased without changing the duty, the input power is increased and the luminance is increased. However, the duty ratio is increased while increasing the instantaneous current density to the ratio α (> 1) with respect to the waveform at the center. Is lower than the ratio β (<1 / α), the input power is (α * β) <[α * (1 / α)] = 1, which can be lower than the input power at the center.

  The remaining two current waveforms PH1 and PH2 in FIG. 5 have the instantaneous current densities of the current waveforms P1 to P4 increased by 50% and 100%, respectively. The duties of the waveforms PH1 and PH2 correspond to 100% and 50% of the duty of the waveform P4, and approximately 2/3 and 1/3 of the duty of the waveform P3. The supplied power of the waveform P3 and the waveform PH1 are substantially equal, and the supplied power of the waveform P4 and the waveform PH2 are substantially equal. Even if the instantaneous current density is increased, the supply power can be kept at a predetermined value by reducing the duty. Hereinafter, a vehicle lighting method and a vehicle lamp (headlamp) according to embodiments will be described.

  FIG. 6A is a block diagram schematically illustrating a configuration of a vehicle headlamp according to the embodiment. The external sensor 21 includes a camera, a radar, and the like, and mainly captures information on a preceding vehicle, an oncoming vehicle, and the like, and the detection unit 31 detects information on a preceding vehicle such as an oncoming vehicle, a preceding vehicle. The in-vehicle sensor 22 takes in own-vehicle signals such as an own-vehicle speed signal and a steering angle signal from signal wiring and the like in the vehicle, and the detection unit 32 detects own-vehicle information. The memory 24 includes a read-only memory (ROM), a random access memory (RAM), and the like, and stores information necessary for controlling the headlight system, such as characteristics of a headlamp, external conditions, and the like. The lighting circuits 27A and 27B supply pulse power for driving the headlights 28A and 28B. Each of the headlights 28A and 28B includes a semiconductor light emitting diode (LED) array.

  The central processing unit (CPU) 26 is based on information such as the standard of the LED array, information such as a desirable luminance distribution, and information on the external environment and the like supplied from the detection units 31 and 32, which are supplied from the memory 24. Various calculations are performed to determine drive current pulses for driving the headlights 28A and 28B. The central processing unit 26 can perform ADB for suppressing the light heading for the oncoming vehicle based on the preceding vehicle information and the like, and increase the illumination light to the area to be moved based on the own vehicle signal and the like. AFS can be performed.

  FIG. 6B schematically shows a configuration of a mounting portion of the LED array 28. The LED array 28 is supported by the heat radiating unit 34 and projects the emitted light to the front of the vehicle via a projection optical unit 36 such as a reflector or a lens.

  FIG. 6C is a chart showing a drive current pulse determination process mainly performed by the CPU 26. First, in step S1, information such as element distribution and light emission characteristics of a semiconductor light emitting element (LED) array of a headlight is set. In the following step S2, a desired luminance distribution to be formed in the LED array is set.

  In step S3, a temperature distribution generated by the luminance distribution is calculated. In step S4, an instantaneous current density distribution that minimizes the chromaticity distribution in the temperature distribution is calculated. In step S5, a duty distribution for realizing the luminance distribution in the instantaneous current density distribution is calculated.

  In step S6, the semiconductor light emitting element array is driven by a current pulse having the instantaneous current density obtained in step S4 and the duty obtained in step S5.

  The luminance distribution in step S2 is formed, and the instantaneous current density obtained in step S4 makes the chromaticity uniform. By suppressing the chromaticity distribution in the visual field, the sense of discomfort experienced by the observer is reduced.

  Note that the above steps are performed each time by the built-in CPU 26, and are not limited to being reflected in element driving, but may be reflected in element driving by calling up previously calculated data.

  FIG. 7A is an equivalent circuit diagram schematically illustrating a configuration example of a driving circuit of the LED array. This is a combination of the lighting circuit 27 and the headlight 28 in FIG. 6A. The five rows of LEDs A, B, C, D, and E are arranged side by side in the vertical direction to form a plurality of light emitting diode rows LEDC. In the light emitting diode row LEDC including five rows of LEDs, the cathodes are commonly connected, and the common cathode is connected to the common ground plane GR via the switch SW2. The pulse power supply 51 supplies pulse currents A1, A2, A3, A4, and A5 that can control both the pulse height (instantaneous current density) and the pulse width (duty). The ground terminal of the pulse power supply 51 is connected to the common ground plane GR. The anodes of the five rows of LEDs A, B, C, D, and E are independently drawn out of each row, and the desired instantaneous current density and the desired current density are supplied to the respective light emitting diode columns LEDC of the LED array from separate pulse power supplies in the pulse power supply 51. A duty-given current pulse can be supplied.

  FIG. 7B is a graph schematically showing a relationship between a desired luminance distribution BP, an instantaneous current density IJ for realizing this luminance distribution, and a pulse current duty DT along the vertical direction. First, a luminance distribution BP of a desired pattern that is higher at the center of the visual field and lower as it goes up and down is set. The product of the instantaneous current density IJ and the duty DT determines the input power, and the input power determines the luminance.

  A temperature distribution is formed by the applied power distribution corresponding to the luminance distribution, and a chromaticity distribution accompanying the temperature distribution is generated. In order to correct the chromaticity distribution due to the temperature distribution, the instantaneous current density IJ of the pulse current is set to be the lowest at the center of the visual field and higher toward the periphery. At the center, the chromaticity is increased by setting the instantaneous current density IJ to be low (see FIG. 4), and the tendency that the chromaticity is lowered based on the high temperature (see FIG. 3) can be offset. In the peripheral portion, the chromaticity is reduced by setting the instantaneous current density IJ to be high (see FIG. 4), and the tendency that the chromaticity is increased based on the low temperature (see FIG. 3) can be offset.

  The duty DT for realizing the desired luminance BP is obtained by multiplying the thus obtained instantaneous current density IJ. The product of the instantaneous current density IJ and the duty DT corresponds to the luminance BP.

  As shown in FIG. 7B, in order to multiply the instantaneous current density IJ of the pattern that increases toward the peripheral portion to realize the distribution of the luminance BP of the pattern that decreases toward the peripheral portion, the duty DT of the pulse current The distribution becomes a pattern that decreases toward the periphery with a larger attenuation rate than the distribution of the luminance BP. This embodiment is characterized by a duty distribution that decreases at a larger attenuation rate than a luminance distribution that gradually decreases from the center to the periphery.

  FIG. 8 is a graph showing instantaneous current density waveforms PA, PB, PC, PD, and PE supplied from the pulse power supply 51 to the light-emitting diode array LEDC together with a comparative example. As an example, an instantaneous current density waveform supplied to the LEDs in the five rows A, B, C, D, and E shown in FIG. 2 is shown.

  The waveform according to the example is indicated by a solid line, and the waveform according to the comparative example is indicated by a broken line. In the comparative example, the instantaneous current density is fixed, and in the example, the instantaneous current density is changed to suppress the change in chromaticity. The supply power is controlled so as to form a luminance distribution, and the LED in row D has the highest temperature of 115 ° C., the LED in row A has the lowest temperature of 85 ° C., and the LEDs in row C and row E which are adjacent to row D. It is assumed that the LED reaches 105 ° C. and the LED in row B reaches 95 ° C.

  According to the embodiment, as compared with the instantaneous current density with respect to the center, the instantaneous current density is increased toward the peripheral portion so as to compensate for the increase in chromaticity due to the temperature decrease, and a desired luminance reduction is realized. , The duty is shortened.

  Compared with the instantaneous current density waveform of the comparative example indicated by the broken line, the instantaneous current density IJ is high and the duty is short except for the waveform PD. The driving power is the same as in the comparative example. The instantaneous current density waveform PD for the central LED is the same as the instantaneous current density waveform of the comparative example. The instantaneous current density waveforms in the peripheral portion other than the central portion have a higher current density IJ than the instantaneous current density waveform of the comparative example, have a narrower (shorter) duty, and make the chromaticity uniform while supplying the same power.

  In FIG. 8, the instantaneous current density in the peripheral portion (row A) is corrected to correct the chromaticity difference caused by the temperature drop of about 30 ° C. in the peripheral portion (row A) with respect to the central portion (row D). , 1.7 times (the instantaneous current density of the D row). The current density in row A is multiplied by 1.7, and the chromaticity is shifted by -0.003 Cx, so that the uniformity of the chromaticity distribution of the entire array is improved. The temperature in row B is about 20 ° C. lower than the temperature in row D, and the chromaticity difference is 0.0022 Cx. The instantaneous current density of row B is set to 1.3 times (the instantaneous current density of row D), and the chromaticity is corrected by -0.0022Cx. The temperatures of rows C and E are about 10 ° C. lower than the temperature of row D, resulting in a chromaticity difference of 0.0012 Cx. The instantaneous current densities of rows C and E are set to 1.1 times (the instantaneous current densities of row D), and the chromaticity is corrected by -0.0012 Cx.

  In the above embodiment, each light emitting element of the LED array 28 has the same size. In practice, high resolution is desired at the center of the field of view, but usually high resolution is not required at the periphery of the field of view. For example, a problem hardly occurs even if the resolution of the upper region in the field of view is rather coarse. The distribution of the light emitting elements included in the LED array can be appropriately simplified.

  FIG. 9 is a plan view schematically showing an LED array 29 in which the size of the LEDs 2 in the upper and lower peripheral portions is increased. The row D provided with the horizontal axis H forms the center of the visual field. The height of row D is the smallest, and the heights of rows C and E above and below it are slightly increased. The height of row B above row C has clearly increased, and the height of row A further above has increased significantly. By keeping the density of the light emitting elements at the center of the field of view high, a desired resolution is realized, and the number of elements can be suppressed by increasing the height of the peripheral elements. Note that the horizontal dimension of the LED array was kept constant in consideration of the possibility of executing AFS.

  FIG. 10 is a plan view schematically showing the LED array 30 in which the resolution of the peripheral part is reduced also in the horizontal direction. The number of rows in the vertical direction is maintained at 5, but the number of columns in the horizontal direction is reduced to 11, and the horizontal width of the elements at the left and right peripheral portions is increased. The resolution at the periphery of the visual field can be reduced while maintaining the required resolution at the center of the visual field. The structure and the control can be simplified.

  Although the embodiments have been described above, these do not limit the present invention. In the process shown in FIG. 6C, it has been described that the input power distribution, the temperature distribution, the chromaticity distribution, the instantaneous current density distribution, and the like are calculated. However, a sample is created and actually measured, It is also possible to use both.

  For example, the characteristics of the semiconductor light emitting element array in step S1 may be characteristics measured by preparing a sample. A plurality of samples having different configurations of the heat radiating section may be manufactured. Once the instantaneous current density distribution and the duty distribution are obtained in steps S1 to S6, the chromaticity distribution is measured by driving the light emitting element array, and the instantaneous current density distribution desired to further uniform the obtained chromaticity distribution is obtained. The duty distribution may be calculated and corrected based on the corrected instantaneous current density distribution. These may be further repeated.

  Further, a plurality of power supplies having different instantaneous current amounts may be used. For example, in a semiconductor light emitting element array as shown in FIGS. 2, 9, and 10, rows A and B use a power source having a relatively high instantaneous current amount, and rows C, D and E have a power source having a relatively low instantaneous current amount. Is used. Then, a duty distribution for achieving a desired luminance distribution is calculated. In contrast to the tendency that the luminance at the element center (included in rows C, D, and E) is high and the luminance decreases as it goes to the periphery, chromaticity variation can be reduced even with such a configuration. Note that the luminance distribution may be changed depending on the driving situation. For example, when approaching a curve, the luminance center is moved in a turning direction. In this case, the luminance center largely moves in the irradiation horizontal direction, and there is no significant change in the vertical direction. Therefore, it is preferable that different power supplies be controlled in different rows in the vertical direction of illumination of the lamp.

  Numerical values and materials used in the description are examples, and are not limiting. Various changes, substitutions, etc. may be made according to the required characteristics. Known equivalents may be substituted. For example, a light emitting diode (LED) may be a semiconductor laser. Since a semiconductor laser is also a diode, the concept of an LED includes a laser. It will be apparent to those skilled in the art that various other modifications, improvements, combinations, and the like can be made.

Claims (13)

A plurality of semiconductor light emitting elements each having a phosphor light emitting section are two-dimensionally arranged, and it is desired to realize a semiconductor light emitting element array constituting a vehicle headlamp and to be realized in the semiconductor light emitting element array plane. Set the brightness distribution,
A semiconductor light emitting element array using a pulse current having an instantaneous current density distribution that at least partially cancels a chromaticity distribution derived from a temperature distribution generated by the luminance distribution, and a duty distribution that realizes the luminance distribution in the instantaneous current density distribution Driving the
Vehicle lighting method.
2. The instantaneous current density distribution according to claim 1, wherein a driving pulse of a semiconductor light emitting element having a low luminance in the luminance distribution is formed to have a pulse height higher than a driving pulse of a semiconductor light emitting element having a relatively high luminance. Vehicle lighting method.
The luminance distribution gradually attenuates from the luminance center having the highest luminance toward the peripheral portion in one direction, and the duty distribution gradually attenuates from the luminance center to the peripheral portion at a larger attenuation rate than the luminance distribution. The vehicle lighting method according to claim 2.
The semiconductor light-emitting element array according to claim 1, wherein the semiconductor light-emitting elements have an arrangement in which the semiconductor light-emitting elements are arranged in a matrix along the horizontal and vertical directions of the outside world, and have a luminance distribution along the vertical direction. Item 4. The vehicle lighting method according to item 1.
A vehicle lamp including a light source and a control device,
The light source includes a semiconductor light-emitting element array in which a plurality of semiconductor light-emitting elements each having a phosphor light-emitting unit are two-dimensionally arranged,
The control device includes a pulse power supply that can simultaneously perform pulse height control and pulse width control of a drive current, and the semiconductor light emitting element array forms a luminance distribution that is high at a central portion and decreases toward the periphery in one direction. Thus, while controlling the applied power distribution, the pulse height distribution can be controlled so as to form a chromaticity distribution that is high at the center of the luminance distribution and decreases toward the periphery.
Vehicle lighting fixtures.
The control device can form, in the one direction, a luminance distribution that attenuates gradually from a central portion to a peripheral portion, and a duty distribution that attenuates from the central portion to the peripheral portion at a larger attenuation rate than the luminance distribution. The vehicular lamp according to claim 5.
7. The vehicular vehicle according to claim 5, wherein the semiconductor light emitting element array has an arrangement in which semiconductor light emitting elements are arranged in a matrix along an external horizontal and vertical direction, and the one direction is a vertical direction. 8. Lights.
The vehicular lamp according to any one of claims 5 to 7, wherein the plurality of semiconductor light-emitting elements have a GaN-based active layer and a YAG-based phosphor light-emitting portion.
The vehicle according to any one of claims 5 to 8, wherein in the plurality of semiconductor light emitting elements of the semiconductor light emitting element array, in the one direction, a peripheral semiconductor light emitting element has a larger area than a central semiconductor light emitting element. Lighting fixtures.
9. The sensor according to claim 5, further comprising a sensor that monitors a front direction, wherein the control device can control driving power supplied to the plurality of semiconductor light emitting elements based on a signal from the sensor. 4. The vehicle lighting device according to claim 1.
A vehicle lamp including a light source and a control device,
The light source includes a semiconductor light-emitting element array in which a plurality of semiconductor light-emitting elements each having a phosphor light-emitting unit are two-dimensionally arranged,
The control device includes a pulse power supply capable of performing pulse width control, and controls a supplied power distribution such that the semiconductor light emitting element array forms a luminance distribution that is high in a central portion and decreases toward the periphery in one direction. While forming a low pulse height at the center of the luminance distribution and a high pulse height at the periphery,
Vehicle lighting fixtures.
The control device has a plurality of power supplies having different pulse heights,
The pulse supplied by the plurality of power supplies has a higher pulse height at the periphery of the luminance distribution than at the center.
The vehicular lamp according to claim 11.
  13. The vehicular lamp according to claim 11, wherein the one direction forming the luminance distribution is an orientation direction irradiated in a vertical direction.

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