JP6935536B2 - Vehicle lighting - Google Patents

Description

The present invention relates to a vehicle lamp, and more particularly to a vehicle lamp including a large number of light emitting diodes arranged in a planar light emitting region.

In recent years, in vehicle headlights, a technique (called ADB adaptive driving beam, etc.) that controls the light distribution shape in real time according to the situation in front, that is, the presence or absence of an oncoming vehicle, a vehicle in front, and the position thereof, has attracted attention. ing. According to this technology, for example, when an oncoming vehicle is detected while traveling with a light distribution shape for traveling, that is, a high beam, only the light directed to the area of the oncoming vehicle is detected in real time in the area irradiated by the headlights. Can be reduced with. It is possible to always give the driver a field of view close to that of a high beam, while preventing glare from being given to an oncoming vehicle.

Further, a headlight system (called an AFS adaptive front-lighting system or the like) that adjusts the light distribution in the traveling direction according to the steering angle of the steering wheel is becoming 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.

In such a variable light distribution type headlight system, for example, a light emitting diode device in which a large number of light emitting diodes (LEDs) are arranged side by side in an array is created, and each light emitting diode conducts / does not conduct (on / off) and conducts. This can be achieved by controlling the input current (and therefore the brightness) of the hour in real time.

A large number of LED chip arrays arranged in a matrix and independently controllable for lighting and a projection lens arranged on an optical path of light emitted from the LED chip array are provided, and the lighting pattern of the LED chip array is determined. A vehicle headlight device configured to form a predetermined light distribution pattern forward by controlling has been proposed (for example, Japanese Patent Application Laid-Open No. 2013-54849).

FIG. 11A is a side view of a main part of a vehicle headlight in which a plurality of light emitting diodes (LEDs) 212 are arranged in a matrix on a support substrate 211 having a heat dissipation mechanism and a projection lens 210 is arranged in front. Is.

FIG. 11B is a schematic view of a state in which a plurality of LEDs 212 are arranged in a matrix as viewed from the front. An optical system in which a light source composed of a plurality of LEDs arranged in a matrix (hereinafter, may be referred to as “matrix LED”) is directed toward the front of the vehicle and a projection lens is arranged in front of the light source makes the brightness distribution of the LEDs forward. Project to.

FIG. 11C is a block diagram showing 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 headlight 100 includes a light source composed of matrix LEDs, a projection lens, and a lamp body for accommodating them.

The front monitoring unit 104, to which various sensors such as the in-vehicle camera 108, the radar 110, and the vehicle speed sensor 112 are connected, processes the imaged data acquired from the sensors and performs image processing on the vehicle in front (oncoming vehicle or preceding vehicle) or other road brilliance. Detects objects and lane markings, 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 the 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, etc. are connected is an attribute of a bright object on the road (oncoming vehicle, preceding vehicle) sent from the front monitoring unit 104. Based on the vehicle, reflector, road lighting), its position (front, side), and vehicle speed, the light distribution pattern corresponding to the driving scene is determined. The light distribution control unit 102 determines the control amount of the light distribution variable headlight required to realize the light distribution pattern.

The light distribution control unit 102 determines the control content (turning on / off, input power, etc.) of each LED of the matrix LED. 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 drive device and the light distribution control element, and controls them.

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

Japanese Unexamined Patent Publication No. 2013-54849

In a semiconductor light emitting device, the light conversion efficiency of the mounted phosphor is also temperature-dependent. Therefore, the chromaticity of the semiconductor light emitting device changes depending on the temperature. When a semiconductor light emitting device array is used as a light source for a head lamp, if a brightness distribution that is high in the center and decreases toward the periphery is formed, heat generation and heat dissipation are not uniform in the array surface, so that a temperature distribution is formed. This temperature distribution causes a chromaticity distribution to be formed in the surface of the semiconductor light emitting device array.

In a head lamp that forms a light distribution pattern by projecting the light emission pattern of the semiconductor light emitting element array with a lens or the like, the color distribution pattern also has a chromaticity distribution due to the chromaticity distribution formed in the surface of the semiconductor light emitting element array. It will be formed. If the chromaticity is different within the driver's field of view, the driver will feel uncomfortable.

An object of the embodiment is to provide a vehicle lamp capable of realizing a light distribution pattern having a small chromaticity distribution even if a change in brightness is formed in the surface of the semiconductor light emitting device.

According to the examples of the present invention
Including light source and control device
The light source is composed of a semiconductor light emitting element array including a group of semiconductor light emitting elements in which a plurality of semiconductor light emitting elements each having a phosphor emitting unit are arranged side by side in the first direction.
The control device is
In the semiconductor light emitting element group, a brightness distribution having a high-luminance portion having a relatively high brightness and a low-luminance portion having a relatively low brightness is formed.
A vehicle lighting tool for controlling the drive current density of the semiconductor light emitting device in the high-luminance portion to be lower than the drive current density of the semiconductor light-emitting element in the low-luminance portion is provided.

The chromaticity distribution formed by the temperature distribution based on the luminance distribution can be corrected by the current density distribution.

FIG. 1A is a cross-sectional view showing a cross-sectional structure of a semiconductor light emitting device, and FIG. 1B is a graph of a desired light distribution pattern in a visual field and a luminance distribution along the horizontal and vertical directions thereof. FIG. 2 is a schematic plan view of a light emitting diode (LED) array. 3A and 3B are graphs showing the relationship between the LED temperature and the chromaticity of LED light emission with respect to the current density. FIG. 4A is a graph showing a simplified distribution of luminance distribution along one direction, FIG. 4B is a graph showing a simplified distribution of chromaticity α along one direction generated based on the luminance distribution of FIG. 4A, and FIG. 4C is a graph showing simplified distribution. A graph showing a simplified current density distribution along one direction, FIG. 4D is a graph showing a simplified distribution of chromaticity β along one direction generated based on the current density distribution of FIG. 4C, and FIG. 4E is FIG. 4B. It is a graph which shows roughly the distribution along one direction of the composite chromaticity which combined the chromaticity α shown in FIG. 4D and the chromaticity β shown in FIG. 4D. 5A and 5B are circuit diagrams schematically showing a wiring example of a semiconductor light emitting element array and a current source for five semiconductor light emitting elements in one row, and FIG. 5C shows a power supply waveform Wp in the central portion and a supply in the peripheral portion. It is a graph which shows the example of the power waveform Wt. 6A and 6B are a schematic plan view showing a distribution example in which the area of the light emitting diode in the light emitting diode array is chipped from the central portion to the peripheral portion and is reduced, and a circuit diagram showing a wiring example for one row. FIG. 7A is a block diagram schematically showing the configuration of a vehicle headlight device using a light emitting diode array, and FIGS. 7B and 7C are graphs showing the shape of a drive waveform by pulse width modulation and frequency modulation. FIG. 8 is a schematic plan view showing another example of the relative area distribution of the light emitting diodes in the light emitting diode array. FIG. 9 is a graph showing the relationship between the emission brightness of the LED and the drive current density. 10A and 10B are wiring diagrams showing other wiring examples of the light emitting diode array. 11A, 11B, and 11C are a side view of a main part of a vehicle headlight, a plan view of a light emitting diode array, and a block diagram of a vehicle headlight system according to the prior art. FIG. 12 is a wiring diagram showing another wiring example of the light emitting diode array. FIG. 13 is a drawing showing a situation in which a vehicle headlight device using a light emitting diode array illuminates the ground.

LP light distribution pattern, LC light distribution center, BP brightness distribution,
2 light emitting diode, 43 power supply unit,
44 Duty Modulation Control Unit, 45 Camera Unit,
P Light emitting area center, T Light emitting area peripheral part, 100 Vehicle headlights,
102 Light distribution control unit, 104 Front monitoring unit,
108 in-vehicle camera, 110 radar, 112 vehicle speed sensor,
114 rudder angle sensor, 116 GPS navigation,
118 headlight switch, 120 driver, 200 headlight system,
210 projection lens, 211 support board, 212 LED

A semiconductor light emitting device array can be used as a light source for a vehicle headlamp. The semiconductor light emitting device has, for example, a yellow light emitting phosphor layer above the surface of the blue light emitting diode, and has a function of emitting white light. The individual semiconductor light emitting devices constituting the array are not limited, but for example, the GaN-based semiconductor light emitting device disclosed in the column of Examples of Japanese Patent Application No. 2014-237442 proposed by the present inventors is used. Can be done.

FIG. 1A is a cross-sectional structure of a semiconductor light emitting device as an example. Two adjacent elements are shown. Each element 20 is bonded onto the support substrate 12 via the bonding layers 60 and 70. The element 20 is composed of a p-type layer 24, an active layer 23, and an n-type layer 22 from the support substrate 12 side. The light emitting surface of the n-type layer further has a concavo-convex structure layer 25 for extracting light. The bonding layer 60 also functions as an electrode, is electrically connected to the p electrode 30 and the n via electrode 50, and also functions as wiring between adjacent elements. A phosphor layer 80 is further provided on the element 20.

The semiconductor light emitting element array is composed of, for example, a large number of semiconductor light emitting elements arranged in a matrix, and a desired brightness distribution is formed by adjusting the brightness of each semiconductor light emitting element.

FIG. 1B is a schematic view showing an example of a desired light distribution pattern. The light distribution pattern toward the front is shown by LP. The luminance distribution BPh along the horizontal cross section and the luminance distribution BPv along the vertical cross section are shown above and to the right of the LP. In vehicle headlights, in order to secure the driver's field of view at night, the light distribution pattern generally has the maximum brightness of the light distribution center LC extending in the horizontal direction and gradually decreases toward the periphery. Brightness distribution is desirable. The vicinity of the light distribution center is sometimes called the central part.

FIG. 2 is a schematic plan view showing light emitting diode arrays arranged in a matrix. An array in which light emitting diodes 2 having the same shape are arranged in a matrix (for example, about 8 rows × 30 columns; shown in a simplified 5 rows × 11 columns) is shown in the light emitting region. As a headlight for a vehicle, it is desirable to realize a brightness distribution as shown in FIG. 1B, in which the front of the driver has the maximum brightness and the brightness decreases toward the periphery. In order to form the luminance pattern as shown in FIG. 1B, the input power of the central portion P is increased, and the input power of the peripheral portion T is decreased toward the periphery.

Since the input power is large in the central part, the amount of heat generated is large, and the amount of heat generated decreases toward the outer periphery. Further, while the heat in the central portion P of the semiconductor light emitting device array is difficult to diffuse in the in-plane direction, the heat in the peripheral portion T becomes easier to diffuse toward the outer periphery. Therefore, in the semiconductor light emitting device array, the temperature of the central portion P is high, and the temperature of the peripheral portion T decreases toward the outer periphery. In the example of the calculated temperature distribution, the temperature of the central portion P is 115 ° C. and the temperature of the peripheral portion T is 85 ° C. A temperature difference of 30 ° C. is formed between the central portion P and the peripheral portion T.

FIG. 3A shows a semiconductor light emitting diode (LED) in the case of a white LED using a GaN-based semiconductor light emitting device (LED) having InGaN as an active layer and using YAG (yttrium aluminum garnet) as a phosphor wavelength conversion layer. It is a graph which shows the example of the change of the chromaticity of the light emission of LED with respect to the temperature of. The current density is constant. The horizontal axis indicates the temperature of the LED in the unit ° C., and the vertical axis indicates the chromaticity of the light emitted from the LED in the unit Cx.

As the temperature rises, the chromaticity tends to decrease. When the temperature is around 50 ° C., the temperature change of the chromaticity is small, but as the temperature rises, the rate of decrease in the chromaticity due to the temperature increases. When the temperature of the LED reaches 85 ° C. at the T point in the peripheral portion and 115 ° C. at the P point in the central portion, it will be distributed between PTs at 30 ° C. Due to this temperature difference, the chromaticity is reduced by about 0.003 Cx from about 0.3303 Cx in the peripheral portion T to about 0.3272 Cx in the central portion P. Comparing the central portion and the peripheral portion, the central portion has a high temperature and a low chromaticity and a strong bluish tint, and the peripheral portion has a low temperature and a high chromaticity and a strong yellow tint.

To reiterate, when the brightness is increased at the central portion of the visual field and the brightness is decreased toward the peripheral portion as shown in FIG. 1B, it is necessary to increase the input power at the central portion having high brightness. When the power input to the central part is increased, the temperature rises and the chromaticity decreases. Comparing the central portion and the peripheral portion, the central portion having a high temperature and a low chromaticity has a strong bluish tint, and the 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).

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

The present inventors have investigated the possibility of realizing a light distribution pattern with a small chromaticity distribution. It is considered an indispensable requirement to make the brightness in the central part of the visual field higher than that in the peripheral part. In order to increase the brightness of the central portion, it is necessary to supply high driving power, and the amount of heat generated is inevitably high. The temperature in the central part becomes higher, the chromaticity in the central part becomes lower than that in the peripheral part, and the bluish tint becomes stronger.

FIG. 3B is a graph showing the current density dependence of the LED emission chromaticity in the case of a white LED using a GaN-based semiconductor having InGaN as an active layer as the semiconductor light emitting device and YAG as the wavelength conversion layer. The temperature is constant. The horizontal axis indicates the current density in units (A / cm ² ), and the vertical axis indicates the chromaticity in units (Cx). As the current density increases, the chromaticity decreases. The rate of decrease in chromaticity due to the increase in current density tends to decrease as the current density increases.

The brightness of the peripheral portion needs to be lower than the brightness of the central portion, but the drive current density is not limited. The tendency for the chromaticity to decrease in the central part due to the formation of the luminance distribution can be compensated for by lowering the drive current density in the central part and increasing the chromaticity.

FIG. 4A is a graph showing, for example, a simplified luminance distribution with respect to a position along one direction (for example, the vertical (vertical) direction) of the in-plane luminance distribution shown in FIG. 1B. It is assumed that the vertical axis indicates the distance R from the center portion and the luminance center is located at the position of the horizontal axis. The horizontal axis shows the brightness. The brightness is high in the central part, and the brightness gradually decreases toward the periphery in the peripheral part. Here, the current density is constant.

FIG. 4B is a graph schematically showing the distribution of the chromaticity α along the one direction based on the incidentally generated temperature distribution when the luminance distribution shown in FIG. 4A is formed. The vertical axis represents the distance R from the center, and the horizontal axis represents the chromaticity α. Due to the high power supply, the center of brightness becomes high in temperature and the chromaticity becomes low. The temperature of the peripheral portion decreases toward the periphery, and the chromaticity increases.

FIG. 4C is a graph schematically showing an example of a change in the drive current density of the semiconductor light emitting device with respect to the position along the one direction. The drive current density is lowered in the central part, and the drive current density is increased toward the peripheral part. Here, the temperature is constant.

FIG. 4D is a graph schematically showing the distribution of chromaticity β along the one direction caused by the change in current density shown in FIG. 4C. The current density increases and the chromaticity decreases from the central portion to the peripheral portion.

FIG. 4E is a graph schematically showing a change in the composite chromaticity obtained by combining the chromaticity α shown in FIG. 4B and the chromaticity β shown in FIG. 4D with respect to the position along the one direction. That is, it is a graph when both the current density and the temperature are changing. It can be seen that the change in chromaticity α accompanying the formation of the luminance distribution is significantly reduced by the coalescence of chromaticity β accompanying the current density distribution.

When a plurality of driving elements are driven with the same current density, the chromaticity generated by the driving currents is the same, but the chromaticity can be changed by changing the driving current density. The actual chromaticity distribution is the sum of the chromaticity α in FIG. 4B and the chromaticity β in FIG. 4D, and the chromaticity distribution in FIG. 4B caused by the temperature distribution is the chromaticity distribution in FIG. 4D due to the change in current density. At least part of it can be canceled.

In order to form the luminance distribution, it is necessary to make the power supply in the peripheral portion smaller than the power supply in the central portion. Normally, the current density is increased in order to increase the brightness, but in the present application, in consideration of the above circumstances, the current density in the peripheral portion is made higher than the current density in the central portion, and at the same time, the power supply in the peripheral portion is increased. No measures were taken.

FIG. 5A is a circuit diagram schematically showing a wiring example of a semiconductor light emitting element array, FIG. 5B is a circuit diagram showing five current sources for five semiconductor light emitting elements in one row, and FIG. 5C is a central portion. It is a graph which shows the example of the supply power waveform Wp and the supply power waveform Wt of the peripheral part. As shown in FIG. 2, it is assumed that semiconductor light emitting devices having the same shape are arranged in a matrix.

In FIG. 5A, the cathodes of the five light emitting diodes D1, D2, D3, D4, and D5 arranged in the column direction are connected to the common cathode wiring K, and the anodes A1, A2, A3, A4, and A5 are individually wired. There is. As shown in FIG. 5B, for example, independently controllable current sources are connected to each of these five anodes A1 to A5.

The upper part of FIG. 5C is a graph showing the power supply Wp to the semiconductor light emitting element in the central portion, and the lower part is a graph showing the power supply Wt to the semiconductor light emitting element in the peripheral portion. The power supply in the central part is performed in most of the cycle (may be continuous supply), while the power supply in the peripheral part is performed only in a part of the cycle, for example, about 1/4. Even if the instantaneous power supply in the peripheral portion is about twice the instantaneous power supply in the central portion, the power supply in the cycle can be reduced to 60% or less.

Various methods are conceivable for increasing the current density and decreasing the supplied power. In the above example, as in the prior art, the LEDs in the light emitting element array have the same light emitting area, and the drive current source is independent for each semiconductor light emitting element. The current value while the current was being supplied was Wt> Wp, and the semiconductor light emitting element in the peripheral portion was larger, so that the current density was larger in the peripheral portion. However, when considered in one cycle, the semiconductor light emitting element in the peripheral portion has a short current supply time, and the total power (corresponding to the volume of the current ON in the drawing) is smaller than that of the semiconductor light emitting element in the central portion. As a result, the brightness of the central portion is high and the current density is lower than that of the peripheral portion.

The current value indicates the amount of current applied to a single semiconductor light emitting element, and the current density indicates the amount of current per unit area when the applied current spreads in the plane. However, this method complicates the configuration of the current source. Even if the current value is constant, it is conceivable to drive the semiconductor light emitting element with different drive current densities by changing the area of the semiconductor light emitting element. It is possible to simplify the drive circuit.

When the light emitting area of the semiconductor light emitting element is reduced, the current density becomes higher even if the current has the same current value. This is because even if the applied current value is the same, the spread in the surface of the semiconductor light emitting device is different. If the drive current density of the light emitting element in the peripheral part is increased as compared with the central part, the chromaticity in the peripheral part becomes lower, the chromaticity distribution (color unevenness) due to temperature is canceled, and the color unevenness as a whole is improved. Expected to be possible. Of course, in order to enhance the effect of canceling the chromaticity, the area of the semiconductor light emitting element in the peripheral portion may be reduced and the instantaneous input current value may be increased.

FIG. 6A is a plan view schematically showing a configuration example in which the semiconductor light emitting elements constituting the semiconductor light emitting element array change the light emitting area along a predetermined direction. Similar to FIG. 2, the light emitting diode elements 2 having 5 rows and 11 columns are arranged in a matrix. The numerical value displayed in each element indicates the relative light emitting area. The direction of the drawing follows the direction of the irradiation light as a vehicle lamp, not the actual arrangement direction of the semiconductor light emitting element array. That is, the arrangement is shown so that the vertical direction of the drawing is the vertical direction and the left and right directions are the horizontal direction.

Of the five semiconductor light emitting elements 2 in the same row arranged in the vertical V direction, the second element from the bottom has a maximum area of 100%, and the relative areas of the elements above and below the element are reduced to 85%. .. Further, the relative area of the upper element decreases to 75% and 67% as it goes upward. If the same current value is supplied to each element, the current density is proportional to the inverse of the area. Therefore, the drive current density of the semiconductor light emitting element in the peripheral portion around the semiconductor light emitting element in the central portion of the maximum area is the semiconductor in the central portion. The drive current densities of the light emitting elements are 100/85, 100/75, and 100/67. The drive current density has increased to about 50%. The elements in the same row arranged in the horizontal H direction have the same light emitting area.

FIG. 6B is a wiring diagram showing a circuit example of one row of semiconductor light emitting elements. A series connection of the light emitting diodes D1, D2, D3, D4, D5 is connected between the constant current source CC and the cathode K. When the series connection is driven by the drive current from the constant current source CC, the drive current densities in the diodes D1, D2, D3, D4, D5 are 100/67, 100/75, 100/85, 100/100 = 1, The ratio is 100/85. Since the current density increases from the central portion to the periphery of the peripheral portion, the chromaticity decreases and the peripheral portion becomes more bluish. For example, increasing the drive current density by about 50% reduces the chromaticity by about 0.002. Based on the brightness distribution, the chromaticity distribution that increases toward the periphery is compensated to make the chromaticity uniform.

In the circuit of FIG. 6B, the series connection of the switches SW1, SW2, SW3, SW4, SW5 is connected in parallel with the series connection of the diodes D1, D2, D3, D4, D5, and the intermediate terminals are also connected to each other. That is, the switches SW1, SW2, SW3, SW4, SW5 are connected in parallel with the diodes D1, D2, D3, D4, D5. When the switch SW3 is short-circuited, the diode D3 is short-circuited, and the light emitting state changes to the non-light emitting state. By setting an arbitrary light emitting diode to a non-light emitting state, fine ADB control becomes possible. The connection of the switch to the light emitting diode having low brightness in the peripheral portion may be omitted.

In order to maintain the desired brightness distribution, the power supply in the peripheral portion needs to be a predetermined value smaller than the power supply in the central portion. For example, the power supply of the central portion D4 is continuous direct current (100%), and the drive currents for the elements (D3, D5), D2, and D1 are duty-modulated to be 85%, 75%, 67%, and so on. The power supply is reduced from the part to the periphery.

FIG. 7A is a block diagram schematically showing the configuration of a vehicle headlight device using a light emitting diode array. The lens unit 42 is arranged in front of the light emitting diode array 41, and emits light from the light emitting diode array in the front. The power supply unit 43 supplies a modulation-controlled drive current to the light emitting diode array via the duty modulation control unit 44. The camera unit 45 forms an image of the front of the vehicle and supplies information on the oncoming vehicle, the vehicle in front, and the like to the duty modulation control unit 44. The duty modulation control unit 44 performs modulation control drive by pulse width modulation or frequency modulation, and also performs light emission stop processing in a specific direction.

FIG. 7B shows a change in the drive waveform due to pulse width modulation. From the top, the drive waveforms of duty 10%, 20%, and 50% are shown. The current value during charging is constant.

FIG. 7C shows a change in the drive waveform due to frequency modulation. From the top, the drive waveforms of duty 10%, 20%, and 50% are shown. The number of pulses within a fixed cycle is modulated. The light emitting diode is driven at a portion that overlaps with the voltage application of each time-division row.

FIG. 8 is a plan view showing another example of the area ratio of the light emitting diode elements distributed in the light emitting diode array. In the configuration of FIG. 6A, the light emitting area ratio of the elements arranged in the vertical direction corresponding to the row of the matrix is set to 100% for the element D4 in the central portion, and 85% for (D3, D5) and D2 toward the periphery. 75% and D1 67%, and element rows having the same configuration were arranged at equal pitches in the horizontal direction corresponding to the rows of the matrix. The center position in the horizontal direction can be freely selected, and the configuration is suitable for performing AFS. The brightness distribution in the horizontal direction is performed by modulating the supply current.

In the configuration of FIG. 8, the light emitting area is also changed in the horizontal direction, and it becomes easy to form a luminance distribution that is high in the central portion and decreases toward the periphery. The light emitting area of the element train along the vertical axis V is the same as that of FIG. 6, but the ratio decreases as the distance from the left and right increases. The area ratio of the leftmost column is slightly smaller than the area ratio of the rightmost column, enabling more appropriate settings for a configuration in which two headlights are arranged on the left and right sides of the front end of the vehicle. The control of the duty modulation control unit 44 shown in FIG. 7A is a two-dimensional control.

As described above, the duty ratio is adjusted to adjust the brightness distribution. Here, the luminous efficiency of the semiconductor light emitting device has a characteristic that it decreases as the injection current density increases.

FIG. 9 is a graph showing the current density dependence of luminance. Luminance tends to saturate as the current density increases. Considering this characteristic, it is preferable to finely adjust the product of the light emitting area and the current density of the semiconductor light emitting element in the peripheral portion. For example, it would be preferable to prototype the sample and optimize the design so that more favorable properties can be achieved.

10A and 10B are configurations in which a plurality of light emitting elements are simultaneously controlled in a peripheral portion that does not necessarily require a fine resolution. The top light emitting element D1 in the row and the next light emitting element D2 receive the same control. The drive circuit can be simplified. Further, as shown in FIG. 12, one switch may collectively control a plurality of semiconductor light emitting elements.
Further, when the semiconductor light emitting elements can be individually driven, the brightness distribution thereof can be changed according to the situation by controlling the power supply device. However, in vehicle lamps, the basic light distribution pattern is predetermined, and a light emitting diode array is also formed accordingly. Therefore, optimally, the light emitting diode array is designed so that the semiconductor light emitting element having the highest brightness when reproducing the basic light distribution pattern has the maximum area. As a result, a light emitting diode array in which the area of the semiconductor light emitting element decreases as the distance from the semiconductor light emitting element having the maximum area increases is completed. The smallest element is preferably at one end. Further, in a vehicle lamp, the position of the maximum brightness is preferably a position slightly distant from the end portion while being biased to one side. Therefore, the element having the maximum brightness, in FIGS. 6A and 8, the element having the maximum size is located at the position sandwiched between the elements at both ends in the row direction and the second from the bottom.
Even if the brightness distribution can be changed depending on the situation, there is no change in the tendency that the brightness center is located in the vehicle lamp and the brightness decreases toward the peripheral portion. The appearance of the change in brightness changes. Therefore, there is no difference in that the light emitting diode array has the central portion having the highest brightness, and the brightness becomes smaller toward the peripheral portion. Such control is performed by the duty modulation control unit 44 and the power supply unit 33.

FIG. 13 is a drawing showing a situation in which a vehicle headlight device using a light emitting diode array illuminates the ground. The light emitted from the light emitting diode array illuminates the ground through the lens. Where the light emitting diode array is placed in the lamp is not limited to as shown in the figure. The semiconductor light emitting element having the maximum brightness in the light emitting diode array exists at a position offset to one direction side from the center in the column direction. In the light emitting diode arrays of FIGS. 6A and 8, the semiconductor light emitting element having the maximum brightness and the maximum size is located on the lower side (second from the bottom). When the ground is irradiated, the semiconductor light emitting element in the direction in which the maximum brightness element (maximum size element in FIGS. 6A and 8) is offset (lower element in FIGS. 6A and 8) illuminates the position closest to the lamp. Then, the element on the opposite side (the element on the upper side in FIGS. 6A and 8) irradiates the farthest position. Therefore, the lamp of FIG. 13 is arranged so that the direction in which the maximum brightness element is offset (the direction in which the maximum size element is offset in FIGS. 6A and 8) illuminates near the ground, and the opposite side illuminates far from the ground. Have been placed. If irradiation is performed on a virtual screen perpendicular to the ground, irradiation is performed from the lower elements in FIGS. 6A and 8 on the lower side (ground side) as shown in FIG. 1, and the opposite side is applied to the upper side. Is irradiated from.

As described above, it has been described that a high-luminance element is arranged in the central portion and a lower-luminance element is arranged in the peripheral portion, but in the case of duty drive, the time average brightness is considered. That is, it is the average brightness during one cycle of the drive signal.

As described above, the light emitting diode array controls so that the brightness is high in the center and the brightness decreases toward the peripheral part, and the chromaticity is reduced in the peripheral part under the assumption of a constant temperature. By doing so, the distribution of chromaticity due to the influence of temperature is canceled. As a method of lowering the chromaticity of the peripheral part, there is a method of increasing the current density.

Although described above with reference to Examples, these do not limit the present invention. The numerical values and materials used in the explanation are examples and are not restrictive. A known equivalent may be substituted. For example, the light emitting diode (LED) may be a semiconductor laser. Since a semiconductor laser is also a diode, the concept of LED includes a laser. It will be obvious to those skilled in the art that various other changes, improvements, combinations, etc. are possible.

Claims (9)

Including light source and control device
The light source is composed of a semiconductor light emitting element array including a group of semiconductor light emitting elements in which a plurality of semiconductor light emitting elements each having a phosphor emitting unit are arranged side by side in the first direction.
The control device is
In the semiconductor light emitting element group, a brightness distribution having a high-luminance portion having a relatively high brightness and a low-luminance portion having a relatively low brightness is formed.
A vehicle lamp that controls the drive current density of the semiconductor light emitting device in the high-luminance portion to be lower than the drive current density of the semiconductor light-emitting element in the low-luminance portion. The semiconductor light emitting device group according to claim 1, wherein the high-luminance portion is formed in the central portion in the first direction, and the low-luminance portion is formed around the high-luminance portion. Vehicle lighting equipment. In the semiconductor light emitting element array, a plurality of the semiconductor light emitting element groups forming columns in the first direction are arranged in a second direction perpendicular to the first direction to form a row. The vehicle lamp according to claim 1 or 2, wherein the semiconductor light emitting elements of the above are arranged in a matrix. The vehicle lamp according to any one of claims 1 to 3, wherein the control device collectively controls a plurality of the plurality of semiconductor light emitting elements. The vehicle lamp according to any one of claims 1 to 4, wherein the semiconductor light emitting element array is composed of a plurality of columns and has the same drive current density of the semiconductor light emitting elements in the same row. The vehicle lighting device according to any one of claims 1 to 4, wherein the control device makes the power supplied to the semiconductor light emitting element group higher in the high-luminance section than in the low-luminance section. The control device is
The drive current for the semiconductor light emitting device group is duty-modulated with respect to the first direction, and the current supply time within one cycle is reduced in the low-luminance section than in the high-luminance section.
Claims 1 to 6 for increasing the current density of the semiconductor light emitting device in the low brightness portion while the current is being supplied to be larger than the current density of the semiconductor light emitting element in the high brightness portion while the current is being supplied. The vehicle lighting equipment according to any one of the above items. The vehicle lamp according to any one of claims 1 to 6, wherein the light emitting area of the semiconductor light emitting element in the semiconductor light emitting element group is the same. The vehicle lamp according to any one of claims 1 to 7 , wherein the light emitting area of the semiconductor light emitting element in the semiconductor light emitting element group is larger than that of the low brightness portion in the high brightness portion.

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