JP2008147485A - Semiconductor light-emitting-device and light distribution control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting-device whose light distribution can be electrically controlled and a light distribution control method. <P>SOLUTION: The semiconductor light-emitting-device includes a package having a recess, a plurality of semiconductor light-emitting-devices located in the recess, a first combination composed of any semiconductor light-emitting-elements which are two or more among a plurality of the semiconductor light-emitting-elements, a second combination composed of the other semiconductor light-emitting-elements which are two or more among a plurality of the semiconductor light-emitting-elements, and a plurality of electrodes which can independently supply an electric current for them respectively. Each driving condition of the first and second combinations is independently controlled, thereby, the light distribution is made variable. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device and a light distribution distribution control method using the same.

  An imaging device including a digital camera and a video camera is provided with an illumination device having a flash function such as a strobe. As such an illuminating device, a xenon tube or the like has been used so far. In recent years, technological progress of nitride-based semiconductor light-emitting devices has been remarkable. As a result, it is expected that the white semiconductor light-emitting device will be replaced with a xenon tube.

  In addition, photographing apparatuses are being installed in about 90% of domestic mobile phones. However, its photographing function is insufficient as compared with a digital camera. In particular, there is much room for improvement in the flash function in dark places and in backlight photography. One reason is that it is difficult to use a xenon tube in a portable electronic device including a cellular phone due to a limited battery capacity. That is, in the case of a cellular phone, it is desirable to use a white semiconductor light emitting device that consumes less power and can be driven at a low voltage, instead of a xenon tube.

  However, the light intensity of the white semiconductor light emitting device is still small compared to the xenon tube. As a result, for example, even if necessary illuminance is obtained in the vicinity of the center of the photographing range, there is a problem that dark place contrast cannot be secured because necessary illuminance cannot be obtained in the vicinity of the periphery of the photographing range.

There is a technology disclosure example in which the light distribution from the xenon tube and the reflecting plate adjacent to the xenon tube is controlled according to the subject position by changing the rotation angle of the light shielding plate (Patent Document 1).
JP 2003-140234 A

  Provided are a semiconductor light emitting device and a light distribution distribution control method capable of electrically controlling a light distribution.

  According to one aspect of the present invention, the package includes a package having a recess, a plurality of semiconductor light emitting elements provided in the recess, and any two or more semiconductor light emitting elements among the plurality of semiconductor light emitting elements. A plurality of electrodes capable of supplying power independently to each of the first combination and the second combination of any two or more other semiconductor light emitting elements among the plurality of semiconductor light emitting elements. The semiconductor light emitting device is characterized in that the light distribution is variable by independently controlling the driving conditions of the first and second combinations.

  According to another aspect of the present invention, there is provided an imaging apparatus comprising the semiconductor light emitting device described above, wherein the light distribution distribution to the subject is controlled by supplying power independently to the plurality of electrodes. Is done.

  Provided are a semiconductor light emitting device and a light distribution distribution control method capable of electrically controlling the light distribution.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A and 1B show a semiconductor light emitting device according to a first specific example of the present invention, in which FIG. 1A is a schematic plan view and FIG. 1B is a partially cut schematic sectional view. In the semiconductor light emitting device of this specific example, the plurality of semiconductor light emitting elements 20a to 20d are arranged in the recess 46 of the package 40 made of ceramic or the like. Four bottom metallized portions 41 are provided on the bottom surface of the recess 46. These bottom metallized portions 41 penetrate through the package 40 and are connected to the cathode electrodes 42 formed on the side surfaces thereof. One electrode of the semiconductor light emitting device 20 is connected to the bottom metallized portion 41 and the bonding wire 21. Further, the other electrode of the semiconductor light emitting element 20 is connected to, for example, an anode electrode 44 provided on the back surface of the package through a through hole provided in the package 40.

  Accordingly, by independently supplying power to each of the four cathode electrodes 42 provided on the side surface of the package 40, the operations of the four semiconductor light emitting elements 20a to 20d can be controlled independently. Here, it is not necessary to control all of the plurality of semiconductor light emitting elements 20 independently. For example, any two or more semiconductor light emitting elements selected from the plurality of semiconductor light emitting elements 20 are used as a first combination, and any other two or more selected from the plurality of semiconductor light emitting elements 20 are combined. The semiconductor light emitting element is a second combination, and power is supplied to the electrodes corresponding to the combination number or more independently for each of these two combinations. As a result, driving conditions can be set independently for each combination.

  For example, among the four semiconductor light emitting elements 20a to 20d shown in FIG. 1A, the upper two semiconductor light emitting elements 20a and 20c are combined into one combination, and the lower two semiconductor light emitting elements 20b and 20d are combined. The second combination can be controlled independently. In this way, the alignment characteristics in the vertical direction can be controlled.

On the other hand, for example, among the four semiconductor light emitting elements 20a to 20d shown in FIG. 1A, the upper left semiconductor light emitting element 20a and the lower right semiconductor light emitting element 20d are combined into one combination, and the lower left semiconductor light emitting element 20b is combined. And the upper right semiconductor light emitting element 20c as a second combination, these two combinations can be controlled independently. In this case, the alignment characteristics in the oblique direction can be controlled.
In any of these cases, the semiconductor light emitting elements 20 in the same combination may be connected by an electrode inside the package 40 or may be connected by a circuit outside the package 40.

  In this specific example, four semiconductor light emitting elements 20 (20a, 20b, 20c, 20d) are arranged, four bottom metallized portions 41 are arranged in a cross shape, and the cathode electrode 42 is the number 4 of the package 40. It arrange | positions so that a corner | angular part side surface may make a curved surface, However, This invention is not limited to these structures and arrangement | positioning. A modification will be described later.

  2A and 2B show a semiconductor light emitting element 20 constituting this example, where FIG. 2A is a schematic plan view and FIG. 2B is a schematic cross-sectional view. For example, the light emitting layer 24 is provided on the substrate 22, and the n-type electrode 26 is provided on the light emitting layer 24. On the other hand, a p-type electrode 28 is provided on the back surface of the substrate 22. The semiconductor material may be InGaAlP, AlGaAs, InGaAlN, or the like.

  For example, by using silicon carbide (SiC) as the substrate 22 and growing a semiconductor stacked body including a light emitting layer with a nitride material such as an InGaAlN semiconductor, a semiconductor light emitting device having an emission wavelength in the range of 380 to 600 nm is obtained. . In this case, by using a blue semiconductor light-emitting element having a wavelength of about 405 nm and mixing the yellow phosphor into the sealing resin and filling the recess 46, white light is mixed by mixing yellow light and blue light obtained by wavelength conversion. Is obtained. This white light is preferable as flash illumination light. A semiconductor light-emitting device is preferable as a lighting device mounted on a portable electronic device because it is driven at a low voltage of 3 to 5 V, has a long operating life, and can be downsized. In this case, if SiC, sapphire, GaP, or the like, which is a transparent material in this wavelength band, is used as the substrate 22, the light extraction efficiency can be increased.

Further, on two adjacent side surfaces of the semiconductor light emitting element 20, for example, a SiO ₂ film (thickness 0.2 μm) formed by plasma CVD and a silver film (thickness 1 μm) formed by vacuum deposition are stacked in this order. A reflective film 30 is configured. Although the emitted light from the light emitting layer 24 is radiated | emitted from each side surface, light is not radiated | emitted from the side surface in which the reflecting film 30 was formed. The reflectance of the reflective film 30 is preferably 50% or more.

  As illustrated in FIG. 1A, two adjacent side surfaces provided with the reflective film 30 of the semiconductor light emitting element 20 are arranged to face each other. In addition, in order to make distinction with another side surface easy, the reflecting film 30 was represented with the broken line. Of the radiated light from the light emitting layer of the semiconductor light emitting element 20, most of the light reflected by the reflective film 30 is radiated to the outside via the semiconductor light emitting element 20. In FIG. 1, the reflective film 30 is provided on the inner side surface where the semiconductor light emitting elements 20 are adjacent to each other, but the present invention is not limited to this. In addition to this, for example, the reflective film 30 may be provided on one or both of the two side surfaces opposed to the two side surfaces provided with the reflective film 30 in the semiconductor light emitting element 20 shown in FIG.

Next, directivity characteristics in the semiconductor light emitting device 50 according to the first specific example will be described.
3A and 3B are diagrams for explaining the directional characteristics of the semiconductor light emitting elements 20a and 20b that emit light. FIG. 3A shows the path of the emitted light in the semiconductor light emitting device, and FIG. 3B shows the directional characteristics. . Since the reflective film 30 is formed on the side surface of the semiconductor light emitting element 20 adjacent to the bottom metallized portion 41, light is hardly emitted through the reflective film 30. As shown in FIG. 3A, the light reflected by the reflective film 30 travels in the outer peripheral direction and upward. Of these, most of the emitted light toward the outer peripheral portion corresponds to the side wall of the recess 46 of the package 40. The light reflected by the side wall proceeds as shown in FIG. 3A, but there is little radiated light due to the reflective film 30 in the vicinity of the vertical center axis AA of the package 40.

  The directivity characteristic of the radiated light in the cross section of Fig.3 (a) is the same figure (b). The relative value of the radiation intensity is expressed in the radial direction with respect to the angle from the AA axis. In the vicinity of the alternate long and short dash line AA representing the vertical center axis of the semiconductor light emitting device 50, the radiation intensity decreases. In this figure, the angle at which the emitted light is maximum is about 20 degrees.

  Next, the fact that the light distribution can be controlled by the semiconductor light emitting device 50 according to the present specific example will be described using a camera as an example.

  FIG. 4 is a diagram for explaining a camera in which the semiconductor light emitting device 50 according to the first specific example is a flash. FIG. 4A is a diagram schematically showing the configuration, and FIG. Is the light distribution characteristic when the flash is irradiated in the vicinity of the center of the photographing range, (c) is the light distribution characteristic when the flash is irradiated on the left side, and (d) is the light distribution characteristic when the flash is irradiated on the right side. . When the main surface of the semiconductor light emitting device 50 is vertical as shown in FIG. 4A and the semiconductor light emitting elements 20a and 20b are parallel to the vertical axis, the directivity characteristics in the horizontal plane are This is exemplified in 3 (b).

  In general, since all the semiconductor elements 20 emit light at the same time, light having an isotropic radiation pattern is emitted within the imaging range 60 regardless of the position of the subject 14. As a result, as shown in FIG. 4A, the illuminance is maximized near the center of the imaging range 60, and the light distribution is almost symmetrical. However, the subject 14 on the right side to be irradiated with the flash cannot be sufficiently irradiated.

  On the other hand, as illustrated in FIG. 3, the semiconductor light emitting device 50 that emits light from the semiconductor light emitting elements 20 a and 20 b can have a light distribution with the maximum illuminance on the right side as shown in FIG. As a result, the right subject 14 can be efficiently irradiated. FIG. 4C shows the light distribution in the case where it is desired to irradiate a flash on the subject on the left side, which is made possible by causing the semiconductor light emitting elements 20c and 20d in FIG. 1A to emit light.

  It is also possible to control the light distribution in the vertical direction. That is, for example, the upper subject 14 can be irradiated with flash by causing the semiconductor light emitting elements 20a and 20d to emit light, and the lower subject 14 can be irradiated with flash by causing the semiconductor light emitting elements 20b and 20c to emit light. Can do. Note that the driving state of the semiconductor light emitting element 20 can be changed not only on and off, but also in a stepwise manner.

  Although the above is a case where the two semiconductor light emitting elements 20 emit light, the driving state is not limited to this. For example, the upper right side can be maximized by the semiconductor light emitting element 20a, the lower right side by 20b, the lower left side by 20c, and the upper left side by 20d. Furthermore, for example, when three of the semiconductor light emitting elements 20a, 20b, and 20c are made to emit light, the range excluding the upper left side can be illuminated brightly. The same applies to the case where the other three are made to emit light.

5A and 5B show a first modification of the first specific example, in which FIG. 5A is a schematic plan view, and FIG. 5B is a schematic front view. In addition, the same number is attached | subjected to the component similar to FIG. 1, and description is abbreviate | omitted.
FIG. 6 shows the semiconductor light emitting element 20 arranged in the first modification, wherein FIG. 6A is a schematic plan view and FIG. 6B is a schematic cross-sectional view. Also in FIG. 6, the same components as those in FIG.
First, as illustrated in FIG. 6, the reflective film 30 is formed on the three side surfaces of the semiconductor light emitting element 20. In the semiconductor light emitting element 20, one side surface on which the reflective film 30 is not formed is disposed so as to face the outside of the package 50. In FIG. 5A, the reflective film 30 is indicated by a broken line so that it can be easily distinguished from other side surfaces. The bottom metallized portion 41 is disposed at each position adjacent to the semiconductor light emitting element 20, and the semiconductor light emitting element 20 is also connected to one electrode by a bonding wire 21.

In the first modification, the semiconductor light emitting element 20a can irradiate the right side, 20b the lower side, 20c the left side, and 20d the upper side.
The semiconductor light emitting elements 20a and 20d can maximize the upper right side, 20a and 20b the lower right side, 20b and 20c the lower left side, and 20c and 20d the upper left side. When three of 20a, 20d, and 20c are made to emit light, bright illumination can be performed except for the lower side. The same applies to the other three combinations. In addition, when the four are simultaneously emitted, a substantially isotropic light distribution can be obtained within the imaging range 60. In this specific example, since the reflective films 30 are provided on the three side surfaces, the directivity can be made narrower than the first specific example of FIG.
In contrast to the example illustrated in FIG. 5, the reflective film 30 may be provided only on one outer side surface where the reflective film 30 is not formed in each semiconductor light emitting element 20.

  7A and 7B show a second modification of the first specific example, in which FIG. 7A is a schematic plan view, FIG. 7B is a schematic plan view of a semiconductor light emitting element, and FIG. It is a schematic cross section. In this figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals and description thereof is omitted. In this case, the reflective film 30 is formed on only one side surface of the semiconductor light emitting element 20, and the reflective film 30 is disposed so as to face the vicinity of the center portion of the package 50.

  The semiconductor light emitting element 20a can irradiate the right side of the imaging range 60, the lower side by 20b, the left side by 20c, and the upper side by 20d. Also, the lower right side can be irradiated by the semiconductor light emitting elements 20a and 20b. Furthermore, the area | region except the upper side can be irradiated by three of 20a, 20b, and 20c. The same applies to the other three combinations. In this specific example, since the reflective film 30 is provided only on one surface facing the center of the package 40, the directivity can be made wider than that of the first specific example of FIG.

  8A and 8B show a third modification of the first specific example, in which FIG. 8A is a schematic plan view, FIG. 8B is its directivity, and FIG. 8C is a light distribution. In addition, the same number is attached | subjected to the component similar to FIG. 1, and description is abbreviate | omitted. The semiconductor light emitting device 20 is arranged so as to surround one (20e) having the same center as the vertical center axis and having no reflection film formed and having radiation emitted mainly toward the center of the imaging range 60, 4 (20a, 20b, 20c, 20d) provided with the reflective film 30 on the three side surfaces illustrated in FIG. In this figure, the radiated light from the side surface on which the reflective film 30 is not formed irradiates the oblique upper side and the oblique lower side of the imaging range 60. That is, the semiconductor light emitting element 20a emits the upper right side, 20b the lower right side, 20c the lower left side, and 20d the upper left side.

  In the third modification, the degree of freedom in controlling the light distribution is increased. For example, FIG. 8B shows directivity characteristics when the semiconductor light emitting elements 20a, 20b, and 20e emit light, and the light intensity can be set to a substantially constant value in a wide range from 0 degrees to 30 degrees. The distribution A in FIG. 8C is when the semiconductor light emitting elements 20a, 20b, and 20e are emitting light, the distribution B is when the semiconductor light emitting elements 20a and 20b are emitting light, and the distribution C is that the semiconductor light emitting element 20e emits light. In each case, the light distribution is shown. Although the right side can be illuminated by 20a and 20b (distribution B), the illuminance at the center is lower than that of distribution A because 20e is not emitted. In addition, when the four light sources 20a, 20b, 20c, and 20e are caused to emit light, the region other than the upper left side can be irradiated.

As described above, by changing the combination of the semiconductor light emitting elements 20 (20a, 20b, 20c, 20d, and 20e) that emit light, it is easy to control the light distribution. In the first specific example and the first to third specific examples associated therewith, the overall light distribution is controlled by forming the reflective film 30 on the side surface of the semiconductor light emitting device.
In the above specific example and the accompanying modification, the reflective film 30 is provided on at least the side surface closest to the center among the side surfaces of the semiconductor light emitting element 20 arranged so as to surround the center of the recess 46. In the first specific example (FIG. 1), on the two side surfaces, in the first modified example (FIG. 5), on the three side surfaces, in the second modified example (FIG. 7), on one side surface, in the third modified example (FIG. 8), the center. Except for the arranged semiconductor light emitting elements, they are provided on three side surfaces. Further, the reflective film 30 is not formed on at least one surface facing the side wall of the recess 46. Furthermore, the side surface of the semiconductor light emitting element 20 provided with the reflective film 30 may be inclined instead of the vertical surface.

The present invention is not limited to these. Even without a reflective film, the distribution of light distribution can be controlled by changing the driving conditions of the semiconductor light emitting element 20 respectively. 9A and 9B show a semiconductor light emitting device 70 according to a second specific example of the present invention that controls the light distribution without forming a reflective film. FIG. 9A is a schematic perspective view, and FIG. 9B is a schematic diagram. The top view and the same figure (c) are typical sectional views.
FIG. 10 is a view for explaining a structure for mounting the semiconductor light emitting element 20 on the submount substrate. FIG. 10A is a schematic plan view, a schematic front view, and a side view, and FIG. It is a model perspective view. In the first specific example and the first to third modifications associated therewith, the back surface of the semiconductor light emitting element 20 is mounted on the bottom surface of the recess 46 of the package 40. On the other hand, in the second specific example, the semiconductor light emitting element 20 is mounted on the cathode electrode (mount surface) 73 of the submount substrate (support member) 72 made of ceramic or the like. An anode electrode 74 is provided on the submount substrate 72 and is connected to one electrode of the semiconductor light emitting element 20 by wire bonding.

  Further, the main surface of the semiconductor light emitting element 20 and the bottom surface of the concave portion 78 of the package 70 made of ceramic or the like are arranged to be approximately 90 degrees. The light emitted in the substantially vertical direction of the main surface of the semiconductor light emitting element 20 is reflected by the inclined side surface of the recess 78 of the package 70 and travels upward. In the second specific example, a plurality of submount substrates 72 are arranged so as to face the side surface of the recess 78 of the package 70, and the light distribution is controlled by changing the driving conditions. For example, the semiconductor light emitting element 20a can irradiate the right side, 20b the lower side, 20c the left side, and 20d the upper side. The lower right side can be irradiated by 20a and 20b, the lower left side by 20b and 20c, the upper left side by 20c and 20d, and the upper right side by 20d and 20a. Furthermore, if three of 20a, 20b, and 20c are made to emit light, the area | region except an upper side can be irradiated. As a result, the same effect as the first specific example can be obtained. In this case, the step of forming the reflective film 30 on the side surface of the semiconductor light emitting element 20 can be omitted.

  Next, a light distribution control method using the semiconductor light emitting device according to the specific example will be described. FIGS. 11A and 11B are schematic views illustrating a photographing apparatus including the semiconductor light emitting device according to the embodiment of the present invention. FIG. 11A shows the liquid crystal screen and FIG. 11B shows the light distribution. FIG. 12 is a flowchart for lighting the semiconductor light emitting element 20 by selecting the driving condition of the semiconductor light emitting element 20 according to the position of the subject 85. First, a scene mode is selected in a photographing apparatus such as the digital camera 80 (S200). Scene modes include portrait, sport, distant view, night view, night view portrait snow, candle light, etc., which can be selected by the photographer.

  Subsequently, image recognition is performed by a CCD or CMOS sensor (S202). When the position information of the subject 85 obtained by the image recognition is input to the semiconductor light emitting device control circuit, either automatic or manual by the photographer is selected. In the case of automatic input, the position information for image recognition is automatically input to the semiconductor light emitting device control circuit (206), and the driving conditions for the semiconductor light emitting element 20 are determined (S208). On the other hand, when the photographer determines the irradiation direction, the information is input by the photographer to the semiconductor light emitting device control circuit (S207), and the driving condition of the semiconductor light emitting element 20 is determined (S208). Under this driving condition, the semiconductor light emitting element is turned on (S210). As a result, since the flash can be irradiated so that the selected subject 85 has a light distribution with the maximum illuminance, a limited battery capacity can be used efficiently. Further, by using the semiconductor light emitting device, it is possible to reduce the size of the camera and extend the life of the lighting device. Furthermore, since the charge up time after lighting is unnecessary, continuous lighting is possible.

  The photographing device may be a camera that records a still image on a photosensitive film, and includes a video camera that records a moving image. Furthermore, it includes any device that can be mounted on a mobile phone, a PDA (Personal Data Assistant) or other various electronic devices and can record still images or moving images.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to these specific examples and modifications accompanying them. For example, even if a person skilled in the art makes various design changes with respect to a semiconductor element, a reflective film, a package, an image recognition unit, etc. constituting a semiconductor light emitting device, it is within the scope of the present invention without departing from the gist of the present invention. Is included.

In the present specification, the term “nitride-based material” refers to a composition ratio x and a chemical formula In _x Al _y Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, x + y ≦ 1). Semiconductors of all compositions in which y is changed within the respective ranges are included. Furthermore, in the above chemical formula, any of those containing boron (B), those containing further a group V element other than N (nitrogen), or various dopants added for controlling the conductivity type, etc. What is included is also included in “nitride-based material”.

The schematic diagram showing the semiconductor light-emitting device concerning the 1st specific example of this invention. The schematic diagram of the semiconductor light-emitting device which comprises a 1st specific example. The figure explaining the directional characteristic in the 1st specific example. The figure explaining the light distribution in the 1st specific example. The schematic diagram of the 1st modification of a 1st specific example. The schematic diagram of the semiconductor light-emitting device which comprises the 1st modification. The schematic diagram of the 2nd modification of a 1st specific example. The schematic diagram of the 3rd modification of a 1st specific example. The schematic diagram of the semiconductor light-emitting device concerning the 2nd specific example of this invention. The schematic diagram of the submount board | substrate which comprises a 2nd specific example. FIG. 4 is a diagram for explaining a method for controlling the light distribution of the digital camera according to the embodiment. The flowchart of the light distribution distribution control method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Semiconductor light-emitting element, 14 ... Subject, 30 ... Reflective film, 40 ... Package, 46 ... Recessed part, 50 ... Semiconductor light-emitting device, 60 ... Shooting range, 80. ..Digital camera, 85 ... Subject

Claims (5)

A package having a recess;
A plurality of semiconductor light emitting elements provided in the recess;
A first combination comprising any two or more semiconductor light emitting elements of the plurality of semiconductor light emitting elements and a second combination comprising any other two or more semiconductor light emitting elements of the plurality of semiconductor light emitting elements. A plurality of electrodes capable of supplying power independently to each other, and
With
A semiconductor light emitting device characterized in that the light distribution is variable by independently controlling the driving conditions of the first and second combinations. A reflective film having a higher reflectance than the interface with air is provided on the side surface of the semiconductor light emitting element, and reflects at least part of the emitted light from the light emitting layer of the semiconductor light emitting element toward the side wall of the recess. ,
2. The semiconductor light emitting device according to claim 1, wherein the emitted light directed toward the side wall is emitted to the outside after being reflected by the side wall. A support member provided in the recess and having a mounting surface substantially perpendicular to the bottom surface of the recess;
The semiconductor light-emitting device according to claim 1, wherein the semiconductor light-emitting element is mounted on the mount surface.   3. The semiconductor light emitting device according to claim 1, wherein the reflective film is provided on at least a side surface closest to the center among the side surfaces of the semiconductor light emitting element disposed so as to surround the center of the concave portion. apparatus. Detect the position of the subject within the shooting range,
5. The light distribution distribution control method according to claim 1, wherein the semiconductor light emitting device according to claim 1 is driven so that the illuminance becomes maximum in the vicinity of the position.

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