Abstract:
A lighting apparatus comprising: a reflecting surface for reflecting light, formed on a circuit board; an LED light source for emitting illumination light with a light-emitting diode, mounted on a part of said reflecting surface; and a reflector for reflecting ahead the light emitted from said LED light source, mounted on said circuit board so as to surround said LED light source and have the opened rear thereof closed by said reflecting surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Divisional of co-pending application Ser. No. 10/759,421, filed on Jan. 20, 2004, the entire contents of which are hereby incorporated by reference and for which priority is claimed under 35 U.S.C. § 120; and this application claims priority of Application Nos. 2003-011751 and 2003-011752 filed in Japan on Jan. 21, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a lighting apparatus, an electronic flash apparatus and a camera, and in particular, to the lighting apparatus, electronic flash apparatus and camera using a light-emitting diode (LED) as a light source.  
         [0004]     2. Description of the Related Art  
         [0005]     In general, an electronic flash apparatus of a camera is using a xenon tube as a light source. However, the electronic flash apparatus using the xenon tube as the light source has a drawback that strobing with a slow shutter is not possible because it can only emit instantaneous light of a few milliseconds or so. It also has a drawback that, as the xenon tube has a spectral characteristic close to daylight color, a photo of unnatural tone is made if strobing for the sake of back light correction is performed in the morning or in the evening.  
         [0006]     Thus, the electronic flash apparatus using an LED as the light source is proposed in order to resolve the drawbacks of the electronic flash apparatus using the xenon tube as the light source (refer to Japanese Patent Application Publication No. 2002-116481 for instance).  
       SUMMARY OF THE INVENTION  
       [0007]     As a light source of an electronic flash apparatus is required to emit high-intensity light, it is desirable, in the case of using an LED, to efficiently use the light emitted from the LED.  
         [0008]     However, when considering the cases of implementing a chip (type) LED, an LED lamp and so forth on a circuit board having a strobing circuit or the like implemented thereon for the reason of allowing machine implementation and reducing manufacturing cost, there is a problem that the light emitted from the LED to the rear side is irradiated on the circuit board and attenuated and is not effectively used as illumination light.  
         [0009]     As the LED is a point source, there is also a problem that its light-emitting area is smaller than that of the electronic flash apparatus of a xenon tube and can only emit the light in a narrow range.  
         [0010]     The present invention has been implemented in consideration of such circumstances, and an object thereof is to provide a lighting apparatus, an electronic flash apparatus and a camera capable of effectively using as the illumination light the light from the LED used as a light source and irradiating the light in a wide range.  
         [0011]     In order to attain the above described object, the first aspect of the present invention provides a lightning apparatus comprising a reflecting surface for reflecting the light, formed on a circuit board, an LED light source for emitting illumination light with a light-emitting diode, mounted on a part of the above described reflecting surface, and a reflector for reflecting ahead the light emitted from the above described LED light source, mounted on the above described circuit board so as to surround the above described LED light source and have the opened rear thereof closed by the above described reflecting surface.  
         [0012]     According to the invention, the light emitted from the LED light source in the rear direction is reflected ahead by the reflecting surface of the circuit board and is effectively used as the illumination light.  
         [0013]     Preferably, the above described reflecting surface is formed by gold-plating.  
         [0014]     Preferably, the above described LED light source is a surface-mounted white light-emitting chip LED and is surface-mounted on the above described reflecting surface. Machine implementation of the LED light source on the circuit board is thereby possible so as to reduce manufacturing cost.  
         [0015]     Preferably, the above described LED light source is comprised of three types of LED light sources for emitting red light, green light and blue light, and the LED light source for emitting the light in each color is radially placed. To be more specific, white light-emitting is enabled by mixing the three colors of red, green and blue, and it becomes easier to mix them by radially placing them.  
         [0016]     Preferably, an optical component for expanding and flooding ahead the light emitted from the above described LED light source is placed on the above described reflector. It is thereby possible to use the light from the above described LED light source which is strongly oriented as the illumination light for illuminating a wide range.  
         [0017]     The second aspect of the present invention provides a lightning apparatus having an LED light source for emitting the illumination light with a light-emitting diode, and the reflector for reflecting ahead the light emitted from the above described LED light source, the above described reflector placed so as to surround the rear side and side surface side of the above described LED light source, and the above described LED light source is placed clear of an internal reflecting surface of the above described reflector.  
         [0018]     According to the invention, the rear side of the LED light source is surrounded by the reflector, and the LED light source is placed clear of the internal reflecting surface of the reflector. Therefore, the light emitted to the rear side from the LED light source is reflected ahead by the reflector so that the light emitted from the LED light source will be effectively used as the illumination light.  
         [0019]     Preferably, the above described LED light source has a lead terminal, and the above described lead terminal is put through a hole provided on the above described reflector and is joined with a predetermined pad of the circuit board so as to mount the above described LED light source on the above described circuit board. To be more specific, it is possible, by using an LED lamp having the lead terminal as the LED light source, to place the LED light source clear of the internal reflecting surface of the reflector with the lead terminal as a supporting element when joining (electrically connecting) the lead terminal with the predetermined pad of the circuit board. Machine implementation also becomes possible so as to reduce manufacturing cost.  
         [0020]     The above-mentioned lighting apparatus is suitable as the electronic flash apparatus of the camera.  
         [0021]     The third aspect of the present invention provides an electronic flash apparatus comprising a light-emitting portion having an LED light source for emitting the illumination light with the light-emitting diode, and a reflector for reflecting ahead the light emitted from the LED light source, and a lens for expanding and flooding ahead the light emitted from the light-emitting portion, placed in front of the above described light-emitting portion.  
         [0022]     According to the invention, it is possible, by placing the lens for expanding ahead the light in front of the light-emitting portion, to expand and irradiate the light from the light-emitting diode emitted as a point source. Thus, it is possible to illuminate a wide range even in the case of using the light-emitting diode which is the point source and is strongly oriented.  
         [0023]     Preferably, an optical element for diffusing the light emitted from the above described LED light source is placed between the above described LED light source and the above described lens.  
         [0024]     According to the invention, it is possible to expand the light-emitting area of the light-emitting portion by diffusing the light emitted from the above described LED light source with the optical element.  
         [0025]     Preferably, the above described optical element diffuses the light emitted from the above described LED light source and also converts it into predetermined color temperature.  
         [0026]     According to the invention, it is possible to adjust the light emitted from the LED light source at the predetermined color temperature with the optical element.  
         [0027]     Preferably, the electronic flash apparatus comprises a movement device which relatively moves the above described light-emitting portion and the above described lens in an optical axis direction, and changes an irradiation angle of the light emitted from the above described lens by relatively moving the above described light-emitting portion and the above described lens in the optical axis direction with the movement device.  
         [0028]     According to the invention, it is possible to change the irradiation angle of the light emitted from the lens by relatively moving the light-emitting portion and the lens in the optical axis direction with the movement device.  
         [0029]     The electronic flash apparatus may be arranged in a camera body to provide a camera.  
         [0030]     As described above, according to the present invention, the light emitted in the rear direction from an LED light source is reflected ahead by the reflecting surface of the circuit board having the LED light source mounted thereon or by the internal reflecting surface of the reflector so as to be effectively utilized as the illumination light. It is also possible, by placing the lens for expanding the light in front of the light-emitting portion, to expand and irradiate the light from the light-emitting diode emitted as the point source. Thus, it is possible to shed the light in a wide range even in the case of using the light-emitting diode which is the point source and is strongly oriented. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a front perspective view showing an embodiment of a camera having an electronic flash apparatus according to the present invention built therein;  
         [0032]      FIG. 2  is a perspective view showing configuration of the electronic flash apparatus according to a first embodiment;  
         [0033]      FIG. 3  is a perspective view showing a mounting structure of a chip LED on a circuit board;  
         [0034]      FIG. 4  is a perspective view showing a mounting structure of a reflector on the circuit board;  
         [0035]      FIG. 5  is a longitudinal section showing configuration of the electronic flash apparatus according to the first embodiment;  
         [0036]      FIG. 6  is a perspective view showing a mounting structure of chip LEDs of three colors RGB on the circuit board;  
         [0037]      FIG. 7  is a perspective view showing a mounting structure of a LED lamp on the circuit board according to a second embodiment;  
         [0038]      FIG. 8  is a sectional view showing the electronic flash apparatus in  FIG. 7  from a side surface direction; and  
         [0039]      FIG. 9  is a longitudinal section of the electronic flash apparatus according to a third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0040]     Hereafter, preferred embodiments of a lighting apparatus, an electronic flash apparatus and a camera according to the present invention will be described by referring to the drawings.  
         [0041]      FIG. 1  is a front perspective view showing an embodiment of a camera having an electronic flash apparatus according to the present invention built therein.  
         [0042]     This camera  1  is a digital camera for converting an optical image of a subject into a digital signal by using a CCD and recording it on a recording medium. A taking lens  3 , a finder window  4 , a electronic flash apparatus  5 , a electronic flash dimmer window  6  and so on are provided at the front of a camera body  2  thereof, and a release button  7 , a power switch  8  and so on are provided on the top surface. And a finder eye piece, a liquid crystal monitor, various operation buttons and so on are provided on the rear of the camera body  2  although not shown.  
         [0043]      FIG. 2  is a perspective view showing configuration of a first embodiment of the electronic flash apparatus  5  built in the camera body  2  of the camera  1  shown in  FIG. 1 .  
         [0044]     As shown in  FIG. 1 , the electronic flash apparatus  5  is comprised of a light-emitting portion  9  comprising a chip (type) LED  10 , a reflector  12  and a diffusion plate  14  and a concave lens  16  for expanding and flooding ahead the light emitted from the light-emitting portion  9 . It is mounted on a circuit board  18  (printed board for instance).  
         [0045]     The circuit board  18  has circuit components (a strobing circuit for controlling light emission of the chip LED  10  of the electronic flash apparatus  5  for instance) mounted thereon. The circuit board  18  has a mounting land  20  to which gold plate is affixed provided thereon, and the electronic flash apparatus  5  is mounted on the mounting land  20 .  
         [0046]     The chip LED  10  which is a light source is surface-mountable, and emits white light at high intensity. The chip LED  10  has two electrode pads (not shown) provided thereto. As shown in  FIG. 3 , those electrode pads are joined with pads  24  provided on the mounting land  20  of the circuit board  18  with a conductive adhesive such as a soldering paste. Thus, the chip LED  10  is firmly fixed on the mounting land  20 , and is electrically connected to the strobing circuit mounted on the circuit board  18 . The pads  24  of the mounting land  20  are isolated from the gold plate. The method for mounting the chip LED  10  on the circuit board  18  is not limited to the above-mentioned case.  
         [0047]     The reflector  12  is formed like a rectangular tube expanding toward its end. It is mounted on the circuit board  18  so as to surround the chip LED  10  firmly fixed on the mounting land  20  so as to reflect ahead the light emitted from the chip LED  10 . As shown in  FIG. 4 , a pair of claws  26 A and  26 B is provided on the circumference of a base edge portion of the reflector  12 . The reflector  12  is fixed on the circuit board  18  by fitting the claws  26 A and  26 B in mounting holes  28 A and  28 B formed on the circuit board  18 .  
         [0048]     The diffusion plate  14  is mounted in the reflector  12  to diffuse the light emitted from the chip LED  10  and also convert it into predetermined color temperature. The diffusion plate  14  is formed in accordance with a sectional shape of the reflector  12 , and is fixed by being appressed to an internal wall of the reflector  12 . Accordingly, all the light emitted from the chip LED  10  passes through the diffusion plate  14 .  
         [0049]     The concave lens  16  is mounted at the end of the reflector  12 , and expands and floods ahead the light from the chip LED  10  emitted via the diffusion plate  14 . The concave lens  16  is formed in accordance with the shape of the end opening of the reflector  12 , and is mounted so as to block the end opening of the reflector  12 .  
         [0050]     The action of the electronic flash apparatus  5  of the present invention having the above-described configuration is as follows.  
         [0051]     As shown in  FIG. 5 , the light emitted from the LED (chip) of the chip LED  10  as the light source passes through the diffusion plate  14  first so as to be diffused and converted into predetermined color temperature. And the light source having passed through the diffusion plate  14  passes through the concave lens  16  so as to be radially expanded and flooded ahead. Thus, it is possible to irradiate in a wide range the light from the LED emitted as a point source and strongly oriented.  
         [0052]     According to the electronic flash apparatus  5  of the present invention, the light emitted from the chip LED  10  in the side surface direction is reflected ahead by the reflector  12 , and the light emitted from the chip LED  10  in the rear direction is reflected ahead by the gold plate affixed on the mounting land  20 . Thus, it is possible to effectively utilize the light emitted from the chip LED  10  in the side surface direction and the rear direction as illumination light ahead.  
         [0053]     It is also possible, by mounting the chip LED  10  and so on on the circuit board  18 , to cut down on the number of components and reduce manufacturing cost.  
         [0054]     According to this embodiment, one white light-emitting chip LED  10  is used as the light source of the electronic flash apparatus  5 . It is also possible, however, to mount not only one but a plurality of white light-emitting chip LEDs on the mounting land  20  of the circuit board  18  and use them as the light sources.  
         [0055]     It is also possible, instead of using the white light-emitting chip LED  10  as the light source of the electronic flash apparatus  5 , to use the chip LEDs in different luminescent colors such as those for emitting red light, green light and blue light so as to radiate white illumination light by mixing the light in these colors. In this case, it is desirable, as shown in  FIG. 6 , to radially place chips  10 R,  10 G and  10 B for emitting the red light, green light and blue light on the mounting land  20  of the circuit board  18 . To be more specific, three pairs of pads  24 R,  24 G and  24 B are radially provided on the mounting land  20  of the circuit board  18  as with the pair of pads  24  shown in  FIG. 3 , and the chip  10 R for emitting the red light, the chip  10 G for emitting the green light and the chip  10 B for emitting the blue light are affixed to the pairs of pads  24 R,  24 G and  24 B respectively. Thus, it is possible to efficiently mix the light emitted from the chips  10 R,  10 G and  10 B.  
         [0056]     The case of radiating the white illumination light was described in this embodiment. It is also possible, however, to radiate the illumination light in another color, and in that case, the chip LED of the luminescent color in accordance with that color may be used.  
         [0057]     Furthermore, according to this embodiment, the gold plate is affixed on the surface of the mounting land  20  so as to reflect ahead the light emitted from the chip LED  10  in the rear direction. It is also possible, however, to form the surface of the mounting land  20  with a material other than the gold plate if it has the effect of reflecting the light.  
         [0058]     According to this embodiment, the surface-mounted chip LED  10  is used as the light source of the electronic flash apparatus  5 . However, the form of the LED to be used as the light source is not limited thereto, and it is also possible to use a LED lamp  10 A having a lead terminal provided thereon instead of the chip LED  10 .  
         [0059]     Next, a description will be given as to configuration of a second embodiment of the electronic flash apparatus to which the present invention is applied to. The circuit board  18  in  FIG. 7  showing this embodiment has the circuit components such as the strobing circuit mounted thereon as with the first embodiment, and the electronic flash apparatus  5  is mounted in a portion thereof.  
         [0060]     In  FIG. 7 , optical components such as the diffusion plate and concave lens shown in  FIG. 2  are omitted. The electronic flash apparatus  5  has two lead terminals provided thereto, and is comprised of the LED lamp  10 A for emitting the white light at high intensity and a reflector  12 A opening only at the front. The reflector  12 A can be mounted on the circuit board  18  by fitting the claws  26 A and  26 B (one of them is not shown) provided on the side surface thereof in mounting holes  28 A and  28 B on the circuit board  18  as with the first embodiment.  
         [0061]     As shown in a side sectional view in  FIG. 8 , holes  54  and  56  penetrating two lead terminals  52  of the LED lamp  10 A respectively are formed on the rear (bottom face) of the circuit board  18  and the reflector  12 A. The two lead terminals  52  of the LED lamp  10 A are inserted into the holes  54  and  56  and soldered on the rear of the circuit board  18  so that the LED lamp  10 A is mounted on the circuit board  18  and is electrically connected to the strobing circuit.  
         [0062]     As shown in  FIG. 8 , the LED lamp  10 A is placed so that its bottom is clear of the bottom face of the reflector  12 A. Thus, not only the light emitted from the LED lamp  10 A in the side surface direction but also the light emitted in the rear direction is reflected ahead by an internal reflecting surface of the reflector  12 A, and is effectively used as the illumination light.  
         [0063]     It is also possible to change the configuration of the second embodiment as with the first embodiment. For instance, a plurality of LED lamps  10 A may be used as the light source instead of one LED lamp  10 A. It is also possible to radiate the white illumination light with the LED lamps for emitting the red light, green light and blue light. The illumination light may be in a color other than white, and in that case, the LED lamp of the luminescent color in accordance with that color should be used.  
         [0064]     In the case of using the LED lamp as the light source in the first embodiment, it is possible to place the LED lamp so that its bottom is clear of the mounting land  20  as with the second embodiment.  
         [0065]      FIG. 9  is a longitudinal section showing configuration of a third embodiment of the electronic flash apparatus according to the present invention.  
         [0066]     As shown in  FIG. 9 , a electronic flash apparatus  30  according to this embodiment is equivalent to the electronic flash apparatus  5  in the above-mentioned first embodiment holding the concave lens  16  placed in front of the light source movable back and forth along an optical axis, which renders an irradiation angle of the light irradiated from the electronic flash apparatus variable. The same components as those of the electronic flash apparatus  5  in the above-mentioned embodiment will be given the same symbols, and a description thereof will be omitted.  
         [0067]     As shown in  FIG. 9 , the concave lens  16  held by a lens frame  32  is placed in front of the light-emitting portion  9  comprised of the chip LED  10 , reflector  12  and diffusion plate  14 , and a transparent cover glass  34  is placed in front of it. The cover glass  34  is fitted into an exterior  2 A of the camera body.  
         [0068]     The lens frame  32  for holding the concave lens  16  has a guide portion  36  and a nut portion  38  integrally formed on its circumference.  
         [0069]     The guide portion  36  has a guide hole  36 A formed along an optical axis L of the concave lens  16 , and a guide bar  40  placed along the optical axis L is inserted into the guide hole  36 A. The guide bar  40  is fixed by an unshown frame placed in the camera body. And the guide portion  36  slides along the guide bar  40  so that the concave lens  16  moves back and forth along the optical axis L in front of the light-emitting portion  9 .  
         [0070]     The nut portion  38  has a screw hole  38 A formed along the optical axis L of the concave lens  16 , and a screw bar  42  placed along the optical axis L is screwed into the screw hole  38 A. The screw bar  42  is linked to an output axis of a motor  44  placed in the camera body, and is rotated by driving the motor  44 . And the nut portion  38  moves along the screw bar  42  as the screw bar  42  is rotated so that the concave lens  16  thereby moves back and forth along the optical axis L.  
         [0071]     The motor  44  for rotatively driving the screw bar  42  has its drive controlled by a control portion (CPU) for centrally controlling the digital camera  1 , and is driven in conjunction with zooming of the taking lens  3 . To be more specific, the drive is controlled so that the irradiation angle of the light irradiated via the concave lens  16  changes according to a field angle of the taking lens  3 .  
         [0072]     According to the electronic flash apparatus  30  of this embodiment constituted as above, it is possible, by moving the concave lens  16  placed in front of the light-emitting portion  9  back and forth along the optical axis L, to change the irradiation angle of the light irradiated via the concave lens  16  according to the field angle of the taking lens  3 . Thus, it is possible to effectively utilize the light irradiated from the chip LED  10  as the light source.  
         [0073]     According to this embodiment, the light-emitting portion  9  is fixed and the concave lens  16  is moved back and forth to the light-emitting portion  9  which is fixed. However, it may be inverse. To be more specific, it is also possible to fix the concave lens  16  and move the light-emitting portion  9  back and forth to the concave lens  16  along the optical axis L of the concave lens  16 .  
         [0074]     The above-mentioned embodiment was described by taking an example in which the electronic flash apparatus according to the present invention is built into the digital camera. It is also possible, however, to use it for a silver salt camera using a film or apply it to a lighting apparatus for other uses.  
         [0075]     This embodiment was also described by taking an example in which the electronic flash apparatus according to the present invention is built into the camera body. It is also possible, however, to independently constitute it (a so-called external electronic flash apparatus).