JP2005091582A - Illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illuminating device which is equipped with a semiconductor light emitting element and supplies illuminating light having no luminance irregularity and safe to human eyes. <P>SOLUTION: A light emitting unit 2 is constituted of a blue LED and a diffusing plate 4. The aspect ratios of the incident surface and the emitting surface of the diffusing plate 4 are made the same as the aspect ratio of the imaging area PA of a camera 6. By incorporating YAG-based fluorescent material into the diffusing plate 4, the diffusing plate 4 is constituted to diffuse and emit white light when blue light is made incident. The diffusing plate 4 is arranged at the focal position of a light projection optical system 5 between the blue LED and the light projection optical system 5. The focal distance (f) of the light projection optical system 5 and the size of the incident surface and the emitting surface of the diffusing plate 4 are determined so that the radiation angle of the illuminating light emitted from the light projection optical system 5 may coincide with the angle of view of the photographing optical system of the camera 6. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lighting device using a semiconductor light emitting element.

In recent years, high-brightness LEDs, white LEDs, and the like have been developed in the field of semiconductor light-emitting devices, and their application range has expanded. For example, there is a camera flash device that uses an illumination device including a white LED instead of a conventionally used xenon discharge tube. This is because problems such as a xenon discharge tube that requires a capacitor for driving, a space in the camera being narrowed, and a danger due to high voltage flow can be eliminated by using a white LED. The light emitted from the white LED is irradiated to the subject via the light projecting optical system (for example, Patent Document 1).
JP 2002-148686 A

  However, leads and wires are disposed around the LED chip, and members that emit light (chips) and members that do not emit light (leads and wires) are mixed. Therefore, when the light emitted from the LED is emitted through the light projecting optical system, there is a problem that an image of the chip and its surrounding shadow is also projected on the subject side, resulting in uneven illumination brightness.

  Further, the LED chip is extremely small, and the illumination device composed of the white LED as described above is a small point light source as a light emitting source. When such a point light source emits high-luminance white light, when the subject is a human, the emitted light forms an image in the eye, causing damage to the retina of the eye.

  An object of the present invention is to solve the above problems, and to provide illumination light that has no luminance unevenness and is safe for human eyes in an illumination device including a semiconductor light emitting element as a light source.

  An illumination device according to the present invention is interposed between a semiconductor light emitting element, a light projecting optical system for irradiating a subject with light emitted from the semiconductor light emitting element, and the semiconductor light emitting element and the light projecting optical system. And an illuminating device comprising a diffusing means for diffusing the emitted light of the semiconductor light emitting element and guiding it to the light projecting optical system, the diffusing means being arranged at the focal position of the light projecting optical system, The projection optical system has a surface similar to the imaging area of the imaging means used with the illumination device, and the emission angle of the emitted light emitted from the projection optical system matches the angle of view of the imaging optical system of the imaging means The focal length and the size of the entrance surface and exit surface of the diffusing means are defined.

  According to the present invention, the radiation angle of the light emitted from the light projecting optical system and applied to the subject is matched with the field angle of the photographing optical system of the photographing means. Therefore, the light emitted from the semiconductor light emitting element can be efficiently irradiated onto the subject as illumination light.

  FIG. 1 is a diagram schematically showing a relative positional relationship between an illumination device to which the first embodiment of the present invention is applied and a subject. The illumination device 1 includes a light emitting unit 2 and a light projecting optical system 5. The light emitting unit 2 includes a blue LED 3 that emits blue light and a diffusion plate 4. The diffuser plate 4 is a flat plate-like optical element, and its entrance surface 4a and exit surface 4b have a rectangular shape as shown in FIG. 1, and the aspect ratio thereof is equivalent to that of one camera frame used with the illumination device. The ratio of the long side: short side is 3: 2. In other words, the entrance surface 4a and the exit surface 4b of the diffusing plate 4 are similar to the imaging region of the camera. The diffusion plate 4 contains a YAG (Yttrium Aluminum Garnet) fluorescent material. When the blue light emitted from the blue LED 3 enters from the incident surface 4a, the blue light is converted into white light by the fluorescent material, diffused, and emitted from the emission surface 4b. That is, the diffusion plate 4 also functions as a secondary light emitter. In FIG. 1, only one blue LED 3 is shown, but the present invention is not limited to this, and a plurality of blue LEDs 3 may be provided.

  White light diffused and emitted from the exit surface 4 b of the diffusion plate 4 is guided to the subject as illumination light through the light projecting optical system 5. FIG. 2 shows an optical path diagram until the light emitted from the light emitting unit 2 reaches the subject OB. In FIG. 2, the blue LED 3 described above is supported by a support member 3a. In FIG. 2, a dotted line PA indicates an imaging region of the camera 6 that is used together with the illumination device 1. As described above, the diffusing plate 4 has a similar shape to the imaging area PA. The diffusing plate 4 is disposed at the focal position of the light projecting optical system 5. That is, the distance between the diffusing plate 4 and the light projecting optical system 5 is made to coincide with the focal length f of the light projecting optical system 5.

  In the first embodiment, an image of the photographing optical system in which the radiation angle θ of the emitted light of the light projecting optical system 5 is determined by the focal length of the photographing optical system (not shown) of the camera 6 and the diagonal length of the photographing film. The size of the diffusing plate 4 and the focal length f of the light projecting optical system 5 are determined so as to coincide with the corners.

  Light emitted from the blue LED 3 is diffused by the diffusion plate 4 and guided to the light projecting optical system 5. Therefore, the image of the member around the chip of the blue LED 3 is not projected on the subject as it is, and the luminance of the illumination light irradiated on the subject OB does not vary. Further, when the blue LED 3 is driven at a high luminance to increase the amount of illumination light, it is possible to avoid adversely affecting the retina even if the subject is a person.

  The diffusing plate 4 is disposed at the focal position of the light projecting optical system 5. Accordingly, light incident from one point of the diffusion plate 4 is converted into parallel light and guided to the subject OB. Further, the aspect ratio of the diffusing plate 4 is matched with the aspect ratio of the film of the camera 6. With the above configuration, it is possible to efficiently irradiate the photographing area PA on the subject OB with illumination light.

  FIG. 3 is a block diagram of the camera 6. The CPU 10 controls the entire camera 6. When a power button provided on a camera body (not shown) is operated and the main switch SWMAIN is turned on, supply of power is started. When a shutter button (not shown) provided on the camera body is half-pressed, the photometry switch SWS is turned on. When the photometry switch SWS is turned on, the CPU 10 executes photometry processing and distance measurement processing. That is, the exposure value is calculated based on the input from the photometric device 11, and the aperture value, shutter speed, and charge accumulation time of the image sensor 13 necessary for photographing are calculated based on the exposure value. Further, a driving amount of a focusing lens (not shown) is calculated based on an input from the distance measuring device 12 and a driving signal is output to the focus driving circuit 14.

  When the shutter button is fully pressed, the release switch SWR is turned on. When the release switch SWR is turned on, the CPU 10 drives the shutter unit drive circuit 15 according to the aperture value calculated by the photometry process, and outputs a control signal to the image sensor drive circuit 16 according to the charge accumulation time. The shutter unit drive circuit 15 outputs a drive signal to the shutter unit 17 in accordance with the input control signal. The image sensor drive circuit 16 outputs a drive signal to the image sensor 13 in accordance with the input control signal. The image sensor 13 photoelectrically converts an optical image of a subject formed in the light receiving area and outputs an analog image signal. The A / D converter 18 A / D converts the analog image signal and outputs the digital image signal to the CPU 10.

  The digital image signal input to the CPU 10 is temporarily stored in the DRAM 19 as image data. The stored image data is appropriately read from the DRAM 19 when performing predetermined image processing. The EEPROM 20 stores various data for controlling the camera 6. When the main switch SWMAIN is turned on, various data are read from the EEPROM 20, stored in the RAM in the CPU 10, and used for control by the CPU 10.

  An LCD 21 provided on the back of the camera body is connected to the CPU 10. Various data such as shooting conditions and date are displayed on the LCD 21 under the control of the CPU 10.

  As a result of photometry by the photometry device 11, when it is determined that the amount of the subject light is insufficient, the CPU 10 outputs a flash emission control signal to the flash drive mechanism 22.

  FIG. 4 is a block diagram of the flash drive mechanism 22. A drive signal for controlling light emission of the blue LED 3 input from the CPU 10 is input to the PWM circuit 102, and a pulse signal having a predetermined pulse width is generated. That is, the PWM circuit 102 generates a pulse signal having a desired duty ratio and frequency in accordance with a control signal from the CPU 10. A pulse signal from the PWM circuit 102 is input to the drive pulse generation circuit 103. The drive pulse generation circuit 103 shapes the voltage value and current value of the pulse signal into predetermined values suitable for LED driving and outputs them as drive signals. A drive signal output from the drive pulse generation circuit 103 is output to the light emitting unit 2 via the power MOSFET 104 and the resistor R. Light emitted from the light emitting unit 2 is guided to the light projecting optical system 5. As a result, as described above, illumination light having the same radiation angle as the angle of view of the photographing optical system of the camera 6 is irradiated from the subject OB (see FIG. 2) via the light projection optical system 5.

  FIG. 5 is a diagram schematically showing a relative positional relationship between an illumination device to which the second embodiment according to the present invention is applied and a subject. In FIG. 5, the same members as those in the first embodiment are denoted by the same reference numerals. The light emitting unit 111 of the illuminating device 110 of 2nd Embodiment has five white LED112,113,114,115,116. These white LEDs are arranged so that the emitted light is uniformly incident on the diffusion plate 4. That is, as indicated by a broken line on the diffusion plate 4, the emitted light of the white LED 114 is incident on the center of the diffusion plate 4, and the emitted light of the white LEDs 112, 113, 115, 116 is near the four corners of the diffusion plate 5. Each is arranged to be incident. In FIG. 5, other configurations are the same as those of the first embodiment.

  By arranging a plurality of white LEDs as described above, a sufficient amount of light can be obtained even if LEDs having low luminance are used. If an LED with high luminance is used, a larger amount of light emission can be obtained. In addition, since the white LEDs are arranged at positions corresponding to the peripheral portion of the diffusion plate 5, it is possible to more effectively prevent the light amount from decreasing in the peripheral portion of the diffusion plate 5.

  In the first and second embodiments, a blue LED and a diffuser plate 4 containing a YAG-based fluorescent material are used in combination as a light emitting unit, and the light emitting unit is not limited to this. A white LED or a plurality of other single color LEDs and a diffusion plate having only a diffusion function may be combined. Needless to say, the aspect ratio of the diffusion plate 4 is changed according to the camera to be used. For example, the aspect ratio may be set to 4: 3 for a television camera and 16: 9 for a high-vision television camera.

It is a figure which shows typically the relative positional relationship of the illuminating device with which 1st Embodiment which concerns on this invention is applied, and a to-be-photographed object. It is a figure which shows typically the relative positional relationship of a light emission unit, a light projection optical system, and a to-be-photographed object. It is a block diagram of the camera used with a light emission unit. It is a block diagram of a flash drive mechanism. It is a figure which shows typically the relative positional relationship of the illuminating device with which 2nd Embodiment which concerns on this invention is applied, and a to-be-photographed object.

Explanation of symbols

1 Illumination device 2 Light-emitting unit 3 Blue LED
3a Support member 4 Diffuser 5 Projection optical system 6 Camera 10 CPU
22 Flash drive mechanism

Claims (1)

A semiconductor light emitting device;
A light projecting optical system for irradiating the subject with the emitted light emitted from the semiconductor light emitting element;
An illumination device comprising diffusion means interposed between the semiconductor light emitting element and the light projecting optical system, and diffusing the emitted light and guiding it to the light projecting optical system;
The diffusing means is disposed at a focal position of the light projecting optical system;
The entrance surface and the exit surface of the diffusing means exhibit a similar shape to the imaging area of the imaging means used with the illumination device,
The focal length of the light projecting optical system and the incident surface and the light exit surface of the diffusing unit so that the emission angle of the emitted light emitted from the light projecting optical system matches the angle of view of the photographing optical system of the photographing unit. A lighting device characterized in that the size of the lighting device is determined.

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