JP2006195031A - Auxiliary light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain satisfactory light distribution characteristics while securing a sufficient amount of light for photographing a static image, and to prevent a subject from being dazzled when framing is carried out. <P>SOLUTION: The auxiliary light source includes a first LED the allowable current of which is large and that emits light with high luminance, and a second LED the allowable current of which is small and that emits light with low luminance. When a moving image is photographed for framing, the first LED is driven with a small current and also the allowable current is made to flow in the second LED so that both of them emit light with the low luminance. Right before a static image is photographed in response to a release operation, the allowable current is made to flow in the first LED so that the first LED emits light with the high luminance. Then, the second LED is turned off. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an auxiliary light source device used in a photographing apparatus such as a digital camera.

  When the brightness of the subject is insufficient when photographing with a photographing device such as a camera using a photographic film or a digital camera photographing with an image sensor, the subject is irradiated with illumination light from the auxiliary light source device. As an auxiliary light source device, a strobe device that instantaneously emits light from a xenon tube in synchronization with photographing is widely used.

  An auxiliary light source device that employs a light emitting diode (hereinafter referred to as LED) as a light source is also known instead of the strobe device. An auxiliary light source device using an LED has a small number of parts and a simple circuit configuration, which is advantageous when it is incorporated into a small photographing device. In addition, some digital cameras perform framing of the subject while visually recognizing a through image displayed on a liquid crystal panel provided for the digital camera, but the LED is continuously displayed while framing is performed with such a digital camera. Some of them are designed to be able to perform framing and video recording in a dark place such as at night or indoors.

However, the amount of light of the auxiliary light source device using the LED as described above is small and insufficient. In order to increase the amount of light, a large forward current may be applied to the LED. However, if the forward current is excessive, the LED chip that constitutes the LED will be destroyed by its own heat generation. was there. In order to solve such problems, when shooting moving images with live view display, etc., a permissible current that can be continuously supplied to the LED is supplied to ensure a certain amount of light, and in response to the operation of the release button, When photographing an image, an auxiliary light source device is known that ensures a sufficient amount of light by flowing a large current exceeding an allowable current to an LED only at that moment (see Patent Document 1).
JP 2003-307771 A

  By the way, as LED which can flow a big electric current, although it is desirable that the size of an LED chip is larger than 0.4 mm square, for example, the size of the LED chip is very small. For this reason, when a large current of an allowable current is supplied to the LED, the light emission area with respect to the light output is very small and the light emission is high. When such a high-brightness LED is used to illuminate a subject (person), the subject is dazzled by illumination, and the eyes are closed or the face is turned away, so that an image with a favorable expression cannot be obtained. It was.

  In order to eliminate the above-described glare, one method is to dispose a diffusion plate in front of the LED. However, when a diffusing plate is provided, the light from the LED is diffused and reflected in the direction opposite to the subject, resulting in loss, which is not preferable.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an auxiliary light source device that achieves a preferable illumination state using a semiconductor light emitting element such as a light emitting diode.

  In order to achieve the above object, in the auxiliary light source device according to claim 1, a light source unit including a first semiconductor light emitting element having a large allowable current that can be continuously flowed and a second semiconductor light emitting element having a small allowable current, and a release. At the time of taking a still image of the photographing apparatus in response to the operation, a large current is passed through the first semiconductor light emitting element to emit high brightness, and the second semiconductor light emitting element is turned off or a current equal to or less than an allowable current is sent to emit low brightness. When not shooting a still image, the first semiconductor light emitting element is turned off or a current smaller than the allowable current is caused to emit light with low luminance, and a current less than the allowable current is caused to flow through the second semiconductor light emitting element to emit low luminance. Light emission control means.

  In the auxiliary light source device according to claim 2, the light emission control means is configured to flow an allowable current to the first semiconductor light emitting element during high luminance light emission. In the auxiliary light source device according to claim 3, an allowable current is allowed to flow to the second semiconductor light emitting element during low luminance light emission. Furthermore, in the auxiliary light source device according to claim 4, a plurality of second semiconductor light emitting elements are provided.

  In the auxiliary light source device according to claim 5, each of the first and second semiconductor light emitting elements is a light emitting diode, and the LED chip of the first semiconductor light emitting element is made larger than the second semiconductor light emitting element.

  The auxiliary light source device according to claim 6, wherein the photographing device is capable of taking a moving image and a still image, and a low current is caused by flowing a small current to one or both of the first and second semiconductor light emitting elements during moving image photographing. It is made to emit light.

  According to the present invention, when the framing is performed, for example, when shooting a still image, for example, when the first semiconductor light emitting element is turned off or has low luminance light emission, and the second semiconductor light emitting element is low luminance light emission, When taking a still image in response to a release operation, the first semiconductor light emitting element emits high luminance light and the second semiconductor light emitting element turns off or emits low luminance light. It is possible to illuminate the subject without feeling glare, and when photographing a still image, it is possible to photograph a natural expression while using the first semiconductor light emitting element as a main light source while improving light distribution characteristics. Further, by providing a plurality of second semiconductor light emitting elements, it is possible to increase the amount of light during framing without increasing the dazzling feeling.

  FIG. 1 shows the appearance of a mobile phone with a built-in digital camera embodying the present invention. The cellular phone 10 includes a receiver unit 12 and a transmitter unit 13 that are foldably connected by a hinge portion 11. The receiver unit 12 is provided with an antenna 14 and a receiver speaker. Further, the receiver unit 12 is provided with an LCD (liquid crystal display) 15 (see FIG. 2) on the inner surface side thereof.

  Further, the receiver unit 12 incorporates a camera unit 17 as a photographing device, and the photographing lens 18 is exposed on the back surface of the receiver unit 12. The camera unit 17 also includes an auxiliary light source device 20 that illuminates the subject. On the back side of the receiver unit 12, one first illumination window 21 and two second illumination windows 22 are provided in the vicinity of the photographing lens 18, and the auxiliary light source device 20 is connected to each illumination window 21, 22. Illuminate the subject with illumination light.

  On the inner surface side of the transmitter unit 13, a transmitter microphone 23, a key operation unit 24 for performing dial operations, various settings and operations, and the like are provided. By operating the key operation unit 24, it is possible to enter a shooting mode in which the camera unit 17 performs shooting. Under the shooting mode, the camera unit 17 normally operates in the through image mode to shoot a moving image, and displays the captured subject image on the LCD 15 as a through image. By observing this through image, the photographer can perform framing. If a release operation with a predetermined key of the key operation unit 20 is performed during the through image mode, the still image recording mode is entered in response to this, and the camera unit 17 captures one frame of the still image and obtains the obtained image data. Is recorded in the internal memory 25 (see FIG. 2).

  The principal part of the mobile phone 10 is shown in FIG. The system controller 30 controls each unit of the mobile phone 10 including the camera unit 17 based on an operation signal from the operation unit 24. The camera unit 17 includes an imaging unit 31 and a signal processing unit 32 in addition to the auxiliary light source device 20.

  The photographing unit 31 includes a photographing lens 18, an image sensor, a driver that drives the image sensor, and the like. In the photographing mode, the photographing unit 31 photographs a subject image with an image sensor through the photographing lens 18 and outputs a photographing signal obtained by photoelectrically converting the subject image. An imaging signal from the imaging unit 31 is sent to the signal processing unit 32. The signal processing unit 32 converts the photographic signal into image data by performing A / D conversion after performing correlated double sampling processing and amplification processing for removing noise on the photographic signal. Further, the signal processing unit 32 performs processing such as white balance adjustment, γ correction, data compression / decompression, and the like on the image data.

  In the live view mode under the shooting mode, the shooting unit 31 performs moving image shooting, and after the output shooting signal is converted into image data, white balance adjustment and γ correction are further applied to the LCD driver 34. Sent. The LCD driver 34 drives the LCD 15 based on the input image data. As a result, the subject image being photographed by the camera unit 17 is displayed as a moving image on the LCD 15, and the photographing range can be known by observing this. When the still image recording mode is set by the release operation of the operation unit 24, a still image for one frame is shot by the shooting unit 31 immediately after that. The image data of the still image shooting is recorded in the internal memory 25 after white balance adjustment, γ correction, and data compression are performed by the signal processing unit 32.

  The auxiliary light source device 20 includes a control circuit 35, a first drive circuit 36, a second drive circuit 37, a first LED (light emitting diode) 38 as a first semiconductor light emitting element, and a second LED 39 as a second semiconductor light emitting element. One first LED 38 and two second LEDs 39 are provided. The control circuit 35 constitutes a light source control means together with the first drive circuit 36 and the second drive circuit 37. In the control circuit 35, parameters corresponding to the through image mode and the still image mode are set by the system controller 30 in the shooting mode, and the LEDs 38.39 are connected via the drive circuits 36 and 37 according to the set parameters. Controls the light emission brightness.

  A first LED 38 is connected to the first drive circuit 36, and each second LED 39 is connected to the second drive circuit 37. As shown in FIG. 3, each LED 38, 39 constituting the light source unit is mounted on a substrate 41. Two second LEDs 38 are arranged at both ends at a predetermined interval, and the first LED 39 is located at the center. Has been placed. Further, the first LED 38 is arranged at a position facing the first illumination window 21, and each second LED 39 is arranged at a position facing the second illumination window 22, and the light from each LED 38, 39 corresponds to the corresponding illumination window. Irradiate the subject through. In addition, it is good for each 2nd LED39 to arrange | position with the space | interval more than the size of the LED chip.

  FIG. 4A shows the structure of the first LED 38, and FIG. 4B shows the structure of the second LED 39. The first LED 38 has a large LED chip 38a that emits light, and the second LED 39 has a small LED chip 39a. Since the size of the LED chip 38a is large in the first LED 38, the allowable current that can be continuously flowed is large, and it is possible to emit light with high luminance by flowing a large current. On the other hand, since the second LED 39 has a small size of the LED chip 38a, the allowable current that can be continuously flowed is small, and even when the allowable current flows, the second LED 39 emits light with low luminance.

  The first drive circuit 36 includes a resistor 36 a connected in series to the first LED 38 and a transistor 36 b that controls a current flowing through the first LED 38. The second drive circuit 37 includes a resistor 37 a connected in series to each second LED 39 and a transistor 37 b that controls a current flowing through each second LED 39. The control circuit 35 controls the light emission intensity of the LEDs 38 and 39 by increasing or decreasing the base currents of the transistors 36a and 37b.

  In the still image recording mode, that is, in the still image shooting mode, the control circuit 35 drives the first LED 38 with an allowable current that allows the allowable current to flow and emits light, and turns off the second LED 39 via the drive circuits 36 and 37. During live view mode, that is, when shooting a still image, the first LED 38 is driven at a low current that flows a current smaller than its allowable current, and the light emission brightness is lowered to such an extent that the subject does not feel glare. The second LED 39 is driven to drive the allowable current to allow the second LED 39 to emit light. As described above, the allowable current of the first LED 38 is a large current, and the allowable current of the second LED 39 is a small current. Therefore, when the allowable current is passed through the first LED 38, it is a large current and emits high luminance. As described above, when an allowable current is passed through the second LED 39, it is a low current light emission because it is a small current.

  In this example, the allowable current is passed as a large current flowing through the first LED 38, and the allowable current is passed as a small current flowing through the second LED 39. However, depending on the characteristics of the LEDs 38 and 39 and the required emission intensity, Can be changed.

  As described above, in the through image mode in which the auxiliary light source device 20 is configured to irradiate light on a subject for a long time, a plurality of first LEDs 38 having reduced luminance in this example, and light emission with an allowable current but low luminance light emission. Each of the second LEDs 39 is used to illuminate the subject with the necessary amount of light while avoiding glare. This is because when the light emitting area of the light source is small, such as an LED, it is less likely that the subject person feels dazzling when the same amount of light is obtained from a plurality of light sources and when the light source is spaced apart.

  On the other hand, when photographing using an auxiliary light source, it is preferable to illuminate with one light source in consideration of light distribution. For this reason, the first LED 38 emits light with high current with a large current to obtain a good light distribution and a sufficient amount of light. When the first LED 38 is brightly lit, the subject person feels dazzling, but there is no problem because the luminescence starts just before taking a still image. As the first LED 38, the LED chip size is desirably 0.4 mm square or more.

  The first LED 38 may be turned off in the through image mode, and the second LED 39 may be controlled to emit light with an appropriate luminance by driving with a current equal to or lower than the allowable current in the still image recording mode. Further, the number of the second LEDs 39 may be one, or three or more.

  Next, the operation of the above configuration will be described with reference to FIG. When shooting, the operation unit 24 is operated to select a shooting mode. Thereby, the through image mode under the photographing mode is set. When the live view mode is set, the system controller 30 sets the live view mode parameters in the control circuit 35.

  As a result, the first LED 38 is driven with a low current, and the second LED 39 is driven with an allowable current to illuminate the subject. Under this illumination, shooting of a moving image by the photographing unit 31 is started. The subject illuminated by the first and second LEDs 38 and 39 as described above is photographed by the image sensor of the photographing unit 31 through the photographing lens 18 and output as a photographing signal. The photographing signal is sent to the LCD driver 34 after being converted into image data by the signal processing unit 32. Image data is input to the LCD driver 34 one after another in synchronization with shooting by the shooting unit 31. Thereby, the subject image being shot is displayed on the LCD 15 as a moving image.

  The brightness required for shooting is ensured by the first LED 38 and each second LED 39 emitting light. However, a small current flows through the first LED 38, and the first LED 38 emits light with low brightness so as not to feel glare, and each second LED 39 emits light with an allowable current, but the allowable current of the second LED 39 is small. Since the 2LED 39 emits light with a brightness that does not feel glare, the subject does not feel glare. Therefore, it is possible to perform framing without causing the subject to turn away or distort the face, for example.

  The photographer operates the operation unit 24 to perform the release operation after framing while observing the subject image displayed on the LCD 15. When this release operation is performed, the still image recording mode is entered. Then, the parameters for the still image recording mode are set in the control circuit 35 by the system controller 30. As a result, the first LED 38 is driven with an allowable current through the first drive circuit 36 to emit light with high luminance, and the second LED 39 is turned off through the second drive circuit 37.

  As described above, after the first LED 38 emits light with high luminance and the second LED 3 is turned off, the system controller 30 gives a photographing instruction to the photographing unit 31. As a result, the image capturing unit 31 captures a still image for one frame. The imaging signal output by this imaging is converted into image data by the signal processing unit, and after various processing, the data is further compressed. This image data is recorded in the internal memory 25.

  At the time of still image shooting, the first LED 38 is driven with an allowable current to emit light with high brightness, so that the amount of light necessary for shooting is ensured and illumination with a single light source is ensured. can get. Of course, the subject may feel glare due to the high-intensity light emission of the first LED 38, but since the high-intensity light emission is started immediately before the photographing unit 31 shoots a still image, the subject is dazzled. For example, the photographing unit 31 can complete the photographing of the still image before the face is distorted or the face is turned away.

  The example shown in FIG. 6 shows an example in which a diffusion plate is provided in front of each second LED. In this example, a diffusion plate 45 is provided between the second illumination window 22 and the second LED 39. Thereby, the glare of the 2nd LED39 at the time of through image mode can be reduced more. As the diffusing plate 45, for example, a resin in which minute scatterers are mixed can be used.

  In the example of FIG. 6 described above, the diffusion plate is disposed on the front surface of the second LED. However, the diffusion plate may be disposed on the front surface of one or both of the first LED and the second LED. Moreover, you may comprise so that a diffusion plate may be inserted in an illumination window. Furthermore, when light that is not directed toward the subject among the light output from the LED, for example, light that diverges from the LED in the lateral direction is irradiated in the subject direction using the reflector, for example, a TiO2 pigment is applied to the reflector. Etc. may be given a diffusion function.

  In the above embodiment, the light emitting diode is used as the semiconductor light emitting element, but other semiconductor light emitting elements such as EL (electroluminescence) may be used. Further, although a case where a through image display is performed during moving image shooting has been described as an example, moving image shooting may be performed and recorded as moving image shooting. Further, in the above embodiment, the auxiliary light source device provided in the photographing device (camera unit) built in the mobile phone is described as an example. However, the auxiliary light source device of the present invention is a single digital camera as the photographing device. It may be built in a camera using a photographic film or may be used by being attached to a photographing apparatus.

It is a perspective view which shows the external appearance of the mobile phone incorporating the camera unit which has the auxiliary light source device which implemented this invention. It is a block diagram which shows the principal part structure of a mobile telephone. It is a perspective view which shows arrangement | positioning of each LED. It is explanatory drawing which shows the size of the LED chip of each LED. It is a flowchart which shows the control procedure of the auxiliary light source device sent in imaging | photography mode. The example which provided the diffusion plate in the front surface of 2nd LED is shown.

Explanation of symbols

17 Camera unit 20 Auxiliary light source device 35 Control circuit 36, 37 Drive circuit 38, 39 LED (light emitting diode)
38a, 39a LED chip

Claims (6)

In the auxiliary light source device that illuminates the subject to be photographed by the photographing device,
At the time of still image shooting of a light source unit having a first semiconductor light emitting element having a large allowable current that can be continuously flowed and a second semiconductor light emitting element having a small allowable current, and a photographing apparatus responding to a release operation, the first semiconductor light emitting element A high current is emitted by flowing a large current, and the second semiconductor light emitting element is turned off or a current equal to or lower than the allowable current is supplied to emit low luminance, and the first semiconductor light emitting element is turned off or allowed at a time other than when shooting a still image. An auxiliary light source device, comprising: a light emission control means for causing a low-intensity light emission by flowing a current smaller than the current, and causing the second semiconductor light-emitting element to emit a low-intensity light by flowing a current smaller than an allowable current.   The auxiliary light source device according to claim 1, wherein the light emission control unit causes an allowable current to flow to the first semiconductor light emitting element during high luminance light emission.   3. The auxiliary light source device according to claim 1, wherein the light emission control unit causes an allowable current to flow through the second semiconductor light emitting element during low luminance light emission. 4.   The auxiliary light source device according to claim 1, wherein a plurality of the second semiconductor light emitting elements are provided.   The first and second semiconductor light emitting elements are each a light emitting diode, and the LED chip of the first semiconductor light emitting element is larger than the second semiconductor light emitting element. Auxiliary light source device described in 1. 6. The photographing apparatus according to claim 1, wherein the photographing device is capable of photographing a moving image and a still image, and causes one or both of the first and second semiconductor light emitting elements to emit light with low luminance during the photographing of the moving image. The auxiliary light source device according to item 1.

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