JP2008225141A - Imaging apparatus and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus and an imaging method which are capable of picking up an excellent image by irradiating an object with illumination light highly accurately corresponding to the color temperature of a light source illuminating the object. <P>SOLUTION: Color temperature information of the light source in an image which is obtained by an imaging section 12 and displayed on a liquid crystal display section 52 is calculated by a digital signal processing section 42 and stored in a main memory 38. When a user operates a release switch, the color temperature information calculated just before the image is picked up is read from the main memory 38, to adjust a light emitting section 56 and the object is irradiated with the illumination light made of the color temperature corresponding to the light source, to pick up a desired image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and an imaging method, to which a light emitting unit that outputs illumination light whose color temperature can be adjusted is connected, and that illuminates the subject with the illumination light and images the subject.

  When a photograph is taken using a digital still camera under a situation where the amount of exposure is insufficient, such as at night, the illumination light is emitted from a light emitting unit connected to the camera.

  In this case, if the light emitting unit is composed of a xenon tube or the like, the output illumination light has a color temperature close to that of sunlight in the daytime. For example, shooting in the evening or shooting under room lighting is performed. In such a case, the color of the subject becomes unnatural, which causes a disadvantage that the atmosphere during shooting is impaired.

  Therefore, a flash device has been developed in which the light emitting unit is configured by R, G, and B LEDs, and the illumination light having a desired color temperature can be irradiated to the subject by adjusting the light quantity ratio of each LED. (See Patent Documents 1 and 2).

  In the technique disclosed in Patent Document 1, when the release switch of the image pickup apparatus is half-pressed, the color temperature sensor of the light-emitting unit connected to the image pickup apparatus is used to detect the color temperature of the object field, and the color The light quantity ratio of the R, G, and B LEDs is controlled so as to be the temperature.

  Further, in the technique disclosed in Patent Document 2, the color temperature of the object scene is calculated based on the image of the subject acquired by the imaging device, and the light emitting unit connected to the imaging device is configured to obtain the color temperature. The light quantity ratio of the R, G, and B LEDs is controlled.

JP 2002-116481 A JP 2004-242123 A

  However, in these conventional techniques, since the relationship between the timing for measuring the color temperature and the timing for shooting the subject is not clear, for example, when the time interval from the measurement of the color temperature to the shooting is increased. The illumination light corresponding to the color temperature of the object scene at the time of shooting may not be able to be applied to the subject.

  The present invention has been made to solve the above-described problems, and can illuminate a subject with illumination light corresponding to the color temperature of a light source that illuminates the subject with high accuracy, thereby capturing a good image. An object is to provide an imaging apparatus and an imaging method.

In the imaging apparatus of the present invention, a light emitting unit that outputs illumination light whose color temperature can be adjusted is connected, and the subject is irradiated with the illumination light to capture an image of the subject.
An imaging unit for acquiring image information of the subject;
A color temperature information calculation unit that calculates color temperature information of a light source that illuminates the subject at predetermined time intervals based on image information of the subject acquired by the imaging unit;
A color temperature information storage unit for storing the calculated color temperature information;
A color temperature adjusting unit that adjusts the color temperature of the illumination light based on the color temperature information stored in the color temperature information storage unit;
The color temperature information related to the light source that illuminates the subject is read from the color temperature information storage unit to adjust the color temperature of the illumination light, and the adjusted illumination An image of the subject is captured by irradiating the subject with light.

Further, the imaging method of the present invention is an imaging method for capturing an image of the subject by irradiating the subject with the illumination light from a light emitting unit that outputs illumination light with adjustable color temperature.
Obtaining image information of the subject and calculating color temperature information of a light source that illuminates the subject based on the image information at a predetermined time interval;
Adjusting the color temperature of the illumination light based on the color temperature information relating to the light source that illuminates the subject when capturing an image of the subject; and
Irradiating the subject with the adjusted illumination light to capture an image of the subject;
It is characterized by comprising.

  In this case, a good image can be taken by adjusting the color temperature of the illumination light using the color temperature information calculated immediately before photographing among the color temperature information calculated at a predetermined time interval.

  Further, by adjusting the color temperature of the illumination light based on the average information of the calculated plurality of color temperature information, for example, even when an image is captured while moving the imaging device, a good image can be obtained. .

  Also, by calculating the color temperature information based on the image information acquired by the imaging unit and displayed on the display unit, it is possible to obtain highly accurate color temperature information corresponding to the subject to be imaged.

  The light emitting unit that outputs illumination light includes light emitting elements of three colors of R, G, and B, and the color temperature can be adjusted by the light quantity ratio of the illumination light output from each light emitting element.

  In the imaging apparatus and imaging method of the present invention, the color temperature information of the light source that illuminates the subject is calculated at predetermined time intervals based on the image of the subject acquired by the imaging unit, and illumination is performed according to the color temperature information immediately before imaging. By adjusting the color temperature of the light, it is possible to illuminate the subject with illumination light adjusted with high accuracy corresponding to the light source that illuminates the subject, and to capture a good image.

  FIG. 1 is a block diagram showing the configuration of a digital still camera 10 to which the imaging apparatus of the present invention is applied.

  The digital still camera 10 controls the imaging unit 12 that acquires image information of a subject, a flash device 14 that is connected to the digital still camera 10 and emits illumination light to the subject, and the imaging unit 12 and the flash device 14. And a signal processing circuit. The flash device 14 can be integrated into the digital still camera 10 or can be detachable.

  The imaging unit 12 includes a photographic lens 16 and a solid-state imaging device 18 that converts image information of a subject into an electrical signal. Between the photographic lens 16 and the solid-state imaging device 18, an aperture 20, an infrared cut filter 22, and an optical low-pass. A filter 24 is provided. The optical low-pass filter 24 is a filter that cuts a spatial frequency component equal to or higher than the Nyquist frequency included in the optical information. As the solid-state image sensor 18, a two-dimensional CCD sensor or a two-dimensional CMOS sensor in which pixels are arranged in a honeycomb or Bayer system can be used.

  The signal processing circuit includes a CPU 26 that controls the entire digital still camera 10. An operation unit 27 is connected to the CPU 26, and various processes including setting of imaging conditions are executed according to instruction information from the user input via the operation unit 27. The CPU 26 controls the flash device 14 to irradiate a subject with illumination light having an appropriate color temperature and light amount, which will be described later, and performs AF control by controlling the lens driving unit 28 to drive the photographing lens 16. AE control is performed by controlling the aperture drive unit 30 to drive the aperture 20. Further, the CPU 26 drives the solid-state imaging device 18 by controlling the imaging device driving unit 32, and obtains R, G, and B color signals from the image information of the subject acquired through the photographing lens 16. The R, G, and B color signals that are analog signals acquired by the solid-state imaging device 18 are processed by the analog signal processing unit 34 and then converted into digital signals by the A / D converter 36.

  In addition, the CPU 26 includes a memory control unit 40 (color temperature information storage unit) that controls a main memory 38 that stores image information that is a digital signal acquired by the imaging unit 12 and color temperature information of a subject that will be described later. A digital signal processing unit 42 (color temperature information calculation unit) that calculates color temperature information of a light source by performing desired digital signal processing on information, a compression / decompression processing unit 44 that performs compression / decompression processing of image information, and acquisition The acquired image information is acquired by the integration unit 46 that integrates the R, G, and B color signals for each color signal and supplies the digital signal processing unit 42, the external memory control unit 50 that controls the removable recording medium 48, and the imaging unit 12. A display control unit 54 for controlling the liquid crystal display unit 52 that displays image information in real time is connected thereto.

  The signal processing circuit described above may be configured by individual circuit elements, or may be configured as a single solid-state imaging device using LSI manufacturing technology on the same semiconductor substrate as the solid-state imaging element 18. .

  FIG. 2 is a block diagram showing the configuration of the flash device 14. The flash device 14 includes a light emitting unit 56 that irradiates illumination light to the subject, a light receiving unit 58 that receives illumination light reflected by the subject, and a CPU 60 that controls the entire flash device 14.

  CPU 60 controls converter 62 to boost the voltage of battery 64 and charge capacitor 66. The capacitor 66 is connected in parallel with an LED 68 that outputs R illumination light, an LED 70 that outputs G illumination light, and an LED 72 that outputs B illumination light. Switching transistors 74, 76, and 78 are connected in series to the LEDs 68, 70, and 72 (light emitting elements) constituting the light emitting unit 56.

  The CPU 60 (color temperature adjustment unit) switches each of the switching transistors 74, 76, 78 based on the light emission signal generated by operating the release switch and the color signal of the illumination light calculated by the digital signal processing unit 42. Output an RGB control signal that turns ON for a predetermined time. With this RGB control signal, the color temperature of the illumination light output from the light emitting unit 56 is adjusted.

  Further, the phototransistor 82 constituting the light receiving unit 58 is connected to the CPU 60 via the dimming circuit 80. The dimming circuit 80 compares the light amount signal of the illumination light detected by the phototransistor 82 with the light emission amount adjustment signal supplied from the CPU 60, and stops the light emission of the LEDs 68, 70, 72 when these signals match. An issue OFF signal is output to the CPU 60.

  The digital still camera 10 of the present embodiment is basically configured as described above. Next, the operation will be described based on the flowchart shown in FIG.

  When the power of the digital still camera 10 is turned on (step S1) and the still image shooting mode is selected from the operation unit 27, the CPU 26 drives the imaging unit 12 to acquire an image of the subject (step S2).

  That is, light from the subject is guided to the solid-state image sensor 18 through the photographing lens 16, the diaphragm 20, the infrared cut filter 22, and the optical low-pass filter 24, and is output from the R, G, and B color signals by the image sensor drive unit 32. Is converted into an electrical signal. The CPU 26 drives the lens driving unit 28 to perform AF control, and drives the aperture driving unit 30 to perform AE control.

  The subject image information converted into the electrical signal is processed by the analog signal processing unit 34 and then converted into a digital signal by the A / D converter 36. Then, the acquired image is displayed by the display control unit 54 on the liquid crystal display unit. 52 (step S3). The user determines the composition of the still image while checking the displayed image.

  On the other hand, the integrating unit 46 integrates the R, G, B color signals constituting the image of one field displayed on the liquid crystal display unit 52 for each color signal, and supplies each integrated value to the digital signal processing unit 42. (Step S4). The digital signal processing unit 42 is a signal ratio R / G between the integrated value of the R color signal and the integrated value of the G color signal, and the signal of the integrated value of the B color signal and the integrated value of the G color signal. The ratio B / G is calculated (step S5), and the color temperature of the light source that illuminates the subject is specified based on these signal ratios R / G and B / G (step S6).

  As a method of specifying the color temperature of the light source, for example, a color temperature range is set for each type of light source with the signal ratio R / G on the horizontal axis and the signal ratio B / G on the vertical axis. A method of specifying the color temperature of the light source from the color temperature range to which the ratios R / G and B / G belong can be employed (see JP 2000-224608 A).

  The color temperature information of the light source specified as described above is stored in the main memory 38 by the memory control unit 40 (step S7). The color temperature information calculation process is repeatedly performed at predetermined time intervals until the user operates the release switch to capture a still image of the subject (step S8).

  For example, as illustrated in FIG. 4, the display control unit 54 performs image F (N-5), image F (N-4), image F (N-3), image F (N-2), and image of one field. Each time F (N-1) is displayed on the liquid crystal display unit 52, the color temperature information of each image is calculated and stored in the main memory 38. Note that the color temperature information may be calculated not for each field but for a predetermined plurality of fields.

  Next, when the user operates the release switch to instruct image capture, the digital signal processing unit 42 reads out the color temperature information of the image F (N−1) calculated immediately before the image capture from the main memory 38 ( In step S9), signal ratios R / G and B / G corresponding to the color temperature information are calculated (step S10), and the ratios of the color signals R, G and B are obtained and set in the CPU 60 of the flash unit 14 (step S10). S11).

  Therefore, when a light emission signal based on the operation of the release switch is supplied to the CPU 60 of the flash device 14, the CPU 60 switches the switching transistors 74, 76, 78 to the light emitting unit 56 at a predetermined ratio corresponding to the color temperature of the light source. An RGB control signal for turning ON is supplied. In this case, the electric charge accumulated in the capacitor 66 is discharged through the LEDs 68, 70, 72, and the subject is irradiated with illumination light corresponding to the color temperature of the light source calculated immediately before photographing (step S12). At the same time, the image F (N) is imaged by the imaging unit 12 and stored in the main memory 38 (step S13). The image F (N) can be stored in the recording medium 48 by the external memory control unit 50 after being compressed by the compression / decompression processing unit 44.

  In this case, the captured image F (N) is illuminated with illumination light adjusted according to the color temperature of the light source calculated from the image related to the user's composition displayed on the liquid crystal display unit 52 immediately before imaging. As a result, it is possible to obtain a good image without a sense of incongruity.

  On the other hand, in the above description, the color temperature of the illumination light is adjusted based on the image of one field acquired immediately before imaging, but the color temperature of the illumination light is adjusted based on the images of a plurality of fields. You may do it.

  That is, as shown in the flowchart of FIG. 5, the digital still camera 10 is turned on (step S21), the image pickup unit 12 is driven to acquire the subject image, and the image is displayed on the liquid crystal display unit 52 to set the composition. On the other hand (steps S22 and S23), the R, G, and B color signals are integrated every n fields of the displayed image (step S24). For example, assuming that n = 1, the color signals of the image F (N-5), the image F (N-3), and the image F (N-1) are integrated.

  Next, signal ratios R / G and B / G are calculated using the integrated color signal (step S25), and the color temperature of the light source in each field is specified (step S26). Then, the color temperature information of the light source in the specified plurality of fields is stored in the main memory 38 (step S27). These processes are repeated until the user operates the release switch (step S28).

  Next, when the user operates the release switch to capture an image, the color temperature information of a plurality of fields calculated immediately before imaging is read from the main memory 38 (step S29), and the average information of the color temperature information is obtained. Calculate (step S30). Then, the signal ratios R / G and B / G are calculated based on the calculated average information (step S31), and the ratios of the color signals R, G, B are obtained and set in the CPU 60 of the flash unit 14 (step S32). . The flash unit 14 irradiates the subject with illumination light adjusted according to the set ratio (step S33), and a desired still image is captured by the imaging unit 12 (step S34).

  In this case, since the illumination light is adjusted based on the average information of the color temperature information of the light sources in a plurality of fields calculated immediately before imaging, for example, the user performs imaging while panning the digital still camera 10. Even in such a case, illumination light having an inappropriate color temperature is not generated, and a good image can be obtained.

  In addition, this invention is not limited to embodiment mentioned above, Of course, it can change freely in the range which does not deviate from the main point of this invention.

It is a block diagram of the digital still camera. It is a block diagram of the configuration of a flash device incorporated in a digital still camera. It is an operation | movement flowchart of a digital still camera. It is explanatory drawing of the field utilized in order to specify the color temperature of a light source. It is an operation | movement flowchart in other embodiment of a digital still camera.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital still camera 12 ... Imaging part 14 ... Flash apparatus 18 ... Solid-state image sensor 26, 60 ... CPU 38 ... Main memory 42 ... Digital signal processing part 46 ... Accumulation part 52 ... Liquid crystal display part 56 ... Light emission part 58 ... Light receiving part 66 ... Capacitors 68, 70, 72 ... LED 80 ... Dimming circuit 82 ... Phototransistor

Claims (6)

In an imaging device to which a light emitting unit that outputs illumination light whose color temperature can be adjusted is connected, and the subject is irradiated with the illumination light to capture an image of the subject.
An imaging unit for acquiring image information of the subject;
A color temperature information calculation unit that calculates color temperature information of a light source that illuminates the subject at predetermined time intervals based on image information of the subject acquired by the imaging unit;
A color temperature information storage unit for storing the calculated color temperature information;
A color temperature adjusting unit that adjusts the color temperature of the illumination light based on the color temperature information stored in the color temperature information storage unit;
The color temperature information related to the light source that illuminates the subject is read from the color temperature information storage unit to adjust the color temperature of the illumination light, and the adjusted illumination An image pickup apparatus that irradiates the subject with light and picks up an image of the subject. The apparatus of claim 1.
The color temperature adjusting unit reads the color temperature information calculated immediately before imaging from the color temperature information storage unit and adjusts the color temperature of the illumination light. The apparatus according to claim 1 or 2,
The color temperature information storage unit stores a plurality of the color temperature information calculated at a predetermined time interval,
The color temperature adjusting unit adjusts a color temperature of the illumination light based on average information of the plurality of pieces of color temperature information. The device according to any one of claims 1 to 3,
The display unit displays an image of the subject acquired by the imaging unit, and the color temperature information calculation unit is based on the image information displayed on the display unit, and the color temperature information of the light source that illuminates the subject An imaging device characterized by calculating In the apparatus of any one of Claims 1-4,
The light-emitting unit includes R, G, and B light-emitting elements capable of adjusting light emission amounts. In an imaging method for capturing an image of the subject by irradiating the subject with the illumination light from a light emitting unit that outputs illumination light with adjustable color temperature,
Obtaining image information of the subject and calculating color temperature information of a light source that illuminates the subject based on the image information at a predetermined time interval;
Adjusting the color temperature of the illumination light based on the color temperature information relating to the light source that illuminates the subject when capturing an image of the subject; and
Irradiating a subject with the adjusted illumination light to capture an image of the subject;
An imaging method comprising:

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