JP2007189300A - Imaging apparatus, imaging method, and imaging program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus, an imaging method, and an imaging program for controlling the amount of emission of each LED in strobe photographing. <P>SOLUTION: In strobe photographing, the amount of emission of each LED is controlled to align the output of R, G, B at the output of an image pickup device, and the need for multiplication processing in WB is eliminated, thus suppressing the deterioration of S/N in moving pictures and still images where no unnecessary multiplication processing is performed to the R, B signals. For preventing a decrease in strobe emission luminance due to a decrease in the amount of emission of the G LED having high contribution as a luminance signal component, the amount of emission of R, B LEDs is increased for controlling so that the output of R, G, B in the image pickup element becomes uniform, thus maintaining strobe arrival distance and suppressing deterioration in S/N simultaneously. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an imaging device, an imaging method, and an imaging program, and more particularly to an imaging device, an imaging method, and an imaging program that control the light emission amount of each LED during flash photography.

  Conventional strobe units are generally devices composed of a xenon tube lamp, a main capacitor, and a high voltage charging circuit. However, this configuration is a hindrance to cost reduction and downsizing of devices in a compact camera intended for consumers. In recent years, attention has been focused on LED (Light Emitting Diode) strobes.

  Conventionally, in a strobe device having an LED element, a large amount of electric charge is discharged in a short time, so that its use is limited to photographing a still image. However, in recent years, the sensitivity of photographic films and the like has improved, and high-sensitivity films such as ISO sensitivities 800 to 1600 have become generally available. Further, even in an electronic camera such as a digital still camera, the sensitivity of an image sensor such as a CCD is improved, and a large amount of light as in a conventional strobe is not necessarily required for subject illumination. Therefore, continuous lighting and pulse lighting can be performed by the LED element, and it can be used as auxiliary light for moving image shooting.

  The LED used in the strobe device includes a method of combining R, G, and B LED elements and a method of combining a blue to ultraviolet LED element and a phosphor. The former method has a feature that the control of the emission color is good because the emission amount can be controlled independently for each color.

  In Patent Document 1, a light emitting means capable of emitting strobe light toward a subject, a side color means for detecting a color temperature of ambient light, and a color temperature of strobe light according to the color temperature of ambient light, By providing control means for controlling the color temperature of the light that illuminates the light to substantially equal the spectral sensitivity design value of the image sensor, a natural color image can be obtained without providing a white balance circuit and a vertical edge extraction circuit. Strobe devices that can be obtained have been proposed.

Japanese Patent Application Laid-Open No. 2004-228688 has an illumination device having a light source configured by arranging a plurality of light emitting diodes that emit light for each of the three primary colors red, green, and blue, and the illumination device and the document are moved relative to each other on the document. In a color image reading apparatus that reads the image of the image with a color CCD, the color image reading apparatus has a color balance calibrating means including a control device that controls the driving of the light source, and a light amount detecting means. Each LED has a light guide that regulates the spread of the speed of light, and each LED is simultaneously lit by a lighting driving device for each color based on the current value stored in advance in the storage device in the control device, and each color is mixed. The color balance calibrating means is arranged so as to illuminate the original surface, and directly or indirectly detects the illumination light quantity from the illuminating device for each of R, G, and B by the light quantity detection means. By rewriting the current value stored in the storage device as necessary to achieve a color balance of Proposed.
Japanese Patent No. 3574480 JP 2004-320603 A

  However, the above invention has the following problems.

  The above-mentioned invention is a technology that eliminates the above-mentioned problems by using an LED element for strobe light, eliminating the need for a booster circuit to several hundred volts, a main capacitor, and a charging circuit for the main capacitor. is there.

  The strobe device described in Patent Document 1 does not require white balance by controlling the color of strobe light, but cannot suppress S / N degradation that occurs in an image sensor or the like. Another difference is that an arc tube, a color filter, and a transmissive liquid crystal are used as means for controlling the color temperature.

  The color image reading device described in Patent Document 2 controls white balance by LEDs, but is limited to the color image reading device and cannot suppress S / N deterioration that occurs in an image sensor or the like.

  Therefore, the present invention controls the light emission amount of each LED at the time of flash photography, aligns the output of R, G, and B at the output part of the image sensor, and eliminates the need for multiplication processing in WB, so that the signal of R and B can be obtained. In addition, an object of the present invention is to propose an imaging apparatus that can suppress S / N degradation of moving images and still images because no extra multiplication processing is performed.

  According to the first aspect of the present invention, there is provided a light projecting means for irradiating a subject by combining light emitting elements of a plurality of colors, a control means for controlling a light emission amount of the light emitting element, and a color for photographing a subject irradiated by the light emitting element. In an imaging apparatus having an imaging optical system including an imaging element, when shooting an image by projecting the light emitting element, the control unit is configured to select each color of the color imaging element corresponding to a gray or white portion in the subject. The light emission amount of the light emitting element is controlled so that the signal output levels are equal.

  According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, when the light emitting element is projected to capture an image, the control unit is configured to control the color corresponding to a gray or white portion in the subject. The light emission amount of the light emitting element is controlled so as to reduce the output level difference of each color signal of the image pickup element.

  According to a third aspect of the present invention, in the imaging apparatus according to the first or second aspect, the light projecting means is a combination of R, G, and B light emitting elements, and projects the light by projecting the light emitting elements. In this case, the control means controls the light emission amount of the G light emitting element so that the output level of each color signal of the color imaging element corresponding to the gray or white portion in the subject becomes equal. It is characterized by doing.

  According to a fourth aspect of the present invention, in the imaging apparatus according to the first or second aspect, the light projecting means is a combination of R, G, and B light emitting elements, and projects the light by projecting the light emitting elements. In this case, the control means controls the light emission amounts of the R and B light emitting elements so that the output levels of the color signals of the color imaging elements corresponding to the gray or white portion in the subject are equal. It is a characteristic.

  According to a fifth aspect of the present invention, there is provided a light projecting means for irradiating a subject by combining light emitting elements of a plurality of colors, a control means for controlling a light emission amount of the light emitting element, and a color for photographing a subject irradiated by the light emitting element. An imaging method of an imaging apparatus including an imaging optical system including an imaging element, wherein when the light emitting element is projected to capture an image, the control unit corresponds to the gray or white portion in the subject It has a step of controlling the light emission amount of the light emitting element so that the output level of each color signal of the color image sensor becomes equal.

  According to a sixth aspect of the present invention, there is provided a light projecting means for irradiating a subject by combining light emitting elements of a plurality of colors, a control means for controlling the light emission amount of the light emitting element, and a color for photographing the subject irradiated by the light emitting element. An imaging program of an imaging apparatus including an imaging optical system including an imaging element, wherein when the light emitting element is projected to capture an image, the control unit corresponds to the gray or white portion in the subject It has a process for controlling the light emission amount of the light emitting element so that the output level of each color signal of the color image sensor becomes equal.

  The present invention controls the amount of light emitted from each LED during strobe shooting, aligns the R, G, and B outputs at the output section of the image sensor, and eliminates the need for multiplication processing in the WB, thereby adding extra to the R and B signals. Therefore, S / N deterioration of moving images and still images can be suppressed.

  Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described.

  First, the system configuration of the imaging apparatus according to the present embodiment will be described with reference to FIG.

  The system configuration of the imaging apparatus according to the present embodiment includes an imaging optical system 100, an optical system driving unit 105, an imaging element driving unit 106, an image processing unit 107, an image display unit 108, an image buffer memory 109, an image recording I / F. Unit 110, program memory 111, operation unit 112, control unit 113, LED power source / light emission amount control unit 114, and R, G, and B LEDs (115 to 117).

  The photographing optical system 100 includes a lens 101, a diaphragm 102, a filter 103, and an image sensor 104. Further, the image processing unit 107 includes a CDS 119, a PGA 120, an A / D 121, and a WB 122.

  The brightness control of each of the R, G, and B LEDs (115 to 117) is performed from the control unit 113 through the LED power source / light emission amount control unit 114. The LED power supply / light emission amount control unit 114 includes a constant current power supply circuit and a current value switching circuit for each LED.

  The filter 103 has an optical low-pass filter for cutting off high-frequency components of the subject to reduce false colors and moire fringes, and an infrared cut filter for cutting off wavelengths other than visible light for accurate color reproduction. Configured. A dotted line shown in FIG. 2 is a general spectral sensitivity characteristic of the filter 103. Also, the solid line shown in FIG. 2 is the spectral sensitivity characteristic of the image sensor 104. Since the spectral sensitivity characteristic of a normal image sensor matches the human specific visual sensitivity, the G spectral sensitivity is high. For this reason, when a white subject is photographed with daylight, the output level of G may be 1.5 times or more the output level of R · B in the level of the output signal of the image sensor. The filter cuts a wavelength region of 650 nm or more and 400 nm or less.

  In a normal imaging device, the output of the imaging element 104 is sampled in units of pixels in the CDS 119 in the image processing unit 107 and reproduced as an analog signal, amplified to a predetermined value by the PGA 120, and digitally converted by the A / D 121. Thus, white balance processing is performed at WB122. Specifically, in the conventional imaging apparatus, S / N deterioration is suppressed by lowering the multiplication value in the multiplication process for the R signal and the B signal performed in the WB 122.

  In the present embodiment, the light emission amount of each LED is controlled. As a specific method, light emission luminance control and light emission time control can be considered. As a method of controlling the light emission luminance, there are a method of controlling by the value of current flowing through the LED and a control method of controlling the number of light emitting elements. Further, as a method for controlling the light emission time, there is a method of changing the light emission time within the exposure time of the photographing apparatus for the purpose of reducing the power load of the apparatus. In the present embodiment, a method of controlling the light emission amount of the LED by controlling the current supplied to each of the R, G, and B LEDs will be described, but the present invention is not limited to this.

  Next, the relative light emission intensity of each LED (115 to 117) in the image pickup apparatus according to the present embodiment and the output levels of R, G, and B output from the image sensor 104 will be described with reference to FIGS. To do.

  3A and 4A show the light emission intensity of each LED at the time of photographing in the conventional imaging device and the imaging device according to the present embodiment. 3B and 4B show output levels of the image sensor corresponding to the gray (or white) region of the subject at the time of shooting in the conventional imaging device and the imaging device according to the present embodiment.

  In the conventional imaging device, the LED emits white light in the vicinity of 3500 to 6500K, and the relative light emission intensity at that time is assumed to be r1, g1, and b1. As shown in FIG. 3A, when light is emitted under this condition, the output level shown in FIG. 3B is obtained from the image sensor by multiplying the achromatic object by the spectral sensitivity characteristics of FIG. 3A and FIG. Will be output. That is, since G is dominant in the spectral sensitivity, the relationship of V1g >> V1r, V1b is established, and the WB 122 needs to multiply the R output signal and the B output signal by V1g / V1r and V1g / V1b.

  On the other hand, in the imaging apparatus according to the present embodiment, each LED (115 to 117) emits light so that the relative light emission luminance of each LED is r1 <r2, g1> g2, and b1 <b2. The image sensor output shown in (b) is obtained. According to this photographing method, the output voltages of R, G, and B are more uniform than those during normal photographing. Therefore, V2g / V2r and V2g / V2b, which are multiplication values of the R output signal and the B output signal in WB122, satisfy the relationship of V2g / V2r <V1g / V1r, V2g / V2b <V1g / V1b, and S / N Achieves suppression of deterioration.

  The spectral sensitivity of an image sensor used in a normal digital camera is governed by G. When a white object is photographed under a daylight light source, the G output is larger than the R and B outputs at the image sensor output. It becomes. By applying multiplication processing in WB to the output of R, G, and B, which are irregular, a level of each color becomes uniform and a moving image or a still image that is a white object is obtained. Therefore, in shooting under normal color temperature, the output of R, G, and B has a higher multiplication rate in the image processing unit than the G output, and quantization error and S / N degradation caused by multiplication processing Occurs. However, as described above, by controlling the light emission amount of each LED at the time of flash photography and aligning the output of R, G, and B at the output part of the image sensor, the multiplication processing in WB is not required, so Since unnecessary multiplication processing is not performed on the signal, it is possible to suppress S / N deterioration of the moving image and the still image.

  Also, when aligning the R, G, and B outputs by controlling the light emission amount of the LEDs, the light emission amount of the G LED is relatively set in consideration of the spectral sensitivity of the image sensor and the filter that are normally used. Must be less than the amount of light emitted. However, if the light emission amount of the G LED having a high contribution ratio as the luminance signal component is reduced, the strobe light emission luminance becomes dark and the strobe reaching distance becomes short. That is, there is a contradictory relationship between the strobe range and the suppression of S / N degradation. Therefore, in consideration of the degree of influence on both image pickup devices, the output of the R / B LEDs is increased and the output of the R / G / B of the image pickup device is made uniform in order to prevent a significant decrease in the strobe range. It can also be controlled.

It is a block diagram which shows the system configuration | structure of the imaging device concerning this embodiment. It is a figure which shows the spectral sensitivity characteristic of an image pick-up element and a filter. (A) is a figure which shows the relative light emission intensity of LED at the time of imaging | photography with the conventional imaging device, (b) is a figure which shows CCD output voltage. (A) is a figure which shows the relative light emission intensity of LED at the time of imaging | photography with the imaging device concerning this invention, (b) is a figure which shows CCD output voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image | photographing optical system 101 Lens 102 Diaphragm 103 Filter 104 Image pick-up element 105 Optical system drive part 106 Image pick-up element drive part 107 Image processing part 108 Image display part 109 Image buffer memory 110 Image recording I / F part 111 Program memory 112 Operation part 113 Control Unit 114 LED Power Supply / Light Emission Control Unit 115 Red LED
116 Green LED
117 Blue LED
119 CDS
120 PGA
121 A / D
122 WB

Claims (6)

Light projecting means for illuminating a subject by combining light emitting elements of a plurality of colors, control means for controlling the light emission amount of the light emitting elements, and a photographing optical system including a color imaging element for photographing a subject illuminated by the light emitting elements, In an imaging apparatus having
When photographing the image by projecting the light emitting element, the control means controls the light emitting element so that the output level of each color signal of the color imaging element corresponding to the gray or white portion in the subject becomes equal. An imaging apparatus characterized by controlling a light emission amount.   When shooting the image by projecting the light emitting element, the control means reduces the output level difference of each color signal of the color imaging element corresponding to the gray or white portion in the subject. The image pickup apparatus according to claim 1, wherein the light emission amount is controlled. The light projecting means is a combination of R, G and B light emitting elements,
When shooting the image by projecting the light emitting element, the control means is configured so that the output level of each color signal of the color imaging element corresponding to the gray or white portion in the subject becomes equal. The imaging apparatus according to claim 1, wherein the light emission amount of the light emitting element is controlled. The light projecting means is a combination of R, G and B light emitting elements,
When shooting the image by projecting the light emitting element, the control means is configured to adjust the output of each color signal of the color imaging element corresponding to the gray or white portion in the subject to be equal. The imaging apparatus according to claim 1, wherein the light emission amount of the B light emitting element is controlled. Light projecting means for illuminating a subject by combining light emitting elements of a plurality of colors, control means for controlling the light emission amount of the light emitting elements, and a photographing optical system including a color imaging element for photographing a subject illuminated by the light emitting elements, An imaging method for an imaging apparatus having
When photographing the image by projecting the light emitting element, the control means controls the light emitting element so that the output level of each color signal of the color imaging element corresponding to the gray or white portion in the subject becomes equal. An imaging method comprising a step of controlling a light emission amount. Light projecting means for illuminating a subject by combining light emitting elements of a plurality of colors, control means for controlling the light emission amount of the light emitting elements, and a photographing optical system including a color imaging element for photographing a subject illuminated by the light emitting elements, An imaging program for an imaging apparatus having
When photographing the image by projecting the light emitting element, the control means controls the light emitting element so that the output level of each color signal of the color imaging element corresponding to the gray or white portion in the subject becomes equal. An imaging program comprising a process for controlling a light emission amount.

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