JP2006259171A - Imaging apparatus, digital still camera, and imaging method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To selectively use image quality precedence or luminance precedence according to distance distribution of an object, object luminance in the object in an angle of field to obtain successful image quality with a small amount of energy depending on a scene. <P>SOLUTION: This image forming apparatus has light emitting diodes 1a, 1b, 1c in three colors of R, G, B used as illumination light sources, an illumination means for adjusting luminance of the respective light emitting diodes; a ranging means 29 for ranging a plurality of areas in the angle of field; a color temperature measurement means for measuring color temperature of the object; a luminance measurement means for measuring luminance of the plurality of areas in the angle of field; and a main control means 10 for controlling drive of the light emitting diodes in three colors according to distance distribution of the object, the object luminance and the color temperature to adjust the color temperature of the illumination means. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging device, a digital still camera, and an imaging method that use R, G, and B light emitting diodes as illumination light sources.

  Patent Documents 1, 2, and 3 describe imaging apparatuses that use a xenon tube as an illumination light source and control the illumination light source. On the other hand, in recent years, high-luminance LEDs of the three primary colors R, G, and B have been put into practical use as illumination means, and have been used in auxiliary light devices for mobile phones with cameras.

  When comparing the auxiliary light device using a conventional xenon tube that has been used as auxiliary light for cameras with LED auxiliary light, the former charges a large-capacity capacitor over a few seconds and releases the charge in an instant. While the latter can be used only for still image shooting, the latter basically has no concept of charging time, and can be lit continuously or pulsed, so it can be used as auxiliary light for moving images. There are advantages such as being able to.

  In the case of auxiliary light using a xenon tube, although the color temperature of the auxiliary light can be changed somewhat depending on the gas pressure of the xenon gas and the charging voltage of the capacitor, it is basically determined by the physical characteristics of the xenon gas. The color temperature cannot be changed greatly from around 6000 ° K.

Therefore, if the subject is relatively close and the auxiliary light can dominate the outside light, the distance can be within the same angle of view even though the subject can be white balanced. However, there is a problem that white balance cannot be achieved when there is a subject whose external light is dominant even when the auxiliary light is irradiated far away. For example, when shooting a nearby person in a room with a fluorescent light source depth, if the xenon tube's auxiliary light color is bluish and the fluorescence is yellowish green, the xenon tube color for the nearby person When the white balance is achieved by the temperature, the background in which the auxiliary light is low with respect to the illuminance of the fluorescent lamp becomes more yellow, which may result in an unnatural color as an overall image.
JP-A-8-140104 Japanese Patent Laid-Open No. 7-301842 Japanese Patent Publication No.8-17498 JP 2002-116481 A

  In Patent Document 4, a means for controlling the ratio of light emission amounts of R, G, and B LEDs and a color temperature sensor are provided so that the color temperature of the object scene detected by the color temperature sensor is obtained. A camera for controlling the light emission amount of each LED is disclosed. By performing such adjustment, it is possible to obtain an image that does not feel uncomfortable as a whole by matching the colors of the subject and the background.

  On the other hand, as shown in FIG. 2, even when the same amount of forward current is supplied to the LEDs of R, G, and B colors, the obtained luminous intensity is different. In general, if the LEDs have the same chip size, the luminance of G is high when the current is small, followed by R and then B. However, when the current is increased, R> G> B, and R can output the maximum luminance. Therefore, it is possible to prioritize the reach distance by maximizing the amount of auxiliary light regardless of the color temperature of the external light. By doing so, the necessary illuminance can be obtained with less energy than that of Patent Document 4 at a distance where the auxiliary light can sufficiently reach.

  In addition, some image pickup devices using a strobe used in a camera change the white balance gain in accordance with the distance of the object field. There is no white balance gain circuit that changes the color balance of the illumination light itself.

  In view of the above points, the present invention makes it possible to selectively use image quality priority or luminance priority depending on the distance distribution of the object within the angle of view and the object brightness, and obtain a good image quality with less energy depending on the scene. An object of the present invention is to provide an imaging device capable of performing the above.

  An imaging apparatus according to a first aspect of the present invention includes R, G, B3 color light emitting diodes used as an illumination light source, illumination means for adjusting the luminance of each of the light emitting diodes, and a plurality of regions within an angle of view. A distance measuring means for measuring a distance, a color temperature measuring means for measuring the color temperature of a subject, a luminance measuring means for measuring the luminance of a plurality of areas within an angle of view, and a distance distribution of the subject, subject brightness and color temperature. And a main control means for adjusting the color temperature of the illumination means by controlling the driving of the light emitting diodes of the three colors.

  According to a second aspect of the present invention, in the imaging apparatus according to the first aspect, the main control means is bright within an angle of view with respect to the illuminance of the illuminating means or cannot obtain an appropriate output even when illuminated. The distance that can reduce the luminance difference between the area including one or both of the conditions and the far side by irradiating the illumination means and obtain a good output image. In the case of a subject including an area determined to be in the area, the luminance of the light emitting diodes of the three colors is controlled so as to be the color temperature of the far side area.

  According to a third aspect of the present invention, in the imaging apparatus according to the first aspect, the main control means can obtain an appropriate output value by illuminating the entire angle of view with the illumination means with a narrow distance distribution within the angle of view. The light emitting diodes of three colors are driven so as to give priority to the luminance of the illuminating means when the distance and the luminance are possible.

  According to a fourth aspect of the present invention, in the imaging apparatus according to the first aspect, the main control means obtains an appropriate output value even if the distance distribution in the angle of view is narrow and the entire illumination angle is not illuminated by the illumination means. The light emitting diodes of three colors are driven so that the colors are opposite to the colors of the external light source when the distance and the brightness are within the range.

  According to a fifth aspect of the present invention, there is provided a digital still camera including the image pickup apparatus according to any one of the first to fourth aspects.

  According to a sixth aspect of the present invention, there is provided an imaging method in which R, G, and B three-color light emitting diodes are used as illumination light sources, distance measurement of a plurality of areas within an angle of view, measurement of a subject color temperature, It measures the luminance of a plurality of areas in the corner and controls the luminance of each light emitting diode according to the distance distribution, luminance and color temperature of the subject.

  According to a seventh aspect of the present invention, in the imaging method according to the sixth aspect of the present invention, either the distance within the angle of view is bright with respect to the illuminance of the illuminating means, or a distance where an appropriate output cannot be obtained even when illuminated. Alternatively, it is determined that the area including both conditions and the distance is low enough to obtain a good output image by reducing the luminance difference between the area and the far side by illuminating the illumination means. In the case of a subject including a region, the luminance of the light emitting diodes of the three colors is controlled so that the color temperature of the far region is the same.

  The invention according to claim 8 is the imaging method according to claim 6, wherein the distance distribution within the angle of view is narrow and the distance and brightness at which a proper output value can be obtained by illuminating the entire angle of view with illumination means. In some cases, the three color light emitting diodes are driven so as to give priority to the luminance of the illumination means.

  According to a ninth aspect of the present invention, in the imaging method according to the sixth aspect, the distance distribution within the angle of view is narrow, and the distance and brightness can obtain an appropriate output value without illuminating the entire angle of view with the illumination means. In some cases, the three-color light emitting diodes are driven so as to be opposite to the color of the external light source.

  According to the present invention, since the color temperature of the illuminating unit is adjusted by controlling the driving of the three color light emitting diodes according to the distance distribution of the subject, the luminance of the subject, and the color temperature, the illuminating unit can be driven efficiently. it can. For this reason, it is possible to reduce the power consumption of a device such as a digital still camera incorporating the imaging device.

  FIG. 1 shows a circuit diagram in an embodiment of the present invention. This circuit diagram is used for a digital still camera in which the imaging apparatus of this embodiment is incorporated. As shown in FIG. 1, it has R-LED1a, G-LED1b, and B-LED1c used as an illumination light source, and the system controller 10 as a main control means which controls the whole.

  The R-LED 1a, G-LED 1b, and B-LED 1c are supplied with power through the power source 2, the power source circuit 3, and the booster circuit 4. The LEDs 1a, 1b, and 1c have operational amplifiers 5a, 5b, and 5c, respectively. The operational amplifiers 5a, 5b, and 5c are connected to the DA converter 11 in the system controller 10, and current is supplied by the output of the DA converter 11. Is done.

  The system controller 10 includes the above-described DA converter 11, DMA circuit 12, image processing unit 13, compression processing unit 14, and memory controller 15, which are driven by control from the CPU 16. The CPU 16 accesses the ROM 17 and signals. The ROM 17 stores a program 17a for controlling the entire image pickup apparatus, an amount of current to be supplied to the three color LEDs 1a, 1b, and 1c, and luminance data generated by the LEDs 1a, 1b, and 1c when the current is supplied. A table 17b is stored.

  The DMA circuit 12 of the system controller 10 accesses the SDRAM 18 serving as a work area during operation of the imaging apparatus. The memory card controller 15 outputs an image signal to the memory card 19 which is an external memory. As a result, the captured image is recorded in the memory card 19.

  In the digital still camera, the light that has passed through the photographing lens 21 is imaged on the CCD 22 to photograph the subject. The CCD 22 is driven by a drive circuit 23 connected to the CPU 16 of the system controller 10. The signal from the CCD 22 is processed by the signal processing circuit 24 and then introduced into the image processing unit 13 via the agc circuit 25 and the AD converter 26, and the image processing unit 13 performs image processing. The image-processed signal is output to the memory card 19 via the memory card controller 15 described above.

  In this embodiment, distance measuring means for measuring the distance of a plurality of points within the angle of view, luminance measuring means for measuring the brightness of the point corresponding to the distance measuring point of the distance measuring means, and distance measuring by the distance measuring means Color temperature measuring means for measuring the color temperature of the point corresponding to the point. As the distance measuring means, an AF sensor 28 connected to the CPU 16 is used. The AF sensor 28 has a function of automatically measuring the absolute distance from the subject. The color temperature measurement unit and the luminance measurement unit are provided in the image processing unit 13 in the system controller 10 and measure the color temperature and the luminance by performing integration for each of R, G, and B colors.

  Next, control of each color LED 1a, 1b, 1c based on the results measured by the distance measuring means, the luminance measuring means, and the color temperature measuring means will be described for each pattern. This control is performed by the system controller 10 as main control means.

(Pattern 1)
Distance distribution = Wide distance distribution within the angle of view, the near subject is a distance that the light from the LED can reach sufficiently, and the far side is a distance where the external light is dominant even if the light from the LED reaches Subject brightness = The subject brightness on the far side is greater than the brightness of the near subject. Color temperature = The color temperature on the near side differs from the color temperature on the far side.

  The light emission of the LEDs 1a, 1b, and 1c in the above pattern 1 turns on the LEDs so that the color temperature is on the far side. Thereby, the color temperature difference with the part where LED as an illumination light source cannot become dominant can be eliminated. Therefore, the difference in luminance between the near side and the far side can be reduced, and both can express gradation, and both the near side and the far side have the same hue, so that the image quality is improved.

(Pattern 2)
Distance distribution = Distance where the distance distribution within the angle of view is narrow and the light from the LED can reach the subject on the far side sufficiently. Subject luminance = Luminance for which an appropriate signal amount cannot be obtained without illuminating the LED Color temperature = This The pattern does not require color temperature data.

  The light emission of the LEDs 1a, 1b, and 1c in the above pattern 2 is performed by turning on the LEDs 1a, 1b, and 1c of the respective colors so that the necessary luminance can be obtained with the minimum energy amount. For example, up to 1000 mcd, only the R-LED 1a is turned on, then the G-LED 1b is turned on, and when the brightness of about 1500 mcd or more is required, the B-LED 1c is further turned on. The white balance is set by the white balance control unit in the image processing unit 13 in the system controller 10. Such control can improve battery life.

(Pattern 3)
Distance distribution = Distance where the distance distribution within the angle of view is narrow and the light from the LED can reach the far side subject sufficiently. Subject brightness = Brightness that can obtain the appropriate signal amount without irradiating the LED Color Temperature = e.g. R: G: B = 2: 4: 1 color temperature

  The light emission of the LEDs 1a, 1b, and 1c in the above pattern 3 is white balance by turning on the LEDs 1a, 1b, and 1c of each color at a ratio of R: G: B = 2: 1: 4. In such control, the color temperature of the input signal can be adjusted by the illumination light from the LEDs 1a, 1b, 1c. At this time, generally, the white balance is digitally gained after quantization, but the quantization error generated at this time can be reduced, and the image quality is improved.

  As described above, in this embodiment, since the subject pattern is segmented based on the subject distance, brightness, and color temperature information, the image quality can be improved and the battery life can be extended.

  As described above, in the present embodiment, the background color cannot be made close to the near-side subject even if the maximum illumination intensity output from the illumination unit is irradiated from the distance distribution within the angle of view and the subject brightness. In the case where the condition is determined, the illumination unit is irradiated in accordance with the hue of the background color, so that the hue of the entire screen is made uncomfortable and an image can be taken.

  Also, in the condition that the background color can be made close to the front subject within the maximum illuminance range output by the illumination means from the distance distribution within the angle of view and subject brightness, the least energy Thus, the necessary illuminance can be obtained, and the color of the entire screen can be taken without any sense of incongruity.

  Furthermore, by adjusting the color of the illumination means so as to reduce the amount of white balance gain required in the subsequent circuit from the distance distribution within the angle of view and subject brightness, there is less random noise and quantization noise. A good image can be taken.

  In a digital still camera incorporating such an imaging device, compared to a digital still camera equipped with a conventional xenon tube, depending on the scene, the color in the screen can be improved, and an image with less noise can be obtained. Alternatively, since the required luminance can be given to the subject with a small amount of energy, the battery life can be improved.

It is a circuit diagram of one embodiment of the present invention. It is a characteristic view which shows the light emission characteristic of each color LED of R, G, B.

Explanation of symbols

1a, 1b, 1c LED
2 power supply 3 power supply circuit 10 system controller 13 image processing unit 14 compression circuit 16 CPU
17 ROM
21 Shooting lens 22 CCD
29 AF sensor

Claims (9)

  R, G and B light emitting diodes used as an illumination light source, illumination means for adjusting the luminance of each light emitting diode, distance measuring means for measuring a plurality of areas within the angle of view, and subject color Color temperature measuring means for measuring temperature, luminance measuring means for measuring the luminance of a plurality of regions within the angle of view, and driving of the three color light emitting diodes are controlled according to the distance distribution of the subject, the subject luminance and the color temperature. An image pickup apparatus comprising: main control means for adjusting the color temperature of the illumination means.   The main control means includes an area including either or both of a condition that is bright within the angle of view with respect to the illuminance of the illumination means, or a distance at which an appropriate output cannot be obtained even when illuminated. When the subject includes a region that is judged to be at a distance where a good output image can be obtained by lowering the luminance difference from the far side by illuminating the illumination means with respect to the far side, The imaging apparatus according to claim 1, wherein the luminance of the light emitting diodes of the three colors is controlled so that the color temperature of the region is obtained.   The main control means gives priority to the brightness of the illumination means when the distance distribution within the angle of view is narrow and the distance and brightness can obtain an appropriate output value by illuminating the entire angle of view with the illumination means. The image pickup apparatus according to claim 1, wherein three color light emitting diodes are driven.   The main control means is opposed to the color of the external light source when the distance distribution within the angle of view is narrow and the distance and brightness can obtain an appropriate output value without illuminating the entire angle of view with the illumination means. The image pickup apparatus according to claim 1, wherein the light emitting diodes of three colors are driven so as to obtain a color to be displayed.   A digital still camera comprising the imaging device according to claim 1. In an imaging method using light emitting diodes of R, G and B colors as illumination light sources,
Ranging multiple areas within the field of view, measuring the color temperature of the subject, and measuring the brightness of the multiple areas within the field of view, depending on the distance distribution, luminance, and color temperature of the subject, An imaging method characterized by controlling luminance.   An area that includes either or both of the conditions that are brighter than the illuminance of the illumination means within the angle of view, or a distance that cannot provide an appropriate output even when illuminated, and the brightness is low for this area In addition, the color temperature of the far side region is obtained when the subject includes a region that is judged to be at a distance where a good output image can be obtained by reducing the luminance difference from the far side by illuminating the illumination means. The imaging method according to claim 6, wherein the brightness of the light emitting diodes of the three colors is controlled as described above.   When the distance distribution within the angle of view is narrow and the distance and luminance can obtain an appropriate output value by illuminating the entire angle of view with the illumination means, the three color light emitting diodes are set so that the luminance of the illumination means is given priority. The imaging method according to claim 6, wherein the imaging method is driven.   The distance distribution within the angle of view is so narrow that the appropriate output value can be obtained without illuminating the entire angle of view with the illumination means, so that the color is opposite to the color of the external light source. The imaging method according to claim 6, wherein a color light emitting diode is driven.

Images