JP4889225B2 - Electronic camera - Google Patents

Description

  The present invention relates to an electronic camera, and more particularly to an electronic camera that adjusts the white balance of a captured scene image, for example.

  An example of a conventional electronic camera of this type is disclosed in Patent Document 1. According to this prior art, when the fluorescent lamp manual mode is selected, the color measurement result R / B obtained by the color measurement unit is compared with each of the threshold values K1 and K2.

  If K1 <R / G, the light source is considered to be a light bulb color fluorescent lamp, and the gain corresponding to the light bulb color is selected for white balance adjustment. If K2 <R / G ≦ K1, the light source is regarded as a white fluorescent lamp, and a gain corresponding to white is selected for white balance adjustment.

If K3 <R / G ≦ K2, the light source is regarded as a day white fluorescent lamp, and a gain corresponding to day white is selected for white balance adjustment. If none of the above conditions is met, the light source is considered to be a daylight color fluorescent lamp, and the gain corresponding to the daylight color is selected for white balance adjustment.
JP-A-6-165189 [H04N9 / 04, 9/73]

  However, in the prior art, when shooting an object scene irradiated with a plurality of light sources, there is a possibility that the color of the photographed image greatly fluctuates due to a slight change in the object scene. For example, when each of the persons A and B is photographed in a state where both the bulb-color fluorescent lamp and the white fluorescent lamp are irradiated, if the measurement result R / G fluctuates in the vicinity of the threshold value K1, the selected gain greatly changes. To do. As a result, the hue between the photographed image of the person A and the photographed image of the person B is greatly different.

    Therefore, a main object of the present invention is to provide an electronic camera capable of accurately and stably adjusting the hue of a captured image.

The electronic camera according to the invention of claim 1 is a photographing means (22) for outputting color information signals of a plurality of colors representing an object scene, an amplifying means (24a, 24b) for amplifying the color information signals output from the photographing means, Discriminating whether or not the adjustment gain for obtaining a predetermined white balance for the color information signal output from the amplifying means belongs to a specific range defined by a plurality of numerical values respectively corresponding to a plurality of different specific light source colors Means (S21), a first setting means (S23) for setting the adjustment gain in the amplifying means when the discrimination result of the discrimination means is affirmative, and the specified range when the discrimination result of the discrimination means is negative A second setting that sets a predetermined gain belonging to one of a plurality of predetermined ranges respectively corresponding to the plurality of different specific light source colors to the amplifying means according to a magnitude relationship between the plurality of numerical values to be adjusted and the adjustment gain Means (S25, S 27, S29, S31, S33, S35, S37).

The photographing unit outputs color information signals of a plurality of colors representing the object scene. The output color information signal is amplified by the amplification means. The discriminating unit discriminates whether or not an adjustment gain for obtaining a predetermined white balance for the color information signal output from the amplifying unit belongs to a specific range. Here, the specific range is a range defined by a plurality of numerical values respectively corresponding to a plurality of different specific light source colors. If the determination result of the determination means is affirmative, the adjustment gain described above is set to the amplification means by the first setting means. If the determination result of the determining means is negative, a plurality of predetermined ranges corresponding respectively to the plurality of different specific light source colors according to the magnitude relationship between the plurality of numerical values defining the specific range and the adjustment gain . A predetermined gain belonging to one of them is set in the amplification means by the second setting means.

The specific range has a spread defined by a plurality of numerical values. When the adjustment gain that provides a predetermined white balance belongs to this specific range, this adjustment gain is effective. On the other hand, when the adjustment gain that provides a predetermined color balance does not belong to the specific range, the plurality of different specific light source colors according to the magnitude relationship between the numerical values defining the specific range and the adjustment gain A predetermined gain belonging to one of a plurality of predetermined ranges respectively corresponding to is effective. That is, the gain to be effective has a value related to a specific range having a certain spread. As a result, the color tone of the photographed image can be adjusted accurately and stably.

  The electronic camera according to the invention of claim 2 is dependent on claim 1, and further comprises a determining means (S19) for determining an adjustment gain based on the color information signals of a plurality of colors amplified by the amplifying means. The value of the adjustment gain determined by the means is compared with each of a plurality of numerical values.

  The electronic camera according to the invention of claim 3 is dependent on claim 1 or 2, and the second setting means selects one of a plurality of gains respectively corresponding to a plurality of different light source colors as a predetermined gain.

An electronic camera according to a fourth aspect of the invention is dependent on any one of the first to third aspects, and the specific range corresponds to a daylight white light source.

According to the present invention, the specific range has a spread defined by a plurality of numerical values. When the adjustment gain that provides a predetermined white balance belongs to this specific range, this adjustment gain is effective. On the other hand, when the adjustment gain that provides a predetermined color balance does not belong to the specific range, the plurality of different specific light source colors according to the magnitude relationship between the numerical values defining the specific range and the adjustment gain A predetermined gain belonging to one of a plurality of predetermined ranges respectively corresponding to is effective. That is, the gain to be effective has a value related to a specific range having a certain spread. As a result, the color tone of the photographed image can be adjusted accurately and stably.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

  Referring to FIG. 1, a digital camera (electronic camera) 10 of this embodiment includes an optical lens 12. The optical image of the object scene is irradiated onto the imaging surface of the image sensor 16 forming the imaging device 22 via the optical lens 12. The imaging surface is covered with a primary color filter 14 having the Bayer arrangement shown in FIG. For this reason, the amount of electric charge generated in each of the plurality of light receiving elements formed on the imaging surface reflects the light quantity of R (Red), G (Green), or B (Blue).

  A TG (Timing Generator) 42 gives a plurality of timing signals to the image sensor 16 in response to a vertical synchronization signal Vsync generated every 1/30 seconds. The charge generated by each of the plurality of light receiving elements, that is, the pixel signal is read from the image sensor 16 in a raster scanning manner in response to the timing signal. The read pixel signal is converted into pixel data which is a digital signal by the A / D converter 18, and the converted pixel data is subjected to a series of correlated double sampling, automatic gain adjustment and color separation by the preprocessing circuit 20. Processed. By color separation, all color information of R, G, and B is assigned to each pixel. The R data, G data, and B data assigned to the same pixel are simultaneously output to the white balance adjustment circuit 26.

  The R data is subjected to amplification processing according to the gain Gr by the amplifier 24a, and is then supplied to the matrix operation circuit 30 and the integration circuit 28r. The B data is subjected to amplification processing according to the gain Gb by the amplifier 24b, and is then supplied to the matrix operation circuit 30 and the integration circuit 28b. The G data is directly supplied to the matrix operation circuit 30 and the integration circuit 28g.

  The matrix operation circuit 30 generates YUV data based on the given RGB data. The post-processing circuit 32 converts the generated YUV data into a composite video signal, and outputs the converted composite video signal to the LCD monitor 34. As a result, a real-time moving image (through image) of the object scene is displayed on the monitor screen.

  Each of the integration circuits 28r, 28g, and 28b performs integration processing in the manner described below. Referring to FIG. 7, the object scene is divided into 16 parts in each of the horizontal direction and the vertical direction. As a result, 256 divided areas are allocated on the object scene. The integrating circuit 28r integrates R data for each divided area, the integrating circuit 28g integrates G data for each divided area, and the integrating circuit 28b integrates B data for each divided area. As a result, the integrated values Rij, Gij and Bij of each divided area are generated by spending one frame period (= 1/30 second).

  Note that i is the position number of the divided area in the horizontal direction, and indicates any value from “1” to “16”. Similarly, j is the position number of the divided area in the vertical direction, and indicates any value from “1” to “16”.

  When the fluorescent lamp mode is selected by the mode SW 38, the CPU 36 executes a white balance adjustment process according to the flowcharts shown in FIGS. 3 to 4 every time the vertical synchronization signal Vsync is generated. The control program corresponding to this flowchart is stored in the flash memory 40.

  First, in step S1, gains Gr and Gb are set to initial values, and variables i and j and variables ΣR, ΣG, and ΣB described later are set to “0”.

  In step S3, divided areas specified by variables i and j out of integrated values Rij, Gij and Bij based on R data, G data and B data subjected to white balance adjustment according to gains Gr and Gb indicating initial values. The integrated values Rij, Gij and Bij are taken in.

  In step S5, Yij, (R−G) ij and (B−G) ij are calculated based on the integrated values Rij, Gij and Bij fetched. Yij corresponds to an integrated value of Y data detected from the divided area (i, j), and can be defined as “luminance evaluation value”. On the other hand, (R−G) ij is a difference value between the integrated values Rij and Gij, and (B−G) ij is a difference value between the integrated values Bij and Gij.

In the subsequent step S7, fy (RG) ij and fy (BG) ij are obtained according to Equation 1.
[Equation 1]
fy (RG) ij = (RG) ij / c1 * Yij
fy (BG) ij = (BG) ij / c2 * Yij
c1, c2: Constant The difference values (R−G) ij and (B−G) ij obtained in step S5 reflect the exposure amount at the time of pre-exposure. That is, the numerical value increases as the exposure amount increases, but decreases as the exposure amount decreases. If the difference values (R−G) ij and (B−G) ij having such characteristics are defined as “color evaluation values” of the divided area of interest, the color evaluation values vary depending on the exposure amount.

  On the other hand, the color of the object scene does not inherently depend on the exposure amount, and the object field color is always the same unless the subject and the light source are changed. Therefore, even if the exposure amount is changed, the color evaluation value should continue to take the same value.

  Therefore, in this embodiment, the difference values (R−G) ij and (B−G) ij are respectively divided by numerical values “c1 * Yij” and “c2 * Yij” related to the exposure amount. The fy (RG) ij and fy (BG) ij obtained in this way are defined as “color evaluation values”.

  In step S9, it is determined where the color evaluation values fy (RG) ij and fy (BG) ij are located in the color distribution chart shown in FIG. 5B, and a weight corresponding to the determined position. The coefficient Wij is detected from the table 40t created in the manner shown in FIG. The table 40t is stored in the flash memory 40. In subsequent step S11, the detected weighting coefficient Wij is multiplied by each of the integrated values Rij, Gij and Bij fetched in step S3 to obtain weighted values Rij * Wij, Gij * Wij and Bij * Wij.

  According to FIG. 5A, the weighting coefficient Wij indicates any value of “0”, “6”, “7”, and “8”. Among these, the areas to which “6”, “7”, and “8” are assigned correspond to the pull-in range. The divided area in which the color evaluation value outside the pull-in range is detected is invalidated by the process of step S11.

  In the object scene shown in FIG. 6, the table TBL is arranged in a room that can enter and exit from the door DR, the persons M1 and M2 exist around the table TBL, and the vase VS is placed on the table TBL. Here, when the color evaluation values obtained in the divided areas covering each of the table TBL and the vase VS are out of the pull-in range, and the color evaluation values obtained in the remaining divided areas belong to the pull-in range, hatched lines in FIG. The 56 divided areas shown are invalid areas, and the other 200 divided areas are valid areas.

In step S13, the weighted values Rij * Wij, Gij * Wij and Bij * Wij calculated in step S11 are integrated for each color information. Specifically, the calculation according to Equation 2 is executed, and the currently calculated weight values Rij * Wij, Gij * Wij and Bij * Wij are added to the current variables ΣR, ΣG and ΣB.
[Equation 2]
ΣR = ΣR + Rij * Wij
ΣG = ΣG + Gij * Wij
ΣB = ΣB + Bij * Wij
In step S15, it is determined whether the integration according to Equation 2 has been repeated 256 times. If NO, the count value i or j is updated in step S17, and the process returns to step S3. As a result, the processing of steps S3 to S13 is executed for the integrated values Rij, Gij and Bij obtained in each of the 256 divided areas shown in FIG.

When YES is determined in step S15, the variable ΣR indicates the sum of the weight values Rij * Wij, the variable ΣG indicates the sum of the weight values Gij * Wij, and the variable ΣB indicates the sum of the weight values Bij * Wij. . In step S19, the total values ΣR, ΣG and ΣB thus obtained are subjected to the calculation shown in Equation 3 to calculate the divided values α1 and β1.
[Equation 3]
α1 = k1 * ΣG / ΣR
β1 = k2 * ΣG / ΣB
k1, k2: Constant In step S21, it is determined whether or not the calculated division values α1 and β1 satisfy both of the two conditions shown in Equation 4.
[Equation 4]
THr1 <α1 ≦ THr2
THb1 <β1 ≦ THb2
The condition is satisfied if the divided value α1 is greater than the threshold value THr1 and less than or equal to the threshold value THr2, and if the divided value β1 is greater than the threshold value THb1 and less than or equal to the threshold value THb2. If the condition is satisfied, the process proceeds to step S23, where the gain Gr indicating the division value α1 is set in the amplifier 24a, and the gain Gb indicating the division value β1 is set in the amplifier 24b.

  If the condition shown in Equation 4 is not satisfied, it is determined in step S25 whether or not the division value β1 exceeds the threshold value THb2. If “YES” here, the process proceeds to a step S27 to set the gain Gr indicating the predetermined value α2 in the amplifier 24a and set the gain Gb indicating the predetermined value β2 in the amplifier 24b.

  If “NO” in the step S25, it is determined whether or not the division value β1 is equal to or less than the threshold value THb1 in a step S29. If “YES” here, the process proceeds to a step S31, the gain Gr indicating the predetermined value α3 is set in the amplifier 24a, and the gain Gb indicating the predetermined value β3 is set in the amplifier 24b.

  If “NO” in the step S29, it is determined whether or not the division value α1 exceeds the threshold value THr2. If “YES” here, the process proceeds to a step S35, the gain Gr indicating the predetermined value α4 is set in the amplifier 24a, and the gain Gb indicating the predetermined value β4 is set in the amplifier 24b. If “NO” in the step S33, the process proceeds to a step S37, the gain Gr indicating the predetermined value α5 is set in the amplifier 24a, and the gain Gb indicating the predetermined value β5 is set in the amplifier 24b.

  Referring to FIG. 8, threshold values THr1 and THr2 are located on the horizontal axis defining gain Gr, and threshold values THb1 and THb2 are located on the vertical axis defining gain Br. The daylight white area surrounded by the thresholds THr1, THr2, THb1, and THb2 is an area where accurate white balance adjustment can be performed when a daylight white fluorescent lamp is used as a light source.

  When the divided values α1 and β1 belong to the daylight white area, the divided values α1 and β1 are set as the gains Gr and Gb. When the divided values α1 and β1 deviate from the daylight white area, one of the predetermined values α2 to α5 is set as the gain Gr according to the position specified by the divided values α1 and β1, and the predetermined values β2 to β5 Either one is set as the gain Gb. The white balance is adjusted by the gains Gr and Gb set in this way.

  Here, the predetermined values α2 and β2 are gains suitable for white fluorescent lamps, and the predetermined values α3 and β3 are gains suitable for three-wavelength daylight fluorescent lamps. The predetermined values α4 and β4 are gains suitable for daylight fluorescent lamps, and the predetermined values α5 and β5 are gains suitable for three-wavelength daylight white fluorescent lamps. All of these gains indicate values on the periphery of the daylight white area.

  As can be seen from the above description, the imaging device 22 outputs RGB data representing the object scene. Of the output RGB data, R data and B data are respectively amplified by the amplifiers 24 a and 24 b forming the white balance adjustment circuit 26. The CPU 36 calculates gains α1 and β1 (adjustment gain) for obtaining a predetermined white balance for the RGB data output from the white balance adjustment circuit 26, and the calculated gains α1 and β1 are in the daylight white area (specific range). It is determined whether or not it belongs (S21). If the determination result is affirmative, the gains α1 and β1 are set in the amplifiers 24a and 24b, respectively (S23). If the determination result is negative, gains α2 (α3, α4, α5) and β2 (β3, β4, β5) indicating values on the periphery of the daylight white area are set in the amplifiers 24a and 24b, respectively.

  Thus, when the gains α1 and β1 belong to the daylight white area, the gains α1 and β1 are effective. On the other hand, when the gains α1 and β1 do not belong to the daylight white area, the gains α2 (α3, α4, α5) and β2 (β3, β4, β5) indicating values on the periphery of the daylight white area are effective. In other words, the gain to be enabled always belongs to the daylight white area.

  As a result, an abrupt change in gain due to a slight change in the object scene is prevented, and the hue of the captured image can be adjusted accurately and stably. Such an effect is prominent when the object scene is photographed under a plurality of light sources having different colors.

  In this embodiment, numerical values on the periphery of the daylight white area are assigned as gains α2 (α3, α4, α5) and β2 (β3, β4, β5). However, as long as there is no sudden change in gain that can be visually recognized, numerical values that deviate from the daylight white area are set as gains α2 (α3, α4, α5) and β2 (β3, β4, β5) as shown in FIG. May be. In FIG. 9, the range surrounded by the solid line and the dotted line is a range where there is no sudden change in gain that can be visually recognized.

  Furthermore, numerical values inside the peripheral edge of the daylight white area may be set as gains α2 (α3, α4, α5) and β2 (β3, β4, β5).

It is a block diagram which shows the structure of one Example of this invention. It is an illustration figure which shows an example of the primary color filter applied to the FIG. 1 Example. It is a flowchart which shows a part of operation | movement of CPU applied to the FIG. 1 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 1 Example. (A) is an illustration figure which shows an example of the weighting coefficient allocated to the table, (B) is the color distribution state on the plane prescribed | regulated by the BG axis | shaft and the RG axis | shaft, and the allocation state of the drawing-in range. It is an illustration figure shown. It is an illustration figure which shows an example of an object scene. It is an illustration figure which shows an example of the allocation state of several division area. It is an illustration figure which shows a part of white balance adjustment operation | movement. It is an illustration figure which shows a part of operation | movement of the other Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Digital camera 16 ... Image sensor 22 ... White balance adjustment circuit 24a, 24b ... Amplifier 28r, 28g, 28b ... Integration circuit 30 ... CPU
42: Flash memory

Claims (4)

Photographing means for outputting color information signals of a plurality of colors representing an object scene;
Amplifying means for amplifying the color information signal output from the photographing means;
It is determined whether or not the adjustment gain for obtaining a predetermined white balance for the color information signal output from the amplifying means belongs to a specific range defined by a plurality of numerical values respectively corresponding to a plurality of different specific light source colors. Discrimination means,
A first setting unit that sets the adjustment gain in the amplification unit when the determination result of the determination unit is positive; and a plurality of numerical values that define the specific range when the determination result of the determination unit is negative And a second setting means for setting a predetermined gain belonging to one of a plurality of predetermined ranges respectively corresponding to the plurality of different specific light source colors in the amplification means according to a magnitude relationship between the adjustment gain and the adjustment gain. , Electronic camera. Determining means for determining the adjustment gain based on a plurality of color information signals amplified by the amplifying means;
The electronic camera according to claim 1, wherein the determination unit compares the value of the adjustment gain determined by the determination unit with each of the plurality of numerical values.   The electronic camera according to claim 1, wherein the second setting unit selects one of a plurality of gains respectively corresponding to the plurality of different light source colors as the predetermined gain.   The electronic camera according to claim 1, wherein the specific range corresponds to a daylight white light source.

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