JP4887582B2 - Image processing device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image processing apparatus that generates a luminance signal from RGB signals.
[0002]
[Prior art]
Conventionally, when a luminance signal is generated from an RGB signal, each of R (red), G (green), and B (blue) is multiplied and added by a certain coefficient. For example, in the case of NTSC, the luminance signal Y is obtained by Y = 0.3 × R + 0.59 × G + 0.11 × B.
[0003]
FIG. 4 is a block diagram showing a configuration of a conventional image processing apparatus. The image processing apparatus shown in the figure shows a configuration of a portion that receives three primary color signals (R, G, B) from an imaging means such as a camera device and outputs a luminance signal Y. Here, 40, 41, and 42 are multipliers for adjusting the levels of the R, G, and B signals in order to correct the white balance of the subject, and 43, 44, and 45 are R, G that have undergone white balance correction. Γ (gamma) means for nonlinearly processing the B signal, 46 is a coefficient by which R is multiplied when generating the luminance signal Y, 47 is a coefficient by which G is multiplied when generating the luminance signal Y, 48 Is a coefficient to be multiplied by B when generating the luminance signal Y, and 49 is an adder for adding R, G, B multiplied by the coefficient when generating the luminance signal Y.
[0004]
In general, white balance correction is performed by setting the gain of the G signal to 1 and adjusting the gains of the other R and B signals. Further, when obtaining color difference signals from R, G, B signals (Rγ, Gγ, Bγ signals), a separate matrix circuit for color difference signals is provided, but this is omitted because it is not directly related to the present invention.
[0005]
[Problems to be solved by the invention]
In this conventional image processing apparatus, when the white balance gain of the R signal or B signal increases, the S / N (signal-to-noise ratio) of the R and B signals deteriorates, so that they are generated from R, G, and B. The S / N of the luminance signal also deteriorates, and there is a problem that the image quality deteriorates.
[0006]
An object of the present invention is to provide an image processing apparatus in which the S / N of a luminance signal does not deteriorate even when the white balance gain is increased.
[0007]
[Means for Solving the Problems]
In order to solve this problem, the present invention provides a first image processing apparatus for processing a plurality of color information signals, wherein the signal levels of each of the plurality of color information signals are independently adjusted in order to adjust the white balance of the subject. Adjusting means, γ means for nonlinearly processing a plurality of color information signals level-adjusted by the first adjusting means, and second adjustment for independently adjusting the signal levels of the plurality of color information signals subjected to nonlinear processing Means, a combining means for combining a plurality of color information signals level-adjusted by the second adjusting means and outputting them as luminance signals, and a plurality of the second adjusting means depending on the adjustment amount in the first adjusting means. Control means for controlling the adjustment amount of each color information signal.
[0008]
As a result, the synthesis ratio for synthesizing the luminance signal is adjusted according to the adjustment amount for adjusting the white balance, so that the S / N deterioration of the luminance signal can be suppressed.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to Embodiment 1 of the present invention. In FIG. 1, 10, 11, and 12 are multipliers, 13, 14, and 15 are γ (gamma) means, 16, 17, and 18 are multipliers, 19 is an adder, and 110 is a multiplier. It is a control means which controls the coefficient given to the units 16-18.
[0011]
The operation of the image processing apparatus configured as described above will be described below.
[0012]
For example, in an imaging apparatus, a captured subject image is converted into R, G, and B signals as a plurality of color information signals, and then input to the image processing apparatus in the present embodiment. In this embodiment, for white balance correction, the multipliers 10 to 12 multiply the R, G, and B signals by the white balance gains Rwbg, Gwbg, and Bwbg, and output the signals as Rwb, Gwb, and Bwb. Gamma means 13-15 performs non-linear processing, outputs as Rγ, Gγ, Bγ, multipliers 16-18 multiply coefficients kr, kg, kb by Rγ, Gγ, Bγ, and adder 19 produces kr, kg, kb. Rγ, Gγ, and Bγ multiplied by are added together and output as a luminance signal Y. When this is expressed by a mathematical formula, Y = kr × Rγ + kg × Gγ + kb · Bγ.
[0013]
The control means 110 changes the coefficients kr, kg, kb for generating the luminance signal Y according to the white balance gains Rwbg, Gwbg, Bwbg.
[0014]
FIG. 2 is a schematic diagram for explaining the operation of the control unit 110 in the first embodiment. FIG. 2A shows the characteristic of the coefficient kr with respect to the white balance gain Bwbg multiplied by the B signal of the control unit 110. As shown in the figure, kr holds the value r1 when Bwbg is from 0 to rst, interpolates between value r1 and value r2 when Bwbg is from rst to red, and holds value r2 when Bwbg is greater than or equal to red FIG. 2B shows the characteristic of the coefficient kg with respect to the white balance gain Bwbg of the control means 110. kg holds the value g1 when Bwbg is 0 to gst, and Bwbg is ged from gst. Up to the value obtained by interpolating between the value g1 and the value g2, the value g2 is held when Bwbg is ged or more. FIG. 2C shows the characteristic of the coefficient kb with respect to the white balance gain Bwbg of the control means 110. Kb holds the value r1 when Bwbg is from 0 to bst, and Bwbg is from bst to be Up to d, the value is interpolated between the value b1 and the value b2, and when Bwbg is not less than bed, the value b2 is held, and the r1, r2, g1, g2, b1, b2 are r1 <r2, g1> The relationship is g2, b1> b2.
[0015]
In the image processing apparatus configured as described above, as the white balance gain Bwbg for the B signal increases, the coefficient kr multiplied by the Rγ signal increases, and the coefficient kb multiplied by the Bγ signal decreases, so the white balance gain Bwbg increases. Even if the S / N of the Bγ signal is deteriorated, the luminance signal Y in the above formula can reduce the ratio of the Bγ signal and increase the ratio of the Rγ signal to suppress the S / N deterioration. Thus, even if white balance correction is performed, a luminance signal with a good S / N can be provided.
[0016]
In the present embodiment, the control unit 110 has been described with reference to FIG. 2 so as to control the coefficients kr, kg, and kb according to the white balance gain Bwbg multiplied by the B signal. However, the white balance gain multiplied by the R signal is not limited. Coefficients kr, kg, kb may be controlled according to Rwbg, in which case the values r1, r2, g1, g2, b1, b2 of each coefficient are r1> r2, g1 <g2, b1 <b2 become.
[0017]
In this embodiment, signal processing using R, G, and B signals has been described. However, signal processing using cyan, magenta, yellow, and green can also be applied.
[0018]
(Embodiment 2)
FIG. 3 is a block diagram showing the configuration of the image processing apparatus according to the second embodiment of the present invention. 3, reference numerals 10, 11, and 12 denote multipliers, reference numerals 13, 14, and 15 denote γ means, reference numerals 16, 17, and 18 denote multipliers, reference numeral 19 denotes an adder, and reference numeral 110 denotes multipliers 16 to 16. Control means for controlling 18 coefficients, 30 is a Y matrix circuit for generating a luminance signal Y1, 31 is a high-pass filter (HPF) for extracting high-frequency components of the luminance signal Y2, and 32 is an adder. .
[0019]
The operation of the image processing apparatus configured as described above will be described below.
[0020]
Since the multipliers 10 to 12, the γ means 13 to 15, the multipliers 16 to 18, the adder 19, and the control means 10 are the same as those in the first embodiment, detailed description thereof is omitted. The difference from the first embodiment is that a Y matrix 30, an HPF 31, and an adder 32 are provided. The Y matrix 30 generates a first luminance signal (Y1) by multiplying Rγ, Gγ, and Bγ by fixed coefficients, for example, Y1 = 0.3 × Rγ + 0.59 × Gγ + 0.11 × Bγ. The HPF 31 extracts the high frequency component (YH) of the luminance signal (Y2) output from the adder 19, and the adder 32 adds the luminance signal Y1 and the high frequency component YH to output the luminance signal Y. .
[0021]
In the image processing apparatus configured as described above, as the white balance gain Bwbg increases, the coefficient kr increases and the coefficient kb decreases. Therefore, even if the white balance gain Bwbg increases and the S / N of Bγ tends to deteriorate. In the numerical formula shown in the first embodiment, the luminance signal Y2 (Y in the first embodiment) reduces the ratio of Bγ and increases the ratio of Rγ to suppress the deterioration of S / N. By configuring the high frequency component YH from the luminance signal Y2 in which the deterioration of S / N is suppressed, it is possible to provide a luminance signal having a good S / N regardless of the white balance correction at any color temperature.
[0022]
In this embodiment, signal processing using R, G, and B signals has been described. However, signal processing using cyan, magenta, yellow, and green can also be applied.
[0023]
【Effect of the invention】
As described above, according to the present invention, in an image processing apparatus that processes a plurality of color information signals obtained by converting a captured subject image, each signal level of the plurality of color information signals is adjusted in order to adjust the white balance of the subject. First adjusting means for adjusting the color independently, γ means for nonlinearly processing a plurality of color information signals whose levels are adjusted by the first adjusting means, and independent signal levels of the plurality of color information signals subjected to nonlinear processing A second adjusting unit that adjusts the color information signal, a combining unit that combines the plurality of color information signals level-adjusted by the second adjusting unit and outputs the resultant as a luminance signal, and a first adjusting unit according to an adjustment amount in the first adjusting unit. And a control means for controlling the adjustment amount of each of the plurality of color information signals in the adjustment means 2, so that a luminance signal with a good S / N can be obtained regardless of the color balance at any color temperature. A marked effect that can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of an image processing apparatus according to Embodiment 1 of the present invention. FIG. 2 is a schematic diagram for explaining the operation of control means of the image processing apparatus. FIG. 4 is a block diagram showing the configuration of an image processing apparatus according to FIG. 4. FIG. 4 is a block diagram showing the configuration of a conventional image processing apparatus.
10 to 12, 16 to 18 Multiplier 13 to 15 Gamma means 19 Adder 110 Control means

Claims (6)

In an image processing apparatus that processes a plurality of color information signals, a first adjustment unit that independently adjusts a signal level of each of the plurality of color information signals according to a white balance gain, and a level adjustment by the first adjustment unit Γ means for nonlinearly processing the plurality of color information signals processed, second adjusting means for independently adjusting the signal levels of the plurality of color information signals subjected to nonlinear processing, and level adjustment by the second adjusting means A combining unit that combines the plurality of color information signals and outputs a luminance signal; and controls an adjustment amount of each of the plurality of color information signals in the second adjustment unit according to an adjustment amount in the first adjustment unit and control means for said control means, when adjusting so as to increase the specific color information signal level at the first adjusting means, contact the second adjusting means When the adjustment is performed so that the level of the specific color information signal whose level has been increased by the first adjustment unit is decreased, and the specific color information signal level is adjusted to be decreased by the first adjustment unit, 2. An image processing apparatus according to claim 2, wherein adjustment is performed so as to increase the level of the specific color information signal whose level has been decreased by the first adjustment unit . In an image processing apparatus that processes a plurality of color information signals, a first adjustment unit that independently adjusts a signal level of each of the plurality of color information signals according to a white balance gain, and a level adjustment by the first adjustment unit Γ means for nonlinearly processing the plurality of color information signals processed, second adjusting means for independently adjusting the signal levels of the plurality of color information signals subjected to nonlinear processing, and level adjustment by the second adjusting means first combining means and a filter for extracting a high frequency component of said first luminance signal, the nonlinear processed plurality of color information signals to the first luminance signal by combining a plurality of color information signals Second combining means for combining the signals at an arbitrary ratio to obtain a second luminance signal, and third combining means for combining the high-frequency component of the first luminance signal and the second luminance signal for output . The above The image processing and control means for controlling the adjustment amount of each of the plurality of color information signals in said second adjusting means in accordance with the adjustment amount in one of the adjustment means. The control means, the first when adjusting so as to increase the specific color information signal level in the adjustment means, the particular color information signals raising the level in the first adjusting means in said second adjusting means When the first adjustment means is adjusted to lower the specific color information signal level, the second adjustment means is used to reduce the level by the first adjustment means. 3. The image processing apparatus according to claim 2 , wherein the color information signal is adjusted to increase the level of the color information signal. The control means, the first when adjusting so as to increase the specific color information signal level in the adjustment means, the particular color information signals raising the level in the first adjusting means in said second adjusting means The first adjusting means adjusts so that the level of at least one color information signal other than the specific color information signal whose level is increased by the first adjusting means is increased. When adjusting the specific color information signal level in the second adjustment unit, the second adjustment unit adjusts the specific color information signal level lowered by the first adjustment unit to increase the level. 2. The adjusting unit according to claim 2, wherein the level of at least one color information signal other than the specific color information signal whose level is lowered by the first adjusting unit is adjusted to be lowered. The image processing apparatus of the other two described. 5. The image processing apparatus according to claim 1, wherein the plurality of color information signals are R, G, and B.   5. The image processing apparatus according to claim 1, wherein the plurality of color information signals are yellow, cyan, magenta, and green.

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