JP4729058B2 - Video signal reproduction band changing device - Google Patents

Description

  The present invention relates to a reproduction band changing device.

  In a color single CCD, a color filter having a characteristic of transmitting each color component of R, G, or B is formed on a photodiode. The color filters have different arrangements for R and B and G. For this reason, the reproduction band of the R, G or B color signal output from the color single CCD is different for each color signal. For example, the reproduction band of the G color signal is wider than the reproduction bands of the R and B color signals.

  In order to improve the resolution of the image, the reproduction band may be widened. However, the reproduction band is determined for each color signal, and if the reproduction band is always expanded beyond the predetermined reproduction band, a false signal is generated and the image quality deteriorates. In order to remove the false signal, band limitation processing may be performed on the color signal, but band limitation processing for each color signal cannot be performed with an optical LPF (low pass filter).

  In addition, since the amount of noise increases in proportion to the reproduction band, even for a black and white video signal, if the reproduction band is widened to improve the resolution, the image quality may be deteriorated. For this reason, it has not been considered in the past to change the reproduction band.

  An object of the present invention is to change the reproduction band of a video signal.

  The video signal reproduction band changing device according to the present invention is characterized in that the video signal output from the solid-state electronic image sensor is input, and the reproduction band of the input video signal is changed and output according to a given change condition. To do.

  According to the present invention, the video signal output from the solid-state electronic image sensor is input to the reproduction band changing device. A change condition is given to the reproduction band changing device, and the reproduction band of the input video signal is changed according to the change condition.

  As the change condition is given, the reproduction band of the input video signal is changed. Therefore, even if the reproduction band is changed, the reproduction band can be set at any time, such as when the image quality of the image represented by the video signal does not deteriorate. Can be changed. If the image quality deteriorates, the reproduction band can be prevented from being changed.

  The solid-state electronic image pickup device is, for example, a single plate that has a color filter formed on a photoelectric conversion device and outputs a color video signal. In this case, color signal generating means for generating a plurality of color signals (including a plurality of luminance signals) from the color video signal output from the solid-state electronic image sensor is further provided. Further, the reproduction bands of the plurality of color signals generated by the color signal generation means will be changed. Then, a combining means for combining and outputting a plurality of color signals changed to the respective color reproduction bands in accordance with the ratio of colors included in the color image represented by the color video signal output from the solid-state electronic image pickup device Will be further provided.

  The degree of synthesis of a plurality of color signals varies depending on the color ratio. A composite video signal having an optimum color reproduction range corresponding to the color ratio is obtained.

  Depending on the amount of noise contained in the video signal output from the solid-state electronic image sensor, the number of pixels of the solid-state electronic image sensor, or whether the input video signal is after thinning processing, the reproduction band of the input video signal is determined. It is preferable to change the output.

  Noise can be suppressed by changing the reproduction band to be narrow. Further, since the identification of high frequency components becomes difficult as the number of pixels increases, it is considered more effective to remove false signals and noise by changing the reproduction band to be narrow. In addition, aliasing distortion may occur when thinning processing is performed, but aliasing distortion can be prevented from occurring by changing the reproduction band to be narrow. Of course, it is needless to say that the reproduction band can be changed.

  FIG. 1 shows an embodiment of the present invention, and shows a part of the structure on the light receiving surface of a CCD 1.

  A number of photodiodes 2 are arranged in the CCD 1 in the horizontal direction (column direction) and the vertical direction (row direction). These photodiodes 2 are arranged in odd rows for odd columns and in even rows for even columns (so-called honeycomb arrangement). Of course, odd columns may be arranged in even rows, and even columns may be arranged in odd rows.

  On the light receiving surface of the photodiode 2, an R color filter having a characteristic of transmitting a red light component, a B color filter having a characteristic of transmitting a blue light component, or a G color filter having a characteristic of transmitting a green light component Is formed. The letter “R” is attached to the photodiode 2 on which the R color filter is formed, and the letter “B” is attached to the photodiode 2 on which the B color filter is formed to form the G color filter. A letter “G” is attached to the photodiode 2. The odd-numbered photodiodes 2 are formed with G color filters, and the even-numbered photodiodes 2 are alternately formed with R color filters and B color filters on the same column. Although the photodiode 2 has a quadrangular shape as viewed from above, it is needless to say that other shapes such as a hexagon may be used.

  When four photodiodes 2 adjacent to each other among all the photodiodes 2 are extracted, a diamond shape 6 is obtained. Further, considering the photodiode 2 in which the G color filter is formed, when four photodiodes 2 adjacent to each other are extracted, a rectangular shape 7 is obtained. Further, considering the photodiode 2 in which the R color filter or the B color filter is formed, and extracting the four photodiodes 2 adjacent to each other, the four photodiodes 2 adjacent to each other are extracted from all the photodiodes. The resulting rhombus shape 8 is slightly larger than the rhombus shape 6. Because of this arrangement, the reproduction band changes as will be described later.

  A vertical transfer path 3 is formed on the right side (or the left side) of each column of the photodiodes 2. By applying a transfer pulse to the vertical transfer path 4, the signal charge accumulated in the photodiode 2 is transferred in the vertical direction.

  A horizontal transfer path 4 for transferring signal charges in the horizontal direction (in the opposite direction) is provided at the lowermost stage of the CCD 1 in accordance with a horizontal transfer pulse applied. When the signal charge transferred in the vertical transfer path 4 is applied to the horizontal transfer path 4, the signal charge is transferred in the horizontal direction and output to the outside through the amplifier circuit 5 as a video signal.

  2 to 4 show the reproduction band of the video signal.

  FIG. 2 shows a reproduction band of a video signal output from the CCD 1 when a gray subject is imaged using the CCD 1 shown in FIG.

  When the subject is gray, a video signal obtained based on the signal charges accumulated in all of the photodiodes 2 can be used to reproduce an image representing the gray subject. For this reason, the reproduction band (zone 1) corresponds to the arrangement of the photodiodes 2 of the CCD 1 and has a rhombus shape (corresponding to the rhombus shape 6 described above). The reproduction band is obtained by connecting points of 1/2 of the spatial frequency fs (= Nyquist frequency fn) and negative spatial frequency −fs / 2.

  FIG. 3 shows a reproduction of the video signal obtained based on the signal charge accumulated in the photodiode 2 in which the G color filter is formed among the video signals obtained when the subject is imaged using the CCD 1 shown in FIG. Indicates the bandwidth.

  The reproduction band (zone 2) of the video signal obtained based on the signal charge accumulated in the photodiode 2 in which the G color filter is formed corresponds to the arrangement of the photodiodes 2 in which the G color filter is formed. Yes. The reproduction band has a quadrangular shape (corresponding to the quadrangular shape 7 described above). Each point of the half of the Nyquist frequency is connected to a rectangle.

  FIG. 4 is obtained based on the signal charges accumulated in the photodiode 2 in which the B color filter or the R color filter is formed among the video signals obtained when the subject is imaged using the CCD 1 shown in FIG. The reproduction band of the video signal is shown.

  The reproduction band (zone 3) of the video signal obtained based on the signal charges accumulated in the photodiode 2 in which the B color filter or the R color filter is formed is a photo in which the B color filter or the R color filter is formed. This corresponds to the arrangement of the diodes 2. The reproduction band has a rhombus shape (corresponding to the rhombus shape 8 described above). Each point of the half frequency of the Nyquist frequency fn is connected in a diamond shape.

  FIG. 5 shows the reproduction bands shown in FIGS. 2 to 4 superimposed.

  As can be seen from FIG. 5, the reproduction band (zone 1) of the video signal output from the CCD 1 when the gray color object is imaged using the CCD 1 shown in FIG. Then, the reproduction band (zone 2) of the video signal obtained based on the signal charges accumulated in the photodiode 2 in which the G color filter is formed has the next wide reproduction band. Finally, a reproduction band (zone 3) of the video signal obtained based on the signal charge accumulated in the photodiode 2 in which the B color filter or the R color filter is formed.

  FIG. 2 is a block diagram showing a part of the electrical configuration of the digital still camera.

  A CCD 1 shown in FIG. 1 is used as a solid-state electronic image sensor. When the subject is imaged by the CCD 1, a video signal representing the subject image is output. The video signal is input to the luminance signal generation circuit 11 and the color difference signal generation circuit 13.

  The luminance signal generation circuit 11 generates two luminance signals Y1 and Y3 from the input video signal. The luminance signal Y1 has a reproduction band of zone 1 shown in FIG. The luminance signal Y3 has a reproduction band of zone 3 shown in FIG. The luminance signal Y1 having the reproduction band of zone 1 and the luminance signal Y3 having the reproduction band of zone 1 can be generated by using two filters having the reproduction band characteristic of zone 1 and the reproduction band characteristic of zone 3, respectively. Of course, it may be generated using a single filter that can switch both the reproduction band characteristics of zone 1 and the reproduction band characteristics of zone 3. The generated luminance signals Y1 and Y3 are input to the weighted addition circuit 12.

  The weighting addition circuit 12 generates and outputs a weighted luminance signal YH by changing the ratio of the luminance signals Y1 and Y3 based on the magnitude of a weighting signal (change condition) Cd given as will be described later. Is.

  The color difference signal generation circuit 13 generates Cr and Cb color difference signals from the input video signal. The generated color difference signals Cr and Cb are input to the absolute value addition circuit 14 and the resolution conversion circuit 15.

  In the absolute value addition circuit 14, the absolute values | Cr | and | Cb | of the respective color difference signals are added to generate a weighting signal Cd. That is, the weighting signal Cd is generated according to Equation 1. The weighting signal Cd indicates the amount of red component and blue component included in the video signal output from the CCD 1.

  Cd = | Cr | + | Cb |

  In the weighting addition circuit 12, the luminance signal YH after the weighting process is generated according to Equation 2 according to the value of the weighting signal Cd output from the absolute value addition circuit 14.

YH = {Cd × Y3 + (Th−Cd) × Y1} / Th Equation 2
However, Th is a threshold value.

  FIG. 7 shows the relationship between the value of the weighting signal Cd and the luminance signals Y1 and Y3.

  When the weighting signal Cd is 0, the ratio of the luminance signal Y1 is 100% and the ratio of the luminance signal Y3 is 0. As the weighting signal Cd gradually increases from 0, the ratio of the luminance signal Y1 decreases, and conversely, the ratio of the luminance signal Y3 increases. When the weighting signal Cd exceeds the threshold Th, the ratio of the luminance signal Y1 becomes 0 and the ratio of the luminance signal Y3 becomes 100%. A luminance signal YH having such a ratio of the luminance signals Y1 and Y3 is generated in the weighted addition circuit 12. The generated luminance signal YH is input to the resolution conversion circuit 15 shown in FIG.

  The resolution conversion circuit 15 converts the resolution (number of pixels) of the image represented by the input luminance signal YH and color difference signals Cr and Cb. The resolution is determined according to the mode set by a mode switch (not shown).

  The luminance signal output from the resolution conversion circuit 15 is input to the contour correction circuit 16, and the color difference signal is input to the color correction circuit 17.

  In the contour correction circuit 16, the contour correction processing of the image represented by the input luminance signal is performed. Further, the color correction circuit 17 performs a contour correction process on the image represented by the input color difference signal.

  When the luminance signal output from the contour correction circuit 16 and the color difference signal output from the color correction circuit 17 are given to the display device, the captured image is displayed.

  As the amount of red component and blue component contained in the video signal output from the CCD 1 increases, the ratio of the luminance signal Y3 in which the reproduction band corresponding to the red component and blue component becomes dominant as shown in FIG. Become. Since a luminance signal having a reproduction characteristic corresponding to the color of the subject can be obtained, generation of false signals, noise, etc. can be prevented in advance, and an image with high resolution can be obtained.

  The embodiment described above uses the CCD 1 that outputs a color video signal as shown in FIG. 1, but the embodiment according to the present invention can also use a CCD that outputs a black and white video signal.

  FIG. 8 is a block diagram showing a part of the electrical configuration of a digital still camera using a monochrome CCD 1A as an image sensor.

  A luminance signal is output from the CCD 1A and input to the reproduction band changing circuit 21.

  The reproduction band changing circuit 21 includes a filter having a reproduction band characteristic of zone 1 and a filter having a reproduction band characteristic of zone 3 as in the weighted addition circuit 12. In the reproduction band changing circuit 21, the luminance signals Y1 and Y3 described above are generated.

  The generated luminance signals Y1 and Y3 are input to the weighted addition circuit 22.

  The weighted addition circuit 22 outputs the luminance signals Y1 and Y3 by changing the ratio according to a given weighting coefficient.

  In this embodiment, the weighting factors include the amount of noise included in the luminance signal output from the CCD 1 and the number of pixels of the CCD 1A. When the video signal output from the CCD 1A is thinned, the thinning rate may be included in the weighting coefficient.

  The amount of noise increases in proportion to the reproduction band. For this reason, when the priority is given to an image with a large amount of noise or noise reduction, the reproduction band is narrowed. That is, the ratio of the luminance signal Y3 is made larger than the luminance signal Y1.

  In addition, when the number of pixels is large, it becomes impossible to identify the high frequency components of the image, so the necessity for the high frequency components is reduced. For this reason, the reproduction band is narrowed when the number of pixels is large. This makes it possible to cut off false signals and noise.

  Further, when thinning processing is performed, the reproduction band is narrowed in order to prevent false signals due to aliasing distortion in the thinning processing. For example, in the case of a thinning rate such that the thinning is ½ (area ratio ¼), the luminance signal Y3 will be used.

  In the embodiment described above, the luminance signal having the reproduction band of zone 1 and zone 3 is synthesized, but the luminance signal having the reproduction band of zone 2 may also be generated and synthesized.

A part of the structure on the light receiving surface of the CCD is shown. The reproduction band is shown. The reproduction band is shown. The reproduction band is shown. The reproduction band is shown. 2 shows a part of the electrical configuration of a digital still camera. The ratio of the weighted signal and the luminance signal is shown. 2 shows a part of the electrical configuration of a digital still camera.

Explanation of symbols

1,1A CCD
2 Photodiode
11 Luminance signal generation circuit
12, 22 Weighted addition circuit
21 Reproduction band change circuit

Claims (2)

A video signal reproduction band changing device for inputting a video signal output from a solid-state electronic image sensor, changing a reproduction band of the input video signal according to a given change condition, and outputting the video signal.
The solid-state electronic imaging device is a single plate that has a color filter formed on a photoelectric conversion device and outputs a color video signal.
A luminance signal generating means for generating a plurality of luminance signals having different reproduction bands from the color video signal output from the solid-state electronic image sensor;
A plurality of luminance signals having different reproduction bands generated by the luminance signal generating means are combined and output in accordance with a ratio of colors included in a color image represented by a color video signal output from the solid-state electronic image sensor. Synthesis means,
Reproduction band change device equipped with. The photoelectric conversion elements are arranged in odd rows for odd columns, even rows for even columns, or even rows for odd columns, and odd rows for even columns. ,
The odd-numbered photoelectric conversion elements are formed with a G color filter having a characteristic of transmitting a green light component, and the even-numbered photoelectric conversion elements are formed with an R color filter having a characteristic of transmitting a red light component and a blue color filter. The B color filters having the characteristic of transmitting the light component are alternately formed on the same column,
The luminance signal generating means corresponds to the first luminance signal having a reproduction band corresponding to the arrangement of the photoelectric conversion elements and the arrangement of the photoelectric conversion elements in which the B color filter or the R color filter is formed. A second luminance signal having a reproduction band, and
The synthesizing means has {Cd × (second luminance signal) + (threshold−Cd) × (first luminance signal)} / threshold (where Cd = | Cr | + | Cb |). Output
The reproduction band changing device according to claim 1.

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