JP2007158579A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of an imaging apparatus having an imaging element with a plurality of division areas that a level difference between the areas may be caused in a video image when the imaging apparatus photographs a uniformly achromatic colored object. <P>SOLUTION: The imaging apparatus determines a detection region and a correction region to each area in two adjacent areas, detects variations in signals of each area and a level difference between the area in the detection region, corrects the correction region when they are respectively a reference value or below, so that even when the uniformly achromatic colored object is photographed even by a boundary of the areas, the signal level of the part can definitely be corrected. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus having an image pickup element having a plurality of divided areas, and more particularly to a means for correcting a level difference of a video signal between adjacent areas.

  A configuration example of a conventional digital video camera will be described with reference to FIG. The optical signal that has passed through the lens 1 is input to the CCD 3 via the diaphragm 2. The CCD 3 has divided areas divided into several parts in all the effective pixels, and a driving circuit is provided in each divided area. Here, a CCD having two divided areas (Ach and Bch) is taken as an example. The CCD 3 is driven by the pulse waveform output from the TG 4. A signal photoelectrically converted by the CCD 3 is input to an AFE 5 having a CDS circuit and an AGC amplifier that perform correlated double sampling for removing reset noise, and an A / D converter that converts an analog signal into a digital signal. Then, after being converted into a digital signal, it is input to the multiplex 6. The multiplex 6 performs multiplex processing for combining the data DAch for each CCD divided area output from the AFE 5 and the DBch into one image. Correct differences between channels as part of the multiplex process. In that case, after correcting the linearity of each channel, the gain difference between the channels is corrected. The corrected signal is input to the camera signal processing circuit 7 after being synthesized. The camera signal processing circuit 7 performs YC separation, performs luminance signal processing and color signal processing, and generates a video signal. At the time of still image shooting, it is sent to the still image recording medium 8. At the time of moving image shooting, it is sent to the moving image recording medium 10 through the video signal processing circuit 9 and is also input to the LCD 12 through the display circuit 11 and displayed. The CPU 13 sends signals to the camera signal processing circuit 7 and the video signal processing circuit 9 and controls them.

  Multiplex 6 combines 2ch output. The level difference between channels is corrected here. In this case, the correction method corrects the gain difference generated between the channels after correcting the linearity of each channel. The correction value is measured in advance for each product. At this time, the correction value is measured in consideration of the temperature condition. The output of each channel is corrected using the correction value obtained in this way, and then synthesized.

Further, as a method of correcting a density shift occurring on the boundary surface, a method of acquiring a correlation value between pixel signals for each region near the boundary of each divided area and correcting the pixel signal based on the acquired correlation value (For example, refer to Patent Document 1).
JP 2002-335454 A

  However, due to subtle deviations in the temperature characteristics and correction data of the CCD, when shooting at low illumination or shooting a uniform achromatic object, a level difference between channels occurs as an image, which degrades image quality. There are things to do. The magnitude of the level difference and the illuminance of the subject when the level difference occurs vary depending on the product.

  The present invention has been made paying attention to the above-mentioned problems, and if a uniform achromatic subject is photographed even at a part of the boundary of the area, the signal level is corrected limitedly in that part. An object of the present invention is to provide an imaging device that can perform the above-described operation.

  In order to achieve the above object, the present invention comprises the following arrangement.

  (1) In an imaging device in which all pixels of a solid-state imaging device are divided into several divided areas, each adjacent area has a video signal detection area and a correction area, and each area has a detection area. Means for detecting variations in the video signal, means for detecting the level difference of the video signal in the detection area between the areas, and means for correcting the level difference of the video signal between the areas in the correction area, An imaging apparatus, wherein correction is performed if a variation and a level difference between the signals are equal to or less than a reference value.

  (2) In an image pickup apparatus in which all pixels of a solid-state image pickup device are divided into several divided areas, there are means for detecting a level difference between the divided areas and correcting the level difference over the entire screen. For each area, each area has a detection area and a correction area for the video signal, detects a variation in the video signal in the detection area in each area, and detects a level difference in the video signal in the detection area between the areas. An image pickup apparatus comprising: a means for correcting a level difference of a video signal between areas of the correction area, wherein the correction is performed if the variation and the level difference of the signal are equal to or less than a reference value;

  That is, each channel has a detection area and a correction area, detects a variation in the video signal in the detection area of each channel, detects a level difference between channels of the video signal in the detection area of each channel, and If the level difference is equal to or less than a predetermined reference value, it can be determined that the detection area is uniform and achromatic, and therefore the corresponding correction area signal is corrected.

  If a step is generated only during low-illuminance shooting, the above detection and correction are performed only when the gain is increased.

  According to the present invention, in the case of an achromatic object having a uniform luminance level, the vicinity of the joint is corrected, so that it is not necessary to perform a difficult low-level step detection, and the level difference between channels can be reduced. In addition, in order to detect and determine signals of several lines, only a uniform level achromatic subject portion is corrected even in a scene where a uniform level achromatic subject and a different subject are mixed in a joint portion of a certain field. be able to.

  The best mode for carrying out the present invention will be described below based on examples.

  A configuration example of the digital video camera of this embodiment is shown in FIG. The optical signal that has passed through the lens 1 is input to the CCD 3 via the diaphragm 2. The CCD 3 has divided areas divided into several parts in all the effective pixels, and a driving circuit is provided in each divided area. Here, a CCD having two divided areas (Ach and Bch) is taken as an example. The CCD 3 is driven by the pulse waveform output from the TG 4. A signal photoelectrically converted by the CCD 3 is input to an AFE 5 having a CDS circuit and an AGC amplifier that perform correlated double sampling for removing reset noise, and an A / D converter that converts an analog signal into a digital signal. Then, after being converted into a digital signal, it is input to the multiplex 6. The multiplex 6 performs multiplex processing for combining the data DAch for each CCD divided area output from the AFE 5 and the DBch into one image. The synthesized signal is input to the camera signal processing circuit 7. Inside the camera signal processing circuit 7, after the YC separation by the YC separation circuit, it passes through the YC level detection circuit that detects the level of luminance and color difference, and the detected signal is judged by the judgment circuit. If correction is necessary, the signal passes through a correction circuit, and thereafter, luminance signal processing and color difference signal processing are performed in a camera signal processing circuit to generate a video signal. At the time of still image shooting, it is sent to the still image recording medium 8. At the time of moving image shooting, it is sent to the moving image recording medium 10 through the video signal processing circuit 9 and is also input to the LCD 12 through the display circuit 11 and displayed.

  The camera signal processing circuit 7 will be described in detail. In this embodiment, an example is shown in which detection and correction are performed using a Y signal (luminance signal) and an RY / BY signal (color difference signal) as a video signal. The YC separation circuit receives a signal obtained by synthesizing the outputs of two channels in the multiplex 6. In the YC separation circuit, the RGB signal is converted into a Y signal (luminance signal) and an RY / BY signal (color difference signal). After conversion, the signal is sent to the YC level detection circuit. The YC level detection circuit detects a value capable of determining the variation of each channel of the luminance signal and the color difference signal and a value capable of determining the level difference between the channels among the signal values of the predetermined detection region. . In this embodiment, the aforementioned values are the maximum value and the minimum value, and those described later are the average values. The detected value is sent to the determination circuit. The determination circuit first determines for each channel whether or not the difference between the maximum value and the minimum value of the luminance signal is within a predetermined reference value in the detection region. The same is done for the color difference signal. Next, it is determined whether or not the difference between the average value of the luminance signal of one channel and the average value of the luminance signal of the other channel is within a predetermined reference value. The same is done for the color difference signal. If it is within the reference value in both determinations, the signal is sent to the correction circuit. The correction circuit performs correction in a predetermined correction area. This will be described in more detail with reference to the drawings.

FIG. 2A shows the detection and correction area. FIG. 2-b shows an enlarged view near the area. Each pixel has a corresponding luminance signal and color difference signal. In this embodiment, the detection area is 3 lines of n pixels, and the correction area is 1 line of n pixels. Since the detection region is carried out in three lines when the signal processing is performed on _{h l + 3 lines,} signals up _b n ~a _n in the _{h l +} 2 _~h l + ₄ lines of the signal becomes the detection area. Among the signal values in this area, the maximum value, minimum value, and average value are detected.

  Next, the discrimination circuit will be described with reference to FIG. Here, for the sake of simplicity, a luminance signal for one horizontal line will be described. The upper part of FIG. 3 shows the captured image, and the lower part shows the luminance signal output of the a, b, and c lines on the image.

  In the line a, the difference between the signal level maximum value and the minimum value is within the reference value in the detection region of each channel, and the difference between the channels of the average value in the detection range is also within the reference value, so correction processing is performed.

  Next, in line b, the difference between the maximum value and the minimum value of the Bch signal is within the reference value, but in Ach, the difference between the maximum value and the minimum value of the signal exceeds the reference value, so this line is included. No correction is performed in the area.

  In the c line, the difference between the maximum value and the minimum value of the signal in each channel is within the reference value, but the correction is not performed because the difference in the average value between the channels exceeds the reference value. The same determination is performed on the color difference signal. In this embodiment, this determination is performed for three lines.

If it is determined that correction is necessary when the line signal processing for the h _{l + 3} shown in FIG. 2 are performed signal b _n ~a _n in the h _{l + 3} line signals are corrected.

  FIG. 4 shows the correction method of this embodiment. FIG. 4 shows the nth signal from the boundary between channels in a signal of one line. If the m-th uncorrected signal of each channel is Am, Bm, and the corrected signal is Am ′, Bm ′, the corrected signal is

It is represented by

  If correction is performed using this equation, as shown in FIG. 4, the signal levels of Ach and Bch are close to each other in the vicinity of the boundary, and the nth signal is close to the original signal. Is difficult to see, and the difference between the correction area and the boundary outside the correction area can be reduced, and natural correction is possible. Even if correction is performed in a state where no difference has occurred, since there is no difference in the signal from the beginning, there is no significant change in calculation. The corrected signal is sent to the camera signal processing circuit to generate a video signal.

  In the correction method of the present embodiment, in an imaging apparatus having a plurality of outputs, the level difference is corrected limitedly when a uniform and achromatic object in which the level difference between channels is conspicuous is easily noticed. It is possible to correct the signal level difference between channels without detecting the level difference. Further, since detection and correction are performed by limiting the number of horizontal lines, even when uniform and achromatic parts are mixed in the same field, only uniform and achromatic parts can be corrected.

It is a schematic block diagram of the digital video camera of the Example of this invention. It is explanatory drawing of the detection area | region of the Example of this invention, and a correction | amendment area | region. It is a figure for demonstrating the discrimination method of the Example of this invention. . It is explanatory drawing of the example of a correction | amendment of the Example of this invention. It is a schematic block diagram of the conventional digital video camera.

Explanation of symbols

1 Lens 2 Aperture 3 CCD
4 TG
5 AFE
6 Multiplex 7 Camera signal processing circuit 8 Still image recording medium 9 Video signal processing circuit 10 Movie recording medium 11 Display circuit 12 LCD
13 CPU

Claims (6)

  In an imaging device in which all pixels of a solid-state imaging device are divided into several divided areas, each of the adjacent two areas has a video signal detection area and a correction area, and the video signal of each area detection area Means for detecting the variation of the video signal, means for detecting the level difference of the video signal in the detection area between the areas, and means for correcting the level difference of the video signal between the areas of the correction area. An image pickup apparatus that performs correction when a signal level difference is equal to or less than a reference value.   In an imaging device in which all pixels of a solid-state imaging device are divided into several divided areas, the image pickup device has means for detecting a level difference between the divided areas and correcting the level difference over the entire screen. Each area having a detection area and a correction area for the video signal, detecting a variation in the video signal in the detection area in each area, and detecting a level difference in the video signal in the detection area between the areas; An imaging apparatus comprising means for correcting a level difference of a video signal between areas of the correction area, and correcting if the variation and the level difference of the signal are equal to or less than a reference value.   The imaging apparatus according to claim 1, wherein the detection and the correction are performed using a signal having an arbitrary number of lines.   The imaging apparatus according to claim 2, wherein the detection and the correction are performed using a signal having an arbitrary number of lines.   The imaging apparatus according to claim 1, wherein the detection and the correction are performed only at low illuminance.   The imaging apparatus according to claim 2, wherein the detection and the correction are performed only at low illuminance.