JPH0716252B2 - Imaging device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus preferably implemented in a so-called color video camera or the like.

BACKGROUND ART With the increase in resolution of image pickup devices such as color video cameras and image reproduction devices such as color televisions, the modulation signal of the chroma signal is used in the composite signal (composite video signal) of the NTSC system, which is the standard system of color television in Japan. And the high frequency component of the luminance signal (a component close to the chroma modulation frequency) disturbs the screen. The one caused by the chroma signal is called "dot interference", and the one caused by the luminance signal is called "cross color". As a means for removing these interferences, there is a method of separating and outputting a luminance signal and a chroma signal from a color video camera which is an image pickup device.

However, in a single-plate image pickup apparatus in which the color signal output of the image pickup element alternately outputs red (R) and blue (B) color components for each horizontal scanning, as will be described later, on-screen At the color boundary, the image has a rough step-like boundary for every two scanning lines, which significantly deteriorates the image quality.

FIG. 3 is a diagram showing a part of an array of color filters provided on a solid-state image sensor of a color video camera. The solid-state image sensor forms pixels, and magenta (Mg) is formed on each pixel.
Four color separation filters of complementary colors of green (G), cyan (Cy), and yellow (Ye) are arranged in a matrix. Hereinafter, the above four colors will be represented by the Roman letters Mg, G, Cy, Ye in parentheses. Third
In the figure, for each horizontal scanning period (1H), for example, in an odd field, the (no) th pixel row of lines 1 and 12 and the (no + 1) th pixel row of lines l3 and l4 are (no +
2) Second, in the pixel columns of the lines l5 and l6, the signal charges of two pixels vertically adjacent to each other are sequentially read out from the left side to the right side in FIG.

In the even field, the lines (l2, l3) shifted by (ne) th by one line, the lines (l4, l5) by (ne + 1) th, and the like, in the same manner, the two vertically adjacent pixels are left or right in FIG. Are sequentially read. In this way (Mg + Cy)
(G + Ye), (Mg + Ye) and (G + Cy) are repeated in the horizontal direction alternately in every horizontal scanning period (1H),
The output signal component is, for example, in the first no, ne-th column in both the odd and even fields, {(2R + 3G + 2B) + (2R-G) sinωt} / 2 (1) In the next no + 1, ne + 1-th column It is represented by the color tone signal component of {(2R + 3G + 2B) + (2B-G) sinωt} / 2 (2).

FIG. 4 is a block diagram showing an electrical configuration of a video signal system of the color video camera 1 according to the prior art. From the solid-state imaging device 2 such as CCD (charge coupled device),
The image signal P including the color tone signal components represented by the first and second equations, which is the mixed output of the columns, passes through the sample hold circuit 3 and the low pass filter (LPF) 4 and the band pass filter (B
PF) and the detection circuit 6. From the image signal P input to the low pass filter 4, the luminance signal component (2R +
3G + 2B) / 2 is separated and output as the luminance signal Y to the line 1 via the luminance signal processing circuit 5.

From the image signal P input to the bandpass filter (BPF) and the detection circuit 6, the color tone signal 2R at the no and neth
When -G is no + 1, ne + 1, the tone signal 2B-G is separated and input to the color signal processing circuit 7. Color signal processing circuit 7
, A part of the luminance signal Y is input from the luminance processing circuit 5 via the line 12, and an operation is performed between the color tone signals 2R-G, 2B-G and the luminance signal Y to obtain no, ne. The color difference signal R-Y is generated in the, ... th column, and the color difference signal BY is generated in the no + 1, ne + 1 ,.

Referring to FIG. 3, the color filter array in the no, no + 2, no + 4, ... th column corresponds to the color difference signal RY, and no + 1, no +
The 3, no + 5, ... th color filter array is the color difference signal BY
You can see that it corresponds to. Odd field in Table 1
No, no + 1, no + 2, ... th and even fields ne, ne + 1, ne
The relationship of the color difference signals obtained corresponding to the +2, ...

The color difference signals R-Y and B-Y thus obtained are delayed by the delay circuit 8a for delaying one horizontal scanning period (1H) and the horizontal color difference (15.734 kHz in the NTSC system) fHz. Of the two color difference signals RY and BY, which are synchronized with each other through a synchronization circuit 8 including a line switch 8b which alternately switches the signal and the color difference signal which is not delayed.
Then, the encoder circuit 9 including the adder circuit 9c for adding the outputs of the modulation circuits 9a and 9b synthesizes the chroma signal C and outputs it to the line l3.

Problems to be Solved by the Invention The components of the color difference signals RY and BY included in the output of the chroma signal C obtained from the above-described prior art imaging device 1 are
Table 2 shows the columns of the odd fields no, no + 1, no + 2, no + 3, ... And the even fields ne, ne + 1, ne + 2, ne + 3 ,.

In Table 2, the columns no, no + 1, no + 2, ... Represent odd-numbered field scan lines, and the columns ne, ne + 1, ne + 2, ... Represent even-numbered field scan lines.

As is clear from Table 2, the same color difference signal component appears repeatedly every two scanning lines in each field. For example, focusing on odd fields, the first column no and the next column no +
1 has the same color difference signal (RY) no in all columns
1 and the next column no + 2 have the same color difference signal (BY) no + 1
Is appearing. The same applies to the even fields ne, ne + 1, ne + 2, ....

Now, as shown in FIG. 5, the upper right portion is the red area Ar,
Assuming a case where a screen A whose lower left portion is a black area Ab is imaged and reproduced on a monitor screen (not shown), a boundary D between a reproduced image red area Ar and a black area Ab and each scanning line no, ne, no + 1,
The ne + 1, no + 2, ne + 2, ... Correspond as shown in FIG. The shaded area indicates the red area Ar. An ideal reproduced image when the screen A is captured should naturally have the coloring state shown in FIG.

However, when the screen shown in FIG. 5 is imaged and reproduced by using the image pickup apparatus 1 according to the prior art, the color development region of the red portion on the reproduced screen is shown by the shaded portion in FIG. As a result, as shown in Table 2 above, each field becomes an image having a rough stepwise boundary for every two scanning lines. For this reason, the boundary that should be the virtual line d is not clearly known, resulting in a problem that the quality of the reproduced image is significantly deteriorated.

An object of the present invention is to solve the above technical problems, to provide an image pickup apparatus capable of deriving a video signal which makes a color boundary clear and is reproduced with high image quality.

Means for Solving the Problems The present invention includes an image pickup unit 2 for picking up an image of a subject, separation units 4 to 7 for separating an image signal output from the image pickup unit 2 into a luminance signal Y and a color tone signal, and a separation unit. Color difference signal creating means for creating a plurality of color difference signals RY, BY on the basis of the luminance signal Y and the color tone signal from, and the first chroma signal from the plurality of color difference signals RY, BY C1
And the first chrominance signal C1 are delayed by one horizontal scanning period to generate the second
A first delay circuit 21 for deriving a chroma signal C2, a first chroma signal C1 from the combining means 8 and 9, and a first delay circuit 2
Average value (C1 + C2) / 2 with the second chroma signal C2 from 1
Arithmetic averaging circuit for obtaining and deriving as the third chroma signal C0
22 and a second delay circuit 23 for delaying the luminance signal Y from the separating means 4 to 7 by one horizontal scanning period, and the third chroma signal C0 and the delayed luminance signal from the second delay circuit 23. An image pickup device characterized in that a screen is reproduced by using Y0.

According to the present invention, the first delay circuit 21 delays the first chroma signal C1 by one horizontal scanning period, and the averaging circuit 22 delays the first chroma signal C1 and the first delay circuit 21. The average value of addition with the second chroma signal C2 is calculated as the third chroma signal C0, and the third chroma signal C0 and the luminance signal
In order to eliminate the time difference from Y0, the luminance signal Y from the separating means 4 to 7 is delayed by one horizontal scanning period, and thus the third chroma signal C0 and the luminance signal delayed by the second delay circuit 23. Since the NTSC composite video signal is obtained by Y0 and the screen is reproduced, the chroma signal C (n) of the (n) th column in a certain field and one horizontal scanning period before that, that is, The third chroma signal is calculated as the arithmetic mean of the chroma signal C (n-2) two columns before.
C0 (n) will be obtained, so that it is possible to generate a region where the coloring brightness is 1/2 for every two scanning lines, and to make the part that develops color at 1/2 the brightness look thinner. Therefore, the boundary line δ can be displayed clearly for the first time.

Embodiment 1 FIG. 1 is a block diagram showing an electrical configuration of a video signal system of an image pickup apparatus 11 according to an embodiment of the present invention. From the solid-state image sensor 2 such as a CCD (charge coupled device), an image signal P including a color tone signal component represented by the first and second equations, which is a mixed output of the upper and lower two columns, passes through a sample hold circuit 3 and is low-passed. It is input to the filter (LPF) 4, the bandpass filter (BPF) and the detection circuit 6. From the image signal P input to the low pass filter 4, the luminance signal component (2R + 3G + 2
B) / 2 is separated and output as a luminance signal Y to the line 1 via the luminance signal processing circuit 5.

From the image signal P input to the bandpass filter (BPF) and the detection circuit 6, the color tone signal 2R−
When G is no + 1, ne + 1, the tone signal 2B-G is separated and input to the color signal processing circuit 7. Color signal processing circuit 7
, A part of the luminance signal Y is input from the luminance processing circuit 5 via the line 12, and an operation is performed between the color tone signals 2R-G, 2B-G and the luminance signal Y to obtain no, ne. The color difference signal R-Y is generated in the, ... th column, and the color difference signal BY is generated in the no + 1, ne + 1 ,.

A feature of the present invention is that a delay circuit 21 as a chroma signal generating means for generating a plurality of chroma signals C1 and C2 which keeps a constant time difference from a chroma signal C output from a modulation circuit 9 and a constant time difference described above are maintained. Input multiple chroma signals C
The calculation means 22 for adding and averaging 1 and C2 is provided, which will be described below.

However, in the present embodiment, the sample-hold circuit 3, the low-pass filter 4, and the band-pass filter as a separating unit that separates the image signal P obtained from the image sensor 2 that is an image-capturing unit that images a subject into a luminance signal and a color tone signal. 6
A luminance signal component and a color tone signal component are separated via

The luminance signal processing circuit 5 outputs the luminance signal Y to the line 1 from the luminance signal component, and the color signal processing circuit 7 as the color difference signal generating means for generating a plurality of color difference signals from the color tone signal causes the above-mentioned color tone signal component and the brightness. A plurality of color difference signals R-Y and B-Y are created by addition calculation of the signal components.
Further, the chrominance signal C is combined by the synchronization circuit 8 and the modulation circuit 9 which are synthesizing means for synthesizing the chrominance signal from the plurality of color difference signals RY and BY, and the chrominance signal C is output to the line l3.

The luminance signal Y derived on the line 1 is further delayed by the delay circuit 23.
Is output to the luminance signal output line l5 as the luminance signal Yo delayed by 1H via the chroma signal Co according to the present embodiment, which is output with a delay of approximately 1H, as described later. This is to eliminate the time difference between the luminance signal Yo and the chroma signal Co.

In the present embodiment, the chroma signal C derived from the modulation circuit 9 to the line l3 is divided into two, one is directly input to one of the averaging circuits 22 as the first chroma signal C1, and the other is passed through the delay circuit 21. Then, as the second chroma signal C2 with 1H delay, it is input to the other of the arithmetic mean circuit 22 in the same phase and at the same level as the first chroma signal C1, and the arithmetic mean of the first chroma signal C1 and the second chroma signal C2. (C1 + C2) / 2 is the chroma signal Co
Is output to the chroma signal output line l4. That is, the chroma signal Co (n) in a certain column (n) is the average of the chroma signal C (n) in the (n) column and the chroma signal C (n-2) 1H before that, that is, two columns before. Is output as.

Table 3 shows the chroma signal Co obtained when the image pickup device 11 according to the present embodiment is used to take an image of the screen A shown in the above fifth example.
The color difference signals R-Y and B-Y included in
no + 1, no + 2, no + 3, ... and even fields ne, ne + 1, ne
This is for each column of +2, ne + 3, .... Due to space limitations, the color difference signal R-Y is shown in Table 3 (a) as the color difference signal B-Y.
-Y is shown in Table 3 (b).

In Table 3 (a) and (b), columns no, no + 1, no + 2,
…, The scan lines of the odd fields are shown in columns ne, ne + 1, ne + 2,
…, Represents the scan lines of even fields.

FIG. 2 is a diagram showing a coloring situation of a reproduced screen based on Tables 3 (a) and 3 (b). Referring also to FIG. 6, since the chroma signal Co is output with a delay of approximately 1H in this embodiment, the column no in FIG. 6 corresponds to the column no + 1 in FIG. 2, for example. The shaded area is the red area Ar.

As is clear from Table 3, according to this embodiment, a region in which the red coloring luminance is 1/2 is generated for every two scanning lines.
In FIG. 2, the portion that develops at this 1/2 luminance is shown thinly. Under such a coloring condition, a half-colored portion appears to have half its length colored at full brightness. This is due to the illusion of human eyes, and therefore, in the screen A of FIG. 2, the boundary between the red area Ar and the black area Ab is as if the tip of the full-luminance coloring portion and the midpoint of the 1/2 coloring portion. It looks as if it is a continuous line δ. Moreover, this effect is remarkable as the distance from the screen A is long, and when the screen A is viewed at a sufficiently long distance, it looks like the color condition of the ideal reproduction screen shown in FIG. An imaging device that provides

Effects As described above, according to the present invention, the first delay circuit 21 delays the first chroma signal C1 by one horizontal scanning period to derive the second chroma signal C2. The luminance signal Y is supplied to the second delay circuit 23 in order to eliminate the time difference from the third chroma signal C0 by obtaining the arithmetic mean value of the first and second chroma signals C1 and C2.
Then, the luminance signal delayed by one horizontal scanning period is delayed by the third chroma signal C0 and the second delay circuit 23.
Since the NTSC composite video signal is obtained by Y0 and the screen is reproduced, the chroma signal C (n) of the (n) th column in a certain field and one horizontal scanning period before that, that is, 2 The third chroma signal C0 can be obtained as an arithmetic mean value with the chroma signal C (n-2) in the previous column, and therefore, the area in which the coloring luminance is halved can be reproduced every two scanning lines. Therefore, the boundary line δ can be clearly seen. In this way, the color boundaries on adjacent scanning lines in one field can be viewed as clear boundaries close to the ideal reproduction screen, and an image pickup apparatus capable of reproducing good image quality can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of a video signal system of an image pickup apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing a coloring state of a reproduction screen based on this embodiment, and FIG. 3 is an image pickup means. Showing part of the arrangement of color filters provided in FIG. 4, FIG. 4 is a block diagram showing the electrical configuration of a video signal system of the prior art, and FIG.
FIG. 6 is a diagram showing an image pickup screen, FIG. 6 is a diagram showing correspondence between the image pickup screen and horizontal scanning lines, FIG. 7 is a diagram showing an ideal coloring state of the reproduction screen, and FIG. 8 is a reproduction screen according to a prior art. It is a figure which shows the coloring situation of. 11 ... Imaging device, 2 ... Imaging means, 4 ... Low-pass filter,
5 ... Luminance signal processing circuit, 6 ... Band pass filter (BP
F) and detection circuit, 7 ... Color signal processing circuit, 8 ... Synchronization circuit, 9 ... Modulation circuit, 21 ... 1H delay circuit, 22 ... Addition / averaging circuit, A ... Screen, Ab ... Black area, Ar ... Red area, Co ... Chroma signal, Yo ... Luminance signal, l4 ... Chroma signal output line, l5
... Luminance signal output line

Claims (1)

[Claims] 1. An image pickup means 2 for picking up an image of a subject, separation means 4-7 for separating an image signal output from the image pickup means 2 into a luminance signal Y and a color tone signal, and a luminance signal Y from the separation means and a color tone. Color difference signal creating means for creating a plurality of color difference signals RY, BY based on the signals, and the first chroma signal C1 from the plurality of color difference signals RY, BY
And the first chrominance signal C1 are delayed by one horizontal scanning period to generate the second
A first delay circuit 21 for deriving a chroma signal C2, a first chroma signal C1 from the combining means 8 and 9, and a first delay circuit 2
Average value (C1 + C2) / 2 with the second chroma signal C2 from 1
Arithmetic averaging circuit for obtaining and deriving as the third chroma signal C0
22 and a second delay circuit 23 for delaying the luminance signal Y from the separating means 4 to 7 by one horizontal scanning period, and the third chroma signal C0 and the delayed luminance signal from the second delay circuit 23. An image pickup device characterized in that a screen is reproduced by using Y0.