JP2555007B2 - False color signal reduction device for color video camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video camera, and more particularly to a method for reducing a false color signal generated in a bright and dark edge portion of an image pickup screen.

[Background of the Invention]

In a single-plate color video camera using a solid-state image sensor, which has become widespread in recent years, for example, a mosaic-type color separation filter as shown in FIG. 1 is arranged on each pixel of the solid-state image sensor. The solid-state image sensor scans the signal of each pixel arranged on the light receiving surface with a pulse applied from the outside and outputs it in order. For example, in the case of an image sensor capable of reading two lines at the same time, as shown in FIG. 2, white (W), cyan (C _Y ), white, cyan, ... And yellow (Ye) in one horizontal scan. ，
Simultaneously read out the signals on two lines: white, yellow, white. This 2
Luminance signal required for obtaining a composite color signal of the NTSC rows of signal and red (R), and although obtain a blue (B) signal, R represents by performing the calculation of W-C _Y, also, B is The signal is reproduced by the calculation of W-Ye.

However, when the signal is reproduced by such a calculation, as shown in FIG.
And C _Y , or between W and Ye filters, a false color signal not present in the subject is generated, degrading the image quality.

Therefore, in a color video camera using a mosaic filter which has been generally used conventionally, a color signal erasing circuit for attenuating a color signal by using an edge signal of a subject is used.

FIG. 4 shows an example of a false color erasing circuit which has been conventionally used.

An arithmetic circuit 1 is a circuit for detecting an edge of an image. The subtraction circuit 1 has a wideband video signal A,
A narrow band video signal B is added and the edge signal is detected by the method of taking the difference between A and B. The edge signal thus taken out is applied to the false color signal suppressing circuit 3 via the low-pass filter 2. 3.58MH for the false color signal suppression circuit 3
A modulated chroma signal C of z is added, and C is amplitude-modulated according to the amplitude of the edge signal. As a result, in the portion where the edge signal exists, the chroma signal is suppressed and the saturation is lowered.

Since this false color signal suppression method suppresses all the color information in the vicinity of the edge, it causes an unnatural feeling depending on the subject, leading to deterioration of image quality.

[Object of the Invention]

An object of the present invention is to provide a false color signal reduction method that has less side effects on a color signal by separating and reducing false signal components included in the color signal.

[Outline of Invention]

A solid-state camera using a complementary color filter calculates a color signal from signals corresponding to two types of color filters. As a result, a negative color signal that does not actually exist may occur at the edge portion of the image. In the present invention, false color signals are reduced by detecting and deleting such abnormal portions.

Example of Invention

 Hereinafter, the details of the present invention will be described using examples.

FIG. 6 shows an embodiment circuit which satisfies the gist of the present invention.
FIG. 5 is a diagram for explaining the mechanism of false color signal generation, and the operation of the circuit of FIG. 6 will be described with reference to this diagram.

FIG. 5 (a) is a diagram in which only horizontal color filters for one line are extracted. E and F show two types of color filters that transmit different color light components, and E is a color filter that transmits polychromatic light. Suppose you do.

Assuming that a strip-shaped object consisting of a bright part and a dark part hits the position shown in FIG. 5A, the output signals corresponding to the E and F filters are (B) and (C). .
The signals of (b) and (c) are added to the input units 10 and 11 of FIG. 6, the signal of (c) is delayed by the delay circuit 12, the phases of E and F are matched, and the difference between the two is calculated by the subtraction circuit 13. When a signal is created, the signal shown in Fig. 5 (d) is obtained.

As described above, in a color video camera using a complementary color filter, a color signal is obtained by calculating two kinds of signals, but in the edge portion of the image, a false color signal indicated by a shaded portion in FIG. Appears and significantly deteriorates the image quality.

The circuits shown at 14 to 19 in FIG. 6 eliminate or reduce this spurious signal. Circuit 14 is a circuit for clip a negative signal, negative false signals by the action of this circuit, namely fifth view of (d) the (E ₄ -F ₄₎ is removed. The sample-hold circuit 15 and the low-pass filter circuit 16 are circuits for taking out the low-frequency components of the output signal of the circuit 14, and a signal (FIG. 5 (E)) whose adjoining is close to its average value is obtained. In other words, a false positive signal (E ₂ -F ₂₎ and the adjacent signal _{(E 1 -F 1) (E} 3
-F ₃ ), the average value of (E ₁ −F ₁ ) and (E ₃ −F ₃ ) is obtained from the output of the low-pass filter circuit 16, and (E ₁ − F ₁ ) and (E ₃ −
If a signal having an average value of F ₃ ) or more is deleted, the positive false signal component can be significantly reduced. Delay circuit 17 is circuit 14
The output signal of FIG. 5 and the output signal of the circuit 16 are phase-matched. The signal phase-matched by the delay circuit 17 has a level higher than that of the clip circuit 18 shown in FIG. Clip the signal and obtain the signal shown in (f). Since the positive false signal portion (E ₂ −F ₂ ) of the signal (d) is deleted from this signal (f), the false signal is reduced by passing this signal (f) through the low-pass filter 19. A good color signal can be obtained.

After the signal output terminal 20 in FIG. 6, 15, 16, 17, 18, 19
By connecting the circuit of No. 1 and performing the above-mentioned signal operation again, the positive false signal can be further reduced.

〔The invention's effect〕

As described above, according to the present invention, it is possible to efficiently reduce the false color signal of the solid-state image sensor having the complementary color filter, and thus it is possible to eliminate the image quality deterioration due to the removal of the false signal.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a mosaic color separation filter, FIG. 2 is a view showing signals at the time of simultaneous reading of two lines, and FIG.
FIG. 4 is an explanatory diagram showing a generation state of a false color signal, FIG. 4 is a block diagram showing an example of a conventional false color signal erasing circuit, FIG. 5 is an explanatory diagram of a false color signal generation mechanism, and FIG. FIG. 3 is a block diagram showing one example. 12 …… Delay circuit, 13 …… Subtraction circuit, 14 …… Clip circuit, 15 …… Sample hold circuit, 16 …… Low pass filter, 17 …… Delay circuit, 18 …… Clip circuit, 19 …… Low pass filter.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Naoki Ozawa 1-280 Higashi Koigakubo, Kokubunji City Central Research Laboratory, Hitachi, Ltd. (72) Inventor Takeshi Ogino 1410 Inada, Katsuta-shi, Hitachi Ltd. Tokai Factory, Hitachi Ltd.

Claims (1)

(57) [Claims] 1. A solid-state imaging device comprising a color filter in which a first filter element and a second filter element having a complementary color relationship are regularly arranged adjacent to each other, and a solid-state image sensor obtained from the first filter element. And a color signal containing a false signal by delay means for delaying the first output signal according to the rule and subtraction means for subtracting the output of the delay means from the second output signal obtained from the second filter element. And a first clip circuit for removing or reducing a false signal from the color signal, the first clip circuit removing a negative signal in the output of the subtracting unit, and the output of the first clip circuit. Average value detection means for obtaining a signal in the vicinity of the average value of
Second clipping means for removing a signal of a higher level than the output of the average value detecting means from the output of the first clipping circuit, and a false color signal by low-pass filtering the output from the second clipping means. A false color signal reducing apparatus for a color video camera, comprising: a false signal reducing / removing means including a means for detecting a color signal from which the color signal has been removed.