JPH0576016A - Chrominance signal phase compensating circuit - Google Patents

Abstract

PURPOSE:To provide a chrominance signal phase compensating circuit which prepares tow color difference signals by a time-division from RGB signals whose time phases are matched with each other, and whose low-pass frequency characteristics are almost matched. CONSTITUTION:This circuit is equipped with a converting part 1 which time- divides R and B video signals, and outputs it at a doubled sampling frequency rates, interpolating filter 2 which inputs the output signal of the converting part 2, and allows the time phase characteristic to be matched with that of the G signal, low-pass filter 5 which inputs the G signal, and allows the low-pass frequency characteristic to be matched with those of the R and B signals, delay part 3 which delays the output signal of the low-pass filter 5, and outputs it at the doubled sampling frequency rate, and subtracter 4 which generates an R-G signal and a B-G signal from the output signal of the delay part 3 and the output signal of the interpolating filter 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal phase compensating circuit for compensating the phase of a color signal of a consumer three-panel video camera using a spatial pixel shift method.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of an example of a color signal phase compensating circuit of a conventional three-panel video camera for consumer use, which is based on a generally used spatial pixel shift method. In FIG. 3, 1 is a red and blue digital video signal (hereinafter, R signal,
B signal) is time-divided and output at a double sampling frequency rate, 2 is an interpolation filter having the output signal of the conversion unit 1 as an input, and an interpolation filter having a characteristic of 1 + Z ^-2 , 3 is green digital A delay unit 4 for compensating a delay of a video signal (hereinafter abbreviated as a G signal) with respect to R and B signals and outputting at a double sampling frequency rate is a delay unit 3.
Is a subtracter that generates an R-G signal and a B-G signal from the output signal of 1 and the output signal of the interpolation filter 2.

In the conventional color signal phase compensating circuit of the consumer-use three-plate type video camera constructed as described above, R,
G and B signals are input, but since the spatial pixel shift method that normally prevents the occurrence of moire is adopted, the G solid-state image sensor is horizontally displaced from the R and B solid-state image sensors by half a pixel. ing. The R and B signals are first time-divided by the conversion unit 1, and the time-division R and B signals are output at a rate of twice the sampling frequency. The conversion unit 1 includes, for example, a D-type flip-flop 1 that latches a signal at a sampling frequency as shown in FIG. 4, and a selector 2 that selects one of an R signal and a B signal using a sampling clock as a control signal.
And a D-type flip-flop 3 that latches a signal at twice the sampling frequency. The interpolation filter 2 is a circuit that creates R and B signals that are in time phase with the G signal, has the characteristic of 1 + Z ⁻² , and has the output signal of the conversion unit 1.
The addition result of the signals passed through two D-type flip-flops for latching the output signal at twice the sampling frequency is output. The G signal is compensated for the delay of the R and B signals generated in the conversion unit 1 and the interpolation filter 2 by the delay unit 3,
The sampling frequency is doubled. The subtracter 4 uses the output signal of the delay unit 3 and the output signal of the interpolation filter 2 which have a temporal phase from the color difference signals RG and B-.
Make a G signal. The R-G signal and the B-G signal are output from the subtractor 4 at a double sampling frequency rate. FIG. 5 shows frequency characteristics of the interpolation filter 2.

[0004]

However, in the above-described conventional configuration, the R, G, and B signals forming the color difference signal generated by the color signal phase compensation circuit have the same temporal phase, but the frequency characteristics are It does not match. The R, G, and B signals are generally passed through an optical low-pass filter before being input to the color signal phase compensation circuit to limit the frequency band.
Since the signal of No. 2 further passes through the interpolation filter, it does not match the frequency characteristics of the G signal, and there is a problem that the frequency characteristics of the signals of the three channels of R, G, B differ.

The present invention solves the above-mentioned problems of the prior art, and is a color signal phase for producing two color difference signals from R, G, and B signals whose temporal phases match and whose frequency characteristics almost match. It is intended to provide a compensation circuit.

[0006]

In order to achieve this object, a color signal phase compensating circuit of the present invention uses the G signal (or R signal and B signal) as the temporal phase of the R signal and B signal (or G signal). An interpolation filter for matching the temporal phase of the signal) and the low-frequency characteristics of the G signal (or R signal and B signal) to the low-frequency characteristics of the R signal and B signal (or G signal) And a circuit for generating two color difference signals from the output signal of the interpolation filter and the output signal of the low pass filter.

[0007]

According to the present invention, the G signal is converted into the R and B signals by the above structure.
The signal is input to the delay unit via a low-pass filter that matches the spatial phase of the signal and the frequency characteristic of the low frequency band, is delay-compensated, and is output to the subtractor at a double sampling frequency rate.

With the above operation, the frequency characteristic of the G signal is almost the same as the frequency characteristic of the R and B signals in the low range in the state where the temporal phases of the R, G and B signals are matched by the low pass filter. Can be matched.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a consumer use 3 according to an embodiment of the present invention.
It is a block diagram of a color signal phase compensation circuit of the plate video camera. In FIG. 1, 1 is a conversion unit that time-divisionally outputs R and B signals and outputs at a double sampling frequency rate, and 2 is an interpolation filter that receives the output signal of the conversion unit 1 and has a characteristic of 1 + Z ^-2 , 5 inputs the G signal and 1+
6Z ^-1 + Z ^-2 low-pass filter, 3 delays the output signal of the low-pass filter 5 and outputs at a double sampling frequency, 4 delay signal of the delay unit 3 and output of the interpolation filter 2 Signal to RG signal and B
-A subtractor for generating the G signal.

The operation of the color signal phase compensating circuit of the consumer-use three-plate video camera of the present embodiment constructed as described above will be described below. Although the R, G, and B signals are input, since the spatial pixel shift method is usually used to prevent the occurrence of moire, the G solid-state image sensor is horizontally arranged with respect to the R and B solid-state image sensors. Shifted by half a pixel. R and B
Signal is first time-divided by the conversion unit 1, and time-division R and B signals are output at a rate of twice the sampling frequency. The conversion unit 1 has the same configuration as that of the conventional example, and includes a D-type flip-flop 1 that latches a signal at a sampling frequency as shown in FIG. 4, and a selector 2 that selects one of the R signal and the B signal using the sampling clock as a control signal. ,
It is composed of a D-type flip-flop 3 that latches a signal at twice the sampling frequency. The output signal of the conversion unit 1 is input to the interpolation filter 2, but this circuit adopts the configuration of the low-pass filter 5 having the characteristic of 1 + Z ^-2 as in the conventional example. On the other hand, the G signal is input to the low-pass filter 5 at the sampling frequency rate, and the frequency characteristics are made to substantially match the frequency characteristics of the R and B signals in the low range without changing the temporal phase. Low-pass filter 5 of this embodiment
Has a characteristic of 1 + 6Z ^-1 + Z ^-2 , and a G signal, a signal obtained by multiplying the gain of a signal that has passed through one D-type flip-flop that latches the G signal by 6 times, and a D-type flip-flop that latches the G signal are The addition result of the two passed signals is output. The frequency characteristic of the interpolation filter 2 having a characteristic of 1 + Z ^-2 in FIG. 5 shows the frequency characteristic of the low-pass filter 5 having the characteristic of 1 + 6Z ^-1 + Z ^-2 in FIG. As is apparent from FIGS. 2 and 5, the frequency characteristics of both are the color subcarrier frequencies 3.
It is almost the same in the low frequency range below 58 MHz. The output signal of the low-pass filter 5 is input to the delay unit 3, adjusted so that the R and B time-division signals of the output of the interpolation filter 2 and the gain and delay are matched, and output at a double sampling frequency rate. .. The subtractor 4 outputs the G signal which is the output signal of the delay unit 3 and the two time-division color difference signals R and B which are the output signals of the interpolation filter 2 from the time-division R and B signals.
Generates G and B signals.

As described above, according to this embodiment, 1 + 6Z
^{By the} low-pass filter having the characteristic of ^-1 + Z ^-2 , the frequency characteristic can be almost matched with the frequency characteristic of the R and B signals in the low frequency range without changing the temporal phase of the G signal, and the spatial pixel shift is performed. It is useful as a color signal phase compensating circuit for a consumer-use three-plate video camera using the method.

Further, the G signal channel is provided with an interpolation filter for matching the temporal phase with the R and B signals,
A configuration may be adopted in which the channels of the R and B signals are provided with a low-pass filter for matching the low frequency characteristic of the G signal with the low frequency characteristic of the G signal.

[0014]

As described above, according to the present invention, time sharing R and B are performed.
The signal channel is equipped with an interpolation filter having a characteristic of 1 + Z ^-2 , the channel of the G signal is provided with a low-pass filter having a characteristic of 1 + 6Z ^-1 + Z ^-2 , and the G signal is delayed and output at a double sampling frequency rate. By providing the delay unit, the time phases of the R, G, and B signals can be matched, and the frequency characteristics of the G signal can be substantially matched with the frequency characteristics of the R and B signals in the low range.
Its practical effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a color signal phase compensation circuit according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing frequency characteristics of a low pass filter 5 in the same embodiment.

FIG. 3 is a block diagram showing a configuration of a conventional color signal phase compensation circuit.

FIG. 4 is a block diagram showing an example of a circuit configuration of a conversion unit 1 in FIGS. 1 and 3.

FIG. 5 is a characteristic diagram showing frequency characteristics of the interpolation filter 2 in FIGS. 1 and 3.

[Explanation of symbols]

 1 conversion unit 2 interpolation filter 3 delay unit 4 subtractor 5 low-pass filter

Claims (1)

[Claims] 1. A digital signal processing for color of a three-plate video camera using a spatial pixel shift method in which a green solid-state image sensor is horizontally shifted by a half pixel compared to red and blue solid-state image sensors and arranged in a prism. And an interpolation filter for matching the temporal phase of the red and blue digital video signals (or the green digital video signal) with the temporal phase of the green digital video signals (or the red and blue digital video signals). Adjusting the low-frequency characteristics of the green digital video signal (or the red and blue digital video signals) to the low-frequency characteristics of the red and blue digital video signals (or the green digital video signals) And a circuit for generating two color difference signals from the output signal of the interpolation filter and the output signal of the low pass filter. And a color signal phase compensation circuit characterized by: