JPH0418511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving color saturation in a beam-indexed color receiver.

As shown in FIG. 4, a beam index type color receiver is constructed by repeatedly coating the inner surface of a face plate with red, green, and blue phosphor strips G, R, and B with a non-luminescent substance 11 interposed therebetween to create a phosphorescent surface. The index phosphor strips 11 are coated at pitches that have a fixed relationship with the pitches of a set of three primary color phosphor strips (referred to as one triplet) on the phosphor surface. When this fluorescent surface is scanned with a single electron beam, the index phosphor is stimulated to emit light, and by detecting this emission, an index signal is obtained, and the precise scanning position of the single electron beam on the fluorescent surface can be determined. is detected, and this signal is used to switch the three primary color signals. The drive signal for the cathode ray tube is expressed as Em+Ec cos(ω _T t+φ).
However, Em is the luminance signal, Ec is the color saturation signal,
ω _T is the angular velocity for color generation, and φ is the color phase signal.

For example, when the beam strikes the red phosphor strip R on the phosphor surface and reproduces red color, the distribution of the electron beam is shown as a broken line in contrast to the driving voltage waveform shown as a solid line as shown in Figure 4. Due to the distribution shown in , the beam spreads and overlaps the phosphors B and G other than red, causing the phosphors B and G to emit light, albeit slightly.

For this reason, the saturation level of red decreases. The reason why the red saturation level decreases is that the beam spot diameter inevitably increases as the beam amount increases. FIG. 3 shows the relationship between beam current and spot diameter, with the vertical axis having the width d of one phosphor stripe as a unit.

Even if Ec is increased to reproduce highly saturated colors, if the diameter of the spot where the beam intensity is maximum is three times (3d) or more the width of the phosphor stripe, the beam spot will be overtaken by other fluorescers. It spreads to the striae of the body and actually reduces the saturation of the reproduced color.

In order to reduce the decrease in saturation due to an increase in the beam spot diameter, it is possible to reduce the decrease in color saturation by constantly lowering the luminance signal, which is the DC bias of the drive signal, by a certain value. However, as a result, the entire screen becomes darker by the amount that the DC bias is lowered, and if the DC bias is lowered too much, there is a problem in that index detection errors occur in dark parts of the reproduced image.

The present invention reduces the decrease in color saturation due to an increase in the beam spot diameter without changing the brightness of the screen.

The configuration of the present invention is shown in FIG. As is known in a known beam index color receiver, a cathode ray tube 1 is provided with a photodetector 2 for detecting an optical index signal, and the detected signal is processed by an index signal processing circuit 3 to produce a signal at the truplet frequency. Create cos ω _T t. Next, the mixer circuit 4 generates the triplet frequency signal cos ω _T t
and the color carrier wave cos ωt to obtain a signal with the frequency sum component cos(ω _T +ω)t. This signal and the color signal for the index method Ec cos (ωt + φ)
are added in mixing circuit 5, and the frequency component of the difference is
Extract only Ec cos(ω _T t+φ). This signal and a signal Em−, which will be described later, is obtained by processing the luminance signal Em.
aEc and is synthesized by the synthesis circuit 6, and the drive signal E=Em
−aEc+Ec cos(ω _T +φ) and drives the cathode ray tube.

The feature of the present invention is that the brightness signal Em, which is a direct current component, of the drive signal of the cathode ray tube is converted into an amount proportional to the saturation degree Ec.
Lower the DC bias of the drive signal by aEc and Em−
The reason is that it is aEc. Only when reproducing color, the DC bias is reduced by an amount proportional to the saturation of the color, so that the spot diameter at the point of maximum beam intensity is more than three times the width of the phosphor strip G. , B to prevent it from spreading. In the present invention, the DC component changes in proportion to the color saturation signal Ec and is controlled only during color reproduction, so it is possible to reduce the decrease in color saturation of the fluorescent surface without changing the brightness of the screen. It can be done. Also, color saturation signal
Since Ec can be made larger than in conventional methods, bright colors with high saturation can be reproduced even if the maximum beam amount remains the same.

In order to create the DC bias Em-aEc in which the luminance signal Em is corrected by the color saturation signal, various circuit configurations can be considered, and the one shown in FIG. 1 is one example. The color signal Ec cos(ωt
+φ) is applied to detect the color saturation signal Ec. This signal Ec is applied to a gain adjuster 8 to produce a corrected signal -aEc of an appropriate magnitude, which is combined with the luminance signal Em in a synthesizer 9 to form Em-aEc.

According to the present invention, the luminance signal Em is determined by the color saturation signal Ec.
Since the brightness of the screen does not decrease, the beam spot diameter remains unchanged even at maximum color saturation.
It has an excellent effect of preventing a decrease in the color saturation of the fluorescent surface by keeping it below 3D.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the configuration of the present invention, Figure 2 is an explanatory diagram showing the voltage waveform on the fluorescent surface and the beam spot diameter in the present invention, and Figure 3 is the relationship between the beam current and the spot diameter. 4 are explanatory diagrams showing the driving voltage waveform and beam spot diameter in a conventional index color receiver. 1...Cathode ray tube, 2...Photodetector, Em...Luminance signal, Ec...Color saturation signal, _ωT ...Angular frequency for color generation, φ...Color phase.

Claims (1)

[Claims] 1. In a beam index type color receiver, an envelope detector 7 that processes a color signal and detects a color saturation signal E _c , and the magnitude of this color saturation signal E _c a gain adjuster 8 for forming a modified signal -aE _c proportional to the luminance signal E _n and a first synthesizer 9 for outputting a modified luminance signal E _n -aE _c based on the luminance signal E _n and the correction signal -aE c; A beam index type color receiver, comprising: a second combiner 6 for controlling a DC via of a drive signal for driving a drive signal using the modified luminance signal E _n -aE _c .