JPS5834069B2 - Single-tube frequency-separated color television camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single-tube frequency-separated color television camera in which a color signal and a luminance signal are frequency-multiplexed and output from a single image pickup tube.

Various types of color television cameras, such as single-carrier type and dual-carrier type, have been proposed in relation to the configuration of the stripe filter used in the color television camera mentioned above. Since signals and color signals are obtained at the same time, improving the S/N ratio and resolution of color signals at the same time is a problem that is difficult to solve easily. This is the current situation.

However, the present invention reduces the false color signals mixed in the modulated color signal by devising the configuration of the stripe filter, the selection of the spatial frequency filter, and the configuration of the luminance and color separation circuits based on them. In addition to improving the /N ratio, the frequency band of the luminance signal is substantially expanded to improve resolution.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 1 shows the configuration of a stripe filter used in the color television camera of the present invention, showing an angle θ1 with respect to a virtual reference line l perpendicular to each horizontal scanning line of the electron beam of the image pickup tube.
A first stripe filter S1 consisting of periodic repetitions of transparent T and cyan C with a width d1 inclined by , and an angle θ2 in the opposite direction to the first stripe filter S1 with respect to the virtual reference line l. a second stripe filter S2 consisting of a periodic repetition of transparent T and yellow Y having a width d2 inclined by , and each filter S1
．． In such a way that the phase of each of the red and blue modulated color signals modulated and derived in S2 is reversed for each horizontal scanning period of the image pickup tube, the phase of each stripe is matched with the two adjacent horizontal scanning lines (L) of the image pickup tube. ) (Ln+1) (Ln+2) . . .

FIG. 2 shows a schematic configuration of a color television camera of the present invention using such a color separation filter, and numeral 1 indicates each of the above-mentioned stripe filters provided in close contact with the photocathode of the image pickup tube 2.

This first and second stripe filter S1. S2 is determined by the stripe width in the horizontal scanning direction of the image pickup tube and the horizontal scanning frequency of the image pickup tube, and the former color carrier frequency f1. f2 is selected to be relatively low at 3, 5 MHz, and 4.5 MHz, respectively, so that the S/N of the color signal depends on the attenuation of the high-frequency characteristics of the image pickup tube.
The structure is configured to suppress a decrease in the ratio.

A spatial frequency filter 4 is disposed in the optical path between the color separation filter 1 and the ticking lens 3.8 This filter 4 has spectral selectivity, and for light of the former color, the spatial frequency is changed to the color of the red light. Carrier frequency f1. The lower frequency f of f2 is limited to the following, but the spatial frequency is not limited for green light.

5 is a preamplifier circuit whose input is the output of the image pickup tube 2;
6 is the color carrier frequency f1. a first bandpass filter circuit whose passbands are both bands of the red and blue modulated color signals, each using f2 as a carrier wave; 7 an IH delay circuit that delays the output by an IH period corresponding to one horizontal scan of the image pickup tube 2; 8; 9 is a subtraction circuit that subtracts the output from the first bandpass filter circuit 6;
10 is a second and third bandpass filter circuit whose pass band is the red and former modulated color signal bands; 11 and 12 are red and blue demodulation circuits that demodulate the low-frequency red and former color signals from their respective outputs; 13 is a correction delay circuit for correcting the phase difference between the output of the preamplifier circuit 5 and the output of the first bandpass filter circuit 6; 14 is an adder circuit for adding the output and the output of the IH delay circuit 7; 15; 1 is a low-pass filter circuit whose passband substantially coincides with the passband of the spatial frequency filter 4 for red, the former color light;
6 is the red and blue demodulation circuits 11 and 12, the addition circuit 14,
and a color NTSC encoder which obtains each output of the low-pass filter circuit 15 and creates a color NTSC signal.

In the color television camera having such a configuration, the output of the first bandpass filter circuit 6 includes first and second stripe filters S1 . S
There are red and blue modulated color signals by 2 and high-frequency components of a green signal whose spatial frequency is not limited by the spatial frequency filter 4. In the horizontal scanning period 2H, the tilt is also inverted in phase, but the green signal component appears in the same phase, and since the video information of these adjacent 2Hs is extremely similar, the first
If the output of the bandpass filter circuit 6 is subtracted between each adjacent 2H, the green signal component is canceled and only the red and blue modulated color signals are taken out from the subtraction circuit 8.
The signals are separated by the third bandpass filter circuit 9 and 10 and demodulated into low-frequency blue and red color signals R and B.

- After the phase difference between the output of the preamplifier circuit 5 and the output of the first band filter circuit 6 is corrected by the correction delay circuit 13, the output of the preamplifier circuit 5 is added to the output of the first band filter circuit 7 via the IH delay circuit 7. For example, the red and blue modulated color signals in the two outputs whose phase difference is inverted between adjacent 2Hs cancel each other out, and the brightness signal Y containing the high frequency component of the green signal that always appears in the same phase is taken out from the adder circuit 14. .

This luminance signal Y is taken out from the output of the preamplifier circuit 5 by a low-pass filter circuit 15, and is wideband by the high frequency of the green signal compared to the low frequency luminance signal YL including low frequency red, blue, and relative signals. This means that

Therefore, the color NTSC encoder 16
'When obtaining the SC signal, the narrowband luminance signal YL is
Together with the former signals R and B, it is used to obtain a low-band green signal G, and on the other hand, the broadband luminance signal Y is used together with the red, blue, and related signals R2B and G to obtain each color difference signal. (RY) (B
-Y ) (G-Y), a high-resolution color NTSC signal can be obtained.

According to the color television camera of the present invention, by using a spatial frequency filter having spectral selectivity in combination with a specially configured stripe filter, it is not modulated by the stripe filter and is not subjected to frequency limitation by the spatial frequency filter. The high-frequency component of the green signal is derived during the image pickup tube output, and the correlation between the high-frequency component of the green signal and the red and blue modulated color signals in adjacent horizontal scanning periods of the image pickup tube output is calculated. Since the luminance signal containing the high-frequency components of the separated green signal is used as the luminance signal when obtaining a color television signal, the spatial frequency is adjusted to prevent the generation of false color signals. Even if the spatial frequency of the red and former color lights is limited by a filter, the luminance signal can be kept in a substantially wide band, so there is no risk of deterioration in resolution. Since the separation is based on the correlation between scanning lines and so-called frequency separation, the luminance and color separation circuit has a particularly complicated configuration even if it obtains a luminance signal including the high frequency component of the green signal as described above. This is an effective single-tube frequency-separated color television camera.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a stripe filter used in the present invention, and FIG. 2 is a block diagram showing the schematic configuration of the color television camera of the present invention. 1... Stripe filter, 2... Image pickup tube, 4... Spatial frequency filter, 6, 9.1
0...Band filter circuit, 7...IH delay circuit, 8...Subtraction circuit, 11.12...
- Color demodulation circuit, 14... Addition circuit.

Claims (1)

[Claims] 1 Two types of stripe filters with different stripe widths are tilted in opposite directions with respect to a virtual reference line perpendicular to each horizontal scanning line so that the phase of each stripe is reversed for each horizontal scanning line of the image pickup tube. In addition, a spatial frequency filter is provided in front of each of the stripe filters to limit the high spatial frequency of the red and former color light modulated by each of the stripe filters. By adding and subtracting the tube output in two adjacent horizontal scanning periods, the red and blue modulated color signals from the image pickup tube output are not modulated by the stripe filter, and the spatial frequency is limited by the spatial frequency filter. A color television signal is obtained by separating a luminance signal containing high-frequency components of a green signal that is not received, and by using the separated luminance signal and a red signal and a blue signal that are separated and demodulated from the red and blue modulated color signals. Tube frequency separation type color television camera.