Apparatus for processing a component video signal having a wideband luminance component

Abstract: In apparatus for recording/reproducing a component video signal having a luminance signal (S YH ) of a wide frequency band so as to be reproducible to provide a picture of high resolution and a chroma signal (S CL ) in a chroma band included in the frequency band of the luminance signal (S YH ) substantially below the high end of the latter, a recording signal processing circuit (20) separates (21,10) from the luminance signal (S YH ) a slant direction luminance signal (S HY ) in a frequency band that includes and extends substantially above the chroma band, whereupon the luminance signal (S YH ) is suppressed (12) by the slant direction luminance signal (S HY ), and a component of the slant direction luminance signal (S HY ) in the chroma band is frequency-­ converted (23,25,26) to a higher band and is frequency interleaved with the suppressed luminance signal (S YK ). The chroma signal (S CL ) is frequency interleaved (9) with the suppressed luminance signal (S YK ) and is then added (13,29) to the latter and to the frequency-converted slant direction luminance signal (S LY ) to form the video signal (S ADD1 ) which is to be recorded. In the reproducing mode, a circuit (40) for processing the reproduced video signal separates (6,7,41-45) therefrom the chroma signal (S CK ), the frequency-converted slant direction luminance signal (S LY ) and the suppressed luminance signal (S YK ), whereupon the separated frequency converted slant direction luminance signal (S LY ) is frequency-reconverted (47,49) back to the chroma band and into frequency interleaved relation with the suppressed luminance signal (S YK ), and the reconverted slant direction luminance signal (S SI ) and the separated suppressed luminance signal (S YK ) are added (51) to provide a luminance signal (S SHO ) which, with the separated chroma signal (S CK ), forms a reproduced component video signal.

Description: This invention relates to video systems and, more particularly, is directed to circuits for processing video signals during recording and/or reproduction, as in a video disc player. It is known for a standard video signal, for example, according to the NTSC system, and which will be hereinafter referred to as a composite video signal, to be frequency modulated and then recorded on a video disc. As shown in Figure 1 of the accompanying drawings, in a video disc player 1 for reproducing such a standard video signal recorded on a video disc, an optical pick-up (not shown) reproduces the frequency-modulated composite video signal which is then frequency-demodulated in a circuit 4. A component of the demodulated composite video signal S STV situated in a chroma band is then extracted from the demodulated composite video signal by a bandpass filter circuit 5, and the resulting extracted signal component is processed by a comb-type filter circuit 6 to provide a chroma signal S C separated from the composite video signal. Further, the separated chroma signal S C is subtracted from the composite video signal S STV in a subtracting circuit 7 which thereby provides a separated luminance signal S Y . In a video apparatus, such as a camera or image pick-up apparatus or the like, an image signal is frequently not converted to a composite video signal, but rather is output as a component video signal, that is as separated luminance and chrominance signals. In the case of a component video signal, as contrasted with the usual composite video signal, a luminance signal of wide frequency band can be provided for obtaining a displayed picture therefrom of high resolution. In other words, if a component video signal including a luminance signal of wide frequency band is recorded on a video disc, then a picture of high resolution or image quality may be reproduced by a video disc player. However, when recording a component video signal including a luminance signal of wide frequency band on a video disc, it is necessary to establish compatibility between such a high resolution video disc and a conventional video disc on which a composite video signal is recorded. To this end, it has been proposed that, as shown in Figure 2 of the accompanying drawings, a luminance signal S YH of wide frequency band and a chroma signal S CH , which form a component video signal, be added by an adding circuit 8 so as to provide a signal S REC which is then recorded on the video disc. When such a simple proposal is followed, interference between the luminance signal S YH and the chroma signal S CH cannot be avoided so that problems such as cross-colour, dot interference and the like occur and the quality of the resulting displayed picture is degraded. In order to solve the foregoing problems, it has been proposed, for example, as shown in Figure 3 of the accompanying drawings, to superimpose a chroma signal S CL upon a relatively wide band luminance signal S YH through the use of comb-type filter circuits 9 and 10. More specifically, the chroma signal S CL , which is initially limited to a band similar to the frequency band of the chroma in the standard composite video signal, is fed to the comb-type filter circuit 9 in which signal components having frequencies (n-1) f H , nf H , (n+1) f H , ... are suppressed so as to provide a chroma signal S CK having a comb-like frequency characteristic as shown in full lines in Figure 4 of the accompanying drawings, and wherein f H represents the horizontal synchronising frequency. The wide band luminance signal S YH is supplied to a band-pass filter circuit 11 which has a pass-band equal to the frequency band of the chroma signal S CL , and which is hereinafter referred to as the "chroma band". The component of the luminance signal S YH in the chroma band, that is the component of the luminance signal S YH passing through the band-pass filter circuit 11, is supplied to the comb-type filter circuit 10 which has the same characteristic as the comb-type filter circuit 9. A subtracting circuit 12 subtracts the output of the comb-type filter circuit 10 from the luminance signal S YH , and thereby suppresses a signal component of the frequencies (n-1/2) f H (n+1/2) f H ... within the chroma band of the luminance signal S YH . Therefore, at the output of the subtracting circuit 12, there is obtained a luminance signal S YK which is frequency-interleaved with respect to the chroma signal S CK , and which is represented by the dotted line in Figure 4. When the luminance signal S YK and the chroma signal S CK are added in an adding circuit 13, there is obtained, as the output from the adding circuit 13, a video signal S ADD having a frequency characteristic corresponding to that of the standard composite video signal in the frequency band below the chroma band, and which contains luminance information in a frequency band above the chroma band. Since the previously-proposed video disc player 1 (Figure 1) is arranged to process the signal component in the band lower than the chroma band, such a player can be used for playback of a video disc on which the video signal S ADD has been recorded rather than the standard or conventional composite video signal S STV (Figure 1). Thus, deterioration of the quality of the displayed picture can be avoided and the compatibility of a video disc recorded with the video signal S ADD , that is a signal which includes a wide band luminance signal, with the previously-proposed video disc player 1 can be established. Further, if the video disc recorded with the video signal S ADD is reproduced on a video disc player intended for exclusive use therewith so as to reproduce luminance information in the frequency band higher than the chroma band, it is possible to improve the resolution of the resulting displayed picture, as compared with the picture obtained from the standard composite video signal. However, in the signal processing operation described above with reference to Figure 3, a signal component of the luminance signal S YK is suppressed by the operation of the bandpass filter 11, the comb-type filter circuit 10 and the subtracting circuit 12 so that the luminance signal S YK is frequency-interleaved with the chroma signal S CK in the signal S ADD . Therefore, luminance information in the oblique or slant spectral portion is dropped-out of the video signal S ADD within the chroma band. As a result, even though the luminance signal is extended into a high frequency band, the visual resolution of the displayed picture will not be greatly enhanced. In other words, although a component video signal including a wide band luminance signal is recorded, it is difficult to obtain a picture whose image quality is improved to the extent that would be realised by effectively utilising the characteristics of the component video signal. In JP-A-56 119593, there is disclosed a circuit for modifying a composite colour video signal into a format resulting in reduced vertical resolution picture degradation. The frequency band of the chroma component of the original video signal is centred around the upper limit of the luminance spectrum. In the modified signal, the composite signal is suppressed by forming notches in the upper part of the luminance spectrum; the luminance part of this suppressed signal is frequency-converted to interleave with the upper part of the notched spectrum, and the chroma part is frequency-converted to interleave with the lower part of the notched spectrum. According to one aspect of the invention there is provided a signal processing circuit for an apparatus for recording or transmitting a component video signal having a wide frequency band luminance signal so as to be reproducible or receivable to obtain a picture of high resolution and a chroma signal in a chroma band included within said frequency band of the luminance signal and being substantially below the high end thereof, the signal processing circuit comprising: means receiving said luminance signal for separating therefrom an intermediate luminance signal with a frequency band spectrum extending from the lower band limit of said chroma band to the upper end of the luminance spectrum and having notches at uniform frequency intervals, and for suppressing said luminance signal by said intermediate luminance signal so as to obtain a suppressed luminance signal such that, in its spectrum, for a frequency band extending from the lower band limit of said chroma band to the upper end of the luminance spectrum, notches are formed at said uniform frequency intervals; frequency-converting means for frequency-converting a spectral portion of said intermediate luminance signal in said chroma band to a frequency-converted intermediate luminance signal which is frequency interleavable with said suppressed luminance signal and which is in a frequency band higher than said chroma band; means for generating from said chroma signal a modified chroma signal at the same spectral position as said first-mentioned chroma signal and which is modified to be frequency-interleavable at the notches of the notched frequency band of said suppressed luminance signal; and means for adding said suppressed luminance signal, said frequency-converted intermediate luminance signal and said modified chroma signal so as to provide an added signal to be recorded or transmitted. According to another aspect of the invention there is provided a circuit for processing a recorded or transmitted video signal for an apparatus for reproducing or receiving the recorded or transmitted video signal, the video signal being of the form of the added signal as set out above and thereby composed of the suppressed luminance signal frequency interleaved with the modified chroma signal and also with the frequency-converted intermediate luminance signal in the frequency band higher than the chroma band, the processing circuit comprising: separating means receiving the reproduced or received video signal for separating therefrom said modified chroma signal, said frequency-converted intermediate luminance signal and said suppressed luminance signal; frequency-converting means for reconverting the separated frequency-converted intermediate luminance signal to said chroma band and in frequency interleaved relation to said suppressed luminance signal; and adding means for adding the reconverted intermediate luminance signal and the separated suppressed luminance signal so as to provide therefrom a luminance signal in which oblique spectrum luminance information is dropped-out in notches only in a frequency band above said chroma band and which forms, with the separated chroma signal, a component video signal. A preferred embodiment of the invention described below provides a video signal processing apparatus which can eliminate the above-noted problems associated with the previous proposals. More specifically, the preferred embodiment provides a component video signal processing apparatus for use in recording and/or reproducing a video signal, for example, on a video disc, and by which a visual image of high quality can be reproduced while maintaining compatibility of the resulting video disc with video disc players intended for the playback of a standard composite video signal. The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 is a block diagram showing a reproduced signal processing circuit of a previously-proposed video disc player; Figures 2 and 3 are block diagrams showing respective previously-proposed circuits for processing a component video signal composed of separately-received luminance and chroma signals in preparation for recording thereof; Figure 4 is a diagram showing frequency spectra to which reference will be made in explaining the operation of the signal processing circuit of Figure 3; Figure 5 is a block diagram of a signal processing circuit according to an embodiment of this invention, and which is used in recording a component video signal having a wide band luminance signal; Figures 6A to 6H are diagrams showing frequency spectra to which reference will be made in explaining the operation of the circuit of Figure 5 in processing a component video signal to be recorded; and Figure 7 is a block diagram showing a signal processing circuit according to an embodiment of this invention for use in a playback operation of a video disc player which can be used either with a standard video disc recorded with a composite video signal or with a video disc recorded with a component video signal having a wide band luminance signal and which is recorded after processing by the circuit of Figure 5. Referring to the drawings in detail, and initially to Figure 5 thereof in which parts corresponding to those described above with reference to Figure 3 are identified by the same reference numerals and letters, it will be seen that, in a circuit 20 according to an embodiment of the present invention for processing a component video signal prior to its recording on a video disc (not shown), a luminance signal S YH (Figure 6A) having a wide frequency band, for example extending to 7 MHz, is supplied to a high-pass filter circuit (HPF) 21. The frequency of 7 MHz at the upper end of the frequency band of the luminance signal S YH is the maximum frequency that can be recorded on or reproduced from a video disc. The HPF 21 has a cut-off frequency substantially corresponding to the frequency at the low end of the frequency band of the chroma signal S CL of the component video signal to be recorded. Thus, the HPF 21 extracts from the luminance signal S YH a signal component S S (Figure 6B) which includes the frequencies of the chroma band and extends thereabove to the upper end of the wide band luminance signal. This component S S of the luminance signal S YH is supplied to a comb-type filter circuit 10 which has a comb-tooth characteristic similar to that of the comb-type filter circuit 10 of Figure 3, and in which the level of the signal component S S is suppressed at frequencies spaced apart by f H so as to provide a signal S HY (Figure 6D) hereinafter referred to as a slant direction or intermediate luminance signal. The chroma signal S CL of the component video signal supplied to the processing circuit of Figure 5 is applied to a further comb-type filter circuit 9 having a comb-tooth characteristic similar to that of the comb-type filter circuit 10 so that the chroma signal S CK at the output of the filter circuit 9 has the characteristic shown in Figure 6C. The intermediate luminance signal S HY derived from the comb-type filter circuit 10 is subtracted from the wide band luminance signal S YH in a subtracting circuit 12 so that the luminance signal S YH is suppressed by the intermediate luminance signal S HY over the frequency band of the latter. In other words, the suppressed luminance signal S YK (Figure 6E) obtained at the output of the subtracting circuit 12 is suppressed so as to be in frequency-interleaved relation with the chroma signal S CK obtained from the comb-type filter circuit 9. It will be appreciated that, in the circuit arrangement as described above with reference to Figure 5, the wide band luminance signal S YH is separated to provide a signal component, that is the intermediate luminance signal S HY , having a frequency band extending from the lower end of the chroma band substantially to the upper end of the band of the luminance signal S YH , that is to a frequency substantially higher than the upper end of the chroma band, and which contains the luminance information in the slant spectral portion, and also to provide a signal component, that is the suppressed luminance signal S YK , having a frequency band corresponding to that of the wide band luminance signal S YH so as to extend substantially above the chroma band, but which has no luminance information in the slant spectral portion over the range of frequencies corresponding to the chroma band and thereabove to the high end of the frequency band of the luminance signal S YH . It will further be appreciated that, in the suppressed luminance signal S YK (Figure 6E), all of the luminance information is retained in the frequency band below the chroma band as in a composite video signal. Referring again to the signal processing circuit 20 of Figure 5, it will be seen that the intermediate luminance signal S HY is also applied to a low-pass filter circuit (LPF) 23 having a cut-off frequency substantially at the upper end of the chroma band so as to extract from the signal S HY a signal component S SI (Figure 6F) having a frequency band substantially equal to that of the chroma band, and which is hereinafter referred to as a low frequency portion of the intermediate luminance signal. This low frequency portion S SI is supplied to a multiplier circuit 25 in which it is multiplied by a reference signal S OSC which, for example, has a frequency of 534 f H . The output of the multiplier circuit 25 is supplied to a further low-pass filter circuit 26 having a cut-off frequency at the upper end of the wide band luminance signal S YH , for example, a cut-off frequency of 7 MHz. The multiplier circuit 25 and the LPF 26 cooperate to provide, at the output of the LPF 26, a frequency-converted intermediate luminance signal S LY (Figure 6G) in a frequency band higher than the chroma band which is situated between the cut-off frequencies of the HPF 21 and the LPF 23. By selecting the frequency of the reference signal S OSC to be 534 f H , the low frequency portion of the intermediate luminance signal S SI having frequencies lower than the central frequency thereof is frequency-converted so as to correspond to the component of the frequency-converted intermediate luminance signal S LY having frequencies higher than the central frequency of the latter. Thus, as is apparent from a comparison between Figures 6F and 6G, the signal level of the frequency-converted intermediate luminance signal S LY in the lower frequency portion thereof is lower than the level of the signal S LY in the higher frequency portion of the latter. Further, by selecting the frequency of the reference signal S OSC to be 534 f H , the frequency-converted intermediate luminance signal S LY has a comb-like frequency characteristic in which the signal level is suppressed at frequencies based on nf H and which are spaced apart by the frequency f H , similarly to the chroma signal S CK . Consequently, the frequency-converted intermediate luminance signal S LY is frequency-interleaved with the suppressed luminance signal S YK derived from the subtracting circuit 12. Therefore, when the suppressed luminance signal S YK and the frequency-converted intermediate luminance signal S LY are added by an adding circuit 29, the resulting mixed luminance signal S GO obtained from the output of the adding circuit 29 has a frequency characteristic which is the same as that of the standard composite video signal in the frequency band below the upper end of the chroma band. It will be seen that the mixed luminance signal S GO includes, in the frequency band lower than the chroma band, luminance information in the lateral direction and in the slant direction of the suppressed luminance signal S YK , and luminance information in the slant spectral portion for frequencies in the chroma band and also in the lateral direction for frequencies higher than the chroma band and which are contributed by the frequency converted intermediate luminance signal S LY and the suppressed luminance signal S YK , respectively. As described above, in the present embodiment, the luminance information in the chroma band is frequency-converted to a relatively higher band, for example, as in the frequency-converted intermediate luminance signal S LY , so that the luminance information suppressed or dropped-out of the suppressed luminance signal in the chroma band in order to maintain compatibility with the standard composite video signal is converted to a frequency band above the chroma band, so as to be recordable on a video disc in which a component video signal having its luminance signal band up to 7 MHz is to be recorded. It is known that luminance information having a low frequency can be visually sensed more easily than luminance information having a higher frequency. The present technique takes advantage of the foregoing phenomenon by retaining the slant direction luminance information for the chroma band, which is relatively low, and frequency-converting the corresponding low frequency portion of the intermediate luminance signal S SI so as to form the frequency-converted intermediate luminance signal S LY which is recorded in place of the intermediate luminance information in the frequency band higher than the chroma band. By reason of the foregoing, when a component video signal recorded with a wide-band luminance signal in accordance with the present technique is reproduced, the resolution of the resulting picture can be improved to the full extent that is possible by reason of the increased frequency band that can be recorded and reproduced on the video disc. After the frequency-converted intermediate luminance signal S LY and the suppressed luminance signal S YK have been added together in the adding circuit 29, the resulting mixed luminance signal S GO is added to the chroma signal S CK in the adding circuit 13 so as to provide an added signal S ADD1 (Figure 6H). Then, the added signal S ADD1 is supplied to a frequency modulating circuit 30 and the resulting frequency modulated signal is supplied to a recording circuit (not shown) by which the signal is recorded on a mother disc or the like. When the mixed luminance signal S GO is added to the chroma signal S CK in the adding circuit 13, the signal level of the frequency-converted intermediate luminance signal S LY , at its relatively lower frequency portion, is relatively low so as to avoid mutual interference with the adjacent added chroma signal S CK and thereby permit a video signal of enhanced image quality to be obtained. It will be apparent that a mother disc produced as described above can be conventionally duplicated to provide so-called high-resolution video discs therefrom which, when used with a corresponding video disc player designed to take advantage of its high-resolution qualities, can make possible the display of a picture of high image quality, while being compatible with conventional video disc players, that is, those intended for use with video discs recorded with a composite video signal. When a high-resolution video disc recorded with the added signal S ADD1 according to this technique is used with a conventional video disc player, the frequency band above the chroma band is not reproduced so that the frequency-converted slant direction luminance signal S LY is omitted from the reproduced video signal which is thereby made similar to a reproduced composite video signal. In the embodiment described above with reference to Figure 5, it will be seen that the comb-type filter circuit 10, the subtracting circuit 12 and the HPF 21 constitute separating means for separating the luminance signal S YH into the intermediate luminance signal S HY formed of oblique spectrum luminance information in a frequency band that includes and extends substantially above the chroma band, and into the suppressed luminance signal S YK which results from subtracting the slant direction luminance signal S HY from the luminance signal S YH . The LPFs 23 and 26 and the multiplier circuit 25 constitute frequency-converting means by which a component of the intermediate luminance signal S HY limited to the chroma band is frequency converted to a frequency band higher than the chroma band and is frequency-interleaved with the suppressed luminance signal S YK . Finally, in the embodiment of Figure 5, the adding circuits 13 and 29 constitute adding means for adding together the suppressed luminance signal S YK , the frequency-converted intermediate luminance signal S LY and the chroma signal S CK frequency-interleaved with the suppressed luminance signal S YK , and thereby providing the added signal S ADD1 to be recorded. Referring now to Figure 7, it will be seen that a video disc player according to an embodiment of this invention is shown to include a signal processing circuit 40 which allows the video disc player to reproduce either a conventional video disc recorded with a standard composite video signal, or a high-resolution video disc recorded, as previously described with reference to Figure 5, with a component video signal having a wide band luminance signal. More specifically, in a video disc player having the signal processing circuit 40 illustrated in Figure 7, a video disc is rotated by a suitable spindle motor (not shown), and the video signal recorded on the rotated video disc is reproduced, for example, by an optical pick-up or head (not shown) so as to provide a reproduced video signal which is supplied to a demodulating circuit 4. If a conventional video disc, that is one recorded with a composite video signal, is being reproduced, the demodulating circuit 4 derives the composite video signal from the reproduced signal. On the other hand, when a high-resolution video disc is being reproduced, the demodulating circuit 4 derives therefrom the added signal S ADD1 composed of the mixed luminance signal S GO and the chroma signal S CK . A high-pass filter circuit (HPF) 41 has a cut-off frequency substantially corresponding to the lower end of the chroma band so as to extract from the output of the demodulating circuit 4 a signal component having a frequency band that includes the chroma band and extends substantially higher than the latter, for example, up to the limit of 7 MHz that can be recorded and reproduced on the video disc. This extracted signal component is supplied from the HPF 41 to a comb-type filter circuit 6 which, when a conventional video disc is being reproduced, derives a chroma signal from the output of the HPF 41. On the other hand, when a high-resolution video disc is being reproduced, the comb-type filter circuit 6 derives from the output of the HPF 41 both the chroma signal S CK and the frequency-converted slant direction luminance signal S LY having a frequency higher than the chroma band, but which contains slant spectrum luminance information from the chroma band. The output of the comb-type filter circuit 6 is supplied to a subtracting circuit 7 so as to be subtracted by the latter from the output of the demodulating circuit 4. If a conventional video disc is being reproduced, the chroma signal extracted by the filter circuit 6 is subtracted from the reproduced composite video signal so as to provide a luminance signal at the output of the subtracting circuit 7. However, if a high-resolution video disc is being reproduced, the chroma signal S CK and the frequency-converted intermediate luminance signal S LY derived by the filter circuit 6 are subtracted from the reproduced added signal S ADD1 so as to provide, at the output of the subtracting circuit 7, the suppressed luminance signal S YK (Figure 6E) from which the intermediate luminance signal is dropped-out in the frequency band that includes the chroma band and extends thereabove to the upper limit (7 MHz) of the luminance signal band. The output of the comb-type filter circuit 6 is also supplied to a low-pass filter circuit (LPF) 43 which has a cut-off frequency substantially corresponding to the upper end of the chroma band so as to extract the chroma signal S CK from the output of the comb-type filter circuit 6. Thus, when a composite video signal recorded on a conventional video disc is reproduced, the luminance signal and the chroma signal can be separately obtained from the outputs of the subtracting circuit 7 and the LPF 43, respectively. When a high-resolution video disc is reproduced, the chroma signal S CK is obtained as the output of the LPF 43 separate from the frequency-converted intermediate luminance signal S LY which is in this case included therewith at the output of the comb-type filter circuit 6. A further high-pass filter circuit (HPF) 45 is also connected to the output of the comb-type filter circuit 6 and has a cut-off frequency substantially corresponding to the upper end of the chroma band. Accordingly, when a conventional video disc is being reproduced so that the output of the filter circuit 6 consists only of the chroma signal, no signal passes through the HPF 45. On the other hand, when a high-resolution video disc is being reproduced, the HPF 45 extracts the frequency-converted intermediate luminance signal S LY from the output of the comb-type filter circuit 6. The frequency-converted intermediate luminance signal S LY appearing at the output of the HPF 45 is multiplied by a reference signal S OSC in a multiplier circuit 47 and the output of the latter is fed to a further low-pass filter circuit (LPF) 49 having a cut-off frequency substantially corresponding to the upper end of the chroma band. Thus, when a high-resolution video disc is being reproduced, the multiplier circuit 47 and the LPF 49 operate to reconvert the frequency-converted intermediate luminance signal S LY back to the original frequency band, that is, the chroma band, while interleaving the reconverted low frequency portion of the intermediate luminance signal, S SI , with the suppressed luminance signal S YK being then obtained from the output of the subtracting circuit 7. Thus, the output of the LPF 49 is the reconverted low frequency portion of the intermediate luminance signal, S SI (Figure 6F), that is, the reproduced slant spectrum luminance information of the chroma band. The reproduced low frequency portion of the intermediate luminance signal, S SI , obtained from the LPF 49 is added to the suppressed luminance signal S YK by an adding circuit 51 to provide, at the output of the latter, a reproduced luminance signal S SHO in which slant direction luminance information is dropped-out or missing only in the frequency band higher than the chroma band. Accordingly, when a video disc player having the signal processing circuit 40 according to the present embodiment is used for playback or reproduction of a conventional video disc, the luminance signal and the chroma signal are readily separated from the reproduced composite video signal. On the other hand, when a high resolution video disc recorded in the manner previously described with reference to Figure 5 is being reproduced, the signal processing circuit 40 makes it possible to obtain the chroma signal S CK and the wide band luminance signal S SHO having its resolution in the lateral direction extended to 7 MHz and its resolution in the slant spectral portion extended to the upper end of the chroma band. It will be appreciated that, in the embodiment of the invention described with reference to Figure 7, the comb-type filter circuit 6, the subtracting circuit 7, the HPFs 41 and 45 and the LPF 43 constitute separating means by which the reproduced added signal S ADD1 is separated into the chroma signal S CK , the frequency-converted intermediate luminance signal S LY and the suppressed luminance signal S YK . Further, in the signal processing circuit 40, the multiplying circuit 47 and the LPF 49 constitute frequency-converting means for reconverting the separated frequency-converted intermediate luminance signal S LY back to the chroma band and in frequency-interleaved relation with the suppressed luminance signal S YK . Finally, in the signal processing circuit 40, the adding circuit 51 adds the reconverted low frequency portion of the intermediate luminance signal, S SI , to the suppressed luminance signal S YK for providing the wide band luminance signal S SHO , while the chroma signal S CK is separately provided from the LPF 43. Since the slant spectrum luminance information in the chroma band is frequency-converted to a higher frequency band, that is to the signal S LY , for recording, and upon reproduction, is frequency reconverted to the original frequency band, that is back to the chroma band, the reproduced luminance signal S SHO contains all of the lateral and slant spectrum luminance information at least to the upper end of the chroma band, so that it is possible to reproduce a display picture of high image quality while providing a video disc player that is compatible with conventional video discs recorded with composite video signals. In the specifically described embodiment of this invention, the bandwidth of the slant direction luminance signal S SI , and hence of the frequency-converted intermediate luminance signal S LY , is limited by the LPF 23 (Figure 5). In other words, only that portion of the intermediate luminance signal S HY (Figure 6D) in the chroma band constitutes the low-frequency portion of the luminance signal, S SI , which is then frequency-converted to form the frequency-converted intermediate luminance signal S LY . However, the present invention is not limited to this arrangement. By way of example, the cut-off frequency of the LPF 23 may be selected to be higher than the upper end of the chroma band, or the LPF 23 may be omitted. In such a case, the frequency-converted intermediate luminance signal S LY may extend further in the direction of the higher frequencies so that upon reproduction, as previously described, the resolution in the slant direction can be improved and a picture of even higher image quality can be obtained. Although the low-frequency portion of the intermediate luminance signal, S SI , has been described as being frequency-converted by multiplying the same with the reference signal S OSC having the frequency 534 f H , the frequency of the reference signal S OSC is not limited to that value, and can be freely changed as long as the frequency-converted slant direction luminance signal S LY is provided with a comb-tooth characteristic similar to that of the chroma signal S CK and is frequency-interleaved with the suppressed luminance signal S YK . Further, although compatibility with the NTSC standard composite video signal has been established in the above-described embodiments of the invention, it will be appreciated that the invention can be similarly applied to other systems, for example, to cases where compatibility with PAL or SECAM standard video signals is to be established. Moreover, although in the above-described embodiments of the invention, the component video signal has been described as being recorded on and reproduced from a video disc, it will also be appreciated that the invention may be readily applied to recording on other recording media, such as magnetic tape or the like, and also to video signal processing apparatus for transmitting and receiving a component video signal or the like. Thus, a video signal processing apparatus embodying this invention may be provided with dual functions, that is recording and reproducing or transmitting and receiving.

Claims: A signal processing circuit for an apparatus for recording or transmitting a component video signal having a wide frequency band luminance signal (S YH ) so as to be reproducible or receivable to obtain a picture of high resolution and a chroma signal (S CL ) in a chroma band included within said frequency band of the luminance signal (S YH ) and being substantially below the high end thereof, the signal processing circuit (20) comprising: means (10,12,21) receiving said luminance signal (S YH ) for separating therefrom an intermediate luminance signal (S HY ) with a frequency band spectrum extending from the lower band limit of said chroma band to the upper end of the luminance spectrum and having notches at uniform frequency intervals, and for suppressing said luminance signal (S YH ) by said intermediate luminance signal (S HY ) so as to obtain a suppressed luminance signal (S YK ) such that, in its spectrum, for a frequency band extending from the lower band limit of said chroma band to the upper end of the luminance spectrum, notches are formed at said uniform frequency intervals; frequency-converting means (23,25,26) for frequency-converting a spectral portion (S SI ) of said intermediate luminance signal (S HY ) in said chroma band to a frequency-converted intermediate luminance signal (S LY ) which is frequency interleavable with said suppressed luminance signal (S YK ) and which is in a frequency band higher than said chroma band; means (9) for generating from said chroma signal (S CL ) a modified chroma signal (S CK ) at the same spectral position as said first-mentioned chroma signal (S CL ) and which is modified to be frequency-interleavable at the notches of the notched frequency band of said suppressed luminance signal (S YK ); and means (13,29) for adding said suppressed luminance signal (S YK ), said frequency-converted intermediate luminance signal (S LY ) and said modified chroma signal (S CK ) so as to provide an added signal (S ADD1 ) to be recorded or transmitted. A circuit according to claim 1, wherein said means for separating said intermediate luminance signal (S HY ) includes high-pass filter means (21) for passing the frequency band of said luminance signal that includes and extends above said chroma band, and comb-type filter means (10) acting on the output of said high-pass filter means (21). A circuit according to claim 2, wherein said means for suppressing said luminance signal (S YH ) includes subtracting means (12) for subtracting an output (S HY ) of said comb-type filter means (10) from said luminance signal (S YH ) of the component video signal. A circuit according to claim 2 or claim 3, wherein said means for generating the modified chroma signal (S CL ) comprises second comb-type filter means (9) having a frequency characteristic substantially the same as a frequency characteristic of the first-mentioned comb-type filter means (10). A circuit according to claim 4, wherein each of said first and second comb-type filter means (9,10) is operable to suppress the level of the respective signals at frequencies that are spaced apart by a horizontal frequency (f H ) of the component video signal. A circuit according to any one of the preceding claims, wherein said frequency-converting means includes low-pass filter means (23) having a cut-off frequency corresponding substantially to the upper end of said chroma band so as to provide, as an output (S SI ) from said low-pass filter means (23), a frequency band of said intermediate luminance signal corresponding to said chroma band, and means (25) multiplying said output (S SI ) from the low-pass filter means (23) by a predetermined frequency (S OSC ) for obtaining said frequency-converted intermediate luminance signal (S LY ) which is frequency interleavable with said suppressed luminance signal (S YK ). A circuit for processing a recorded or transmitted video signal for an apparatus for reproducing or receiving the recorded or transmitted video signal, the video signal being of the form of the added signal (S ADD1 ) as generated by the circuit defined in claim 1 and thereby composed of a suppressed luminance signal (S YK ) frequency interleaved with a modified chroma signal (S CK ) and also with a frequency-converted intermediate luminance signal (S LY ) in a frequency band higher than the chroma band, the processing circuit (40) comprising: separating means (6,7,41,43,45) receiving the reproduced or received video signal (S ADD1 ) for separating therefrom said modified chroma signal (S CK ), said frequency-converted intermediate luminance signal (S LY ) and said suppressed luminance signal (S YK ); frequency-converting means (47,49) for reconverting the separated frequency-converted intermediate luminance signal (S LY ) to said chroma band and in frequency interleaved relation to said suppressed luminance signal (S YK ); and adding means (51) for adding the reconverted intermediate luminance signal (S SI ) and the separated suppressed luminance signal (S YK ) so as to provide therefrom a luminance signal (S SHO ) in which oblique spectrum luminance information is dropped-out in notches only in a frequency band above said chroma band and which forms, with the separated chroma signal (S CK ), a component video signal. A circuit according to claim 7, wherein said separating means includes high-pass filter means (41) having a cut-off frequency substantially corresponding to the lower end of said chroma band, comb-type filter means (6) receiving an output of said high-pass filter means (41) for deriving therefrom said chroma signal (S CK ) and said frequency-converted intermediate luminance signal (S LY ), low-pass filter means (43) receiving an output of said comb-type filter means (6) and having a cut-off frequency substantially corresponding to the upper end of said chroma band for passing said modified chroma signal (S CK ), and subtracting means (7) for subtracting said output of the comb-type filter means (6) from said reproduced or received video signal (S ADD1 ) so as to provide said separated suppressed luminance signal (S YK ). A circuit according to claim 8, wherein said frequency-converting means includes second high-pass filter means (45) having a cut-off frequency substantially corresponding to the lower end of the frequency band of said separated frequency-converted intermediate luminance signal (S LY ), and means (47) multiplying an output from said second high-pass filter means (45) by a predetermined frequency (S OSC ) for obtaining the separated frequency-converted intermediate luminance signal (S SI ) reconverted to said chroma band. Apparatus for recording and/or reproducing or for transmitting and/or receiving a component video signal, the apparatus including a signal processing circuit (20) according to any one of claims 1 to 6 and a processing circuit (40) according to claim 7, claim 8 or claim 9.

Inventors: GANSE SHIGERU, GANSE, SHIGERU, GANSE, SHIGERU, C/O PATENTS DIVISION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: H04N9
IPC codes: H04N11, H04N9