Y/C separator

Abstract: An object of the invention is to avoid situations in which a vertical resolution is decreased and a deviation of the displayed image when a progressive scanning image information is generated based on a interlace scanning image information. In a color signal generating circuit 5, color signals (R, G, B) are generated based on a image signal of an odd field of an interlace scanning. A luminance signal generating arrangement (1) generates an interpolation luminance signal based on the color signals (R, G, B) from the color signal generating circuit 5.

Description: The present invention relates to a Y/C separator which generates luminance signal components and a chrominance (color difference) signal component of a sequential scanning system on the basis of an image signal of an interlaced scanning system and to a camera comprising such a Y/C separator. In case of generating a luminance signal and a color difference signal on the basis of an image signal outputted from an image pick-up device such as a CCD or the like, a Y/C separation circuit (Y: Luminance signal, and C: Color difference signal) is used. The Y/C separation circuits include a circuit which simply generates a luminance signal and a color difference signal, and additionally to this, for example, a circuit provided with a function which receives an image signal of an interlaced scanning system and generates a luminance signal and a color difference signal of a sequential scanning system. Up to now, conversion from an interlaced scanning system to a sequential scanning system has been realized, for example, by repeating twice to scan each of scanning lines forming an odd field. There is a possibility that a moving image is displayed in a slipped-off state when displaying simply repeatedly one scanning line. And to display repeatedly the same scanning line means that scanning lines having the same content are disposed in parallel with one another, and this causes a problem that the resolution in the vertical direction is deteriorated. It is an object of the present invention provide a Y/C separator capable of avoiding slippage of an image and deterioration of the resolution in the vertical direction. To this end, a primary aspect of the invention provides a Y/C separator as defined in claims 1, 4 and 5. Advantageous embodiments are defined in the dependent claims. According to such a composition, the present invention can make all scanning lines almost different in content from one another without repeating one scanning line. Thanks to this, it can avoid slippage of an image and deterioration of the resolution in the vertical direction which have been generated in case of using repeatedly one scanning line. The invention will now be explained with reference to the drawings. Fig. 1 is a diagram of Y/C separator in accordance with the invention. Fig. 2 is a first diagram to explain the operation of the invention. Fig. 3 is a second diagram to explain the operation of the invention. Figure 1 shows a block diagram of a Y/C separation circuit of the present invention. As shown in the figure, a Y/C separation circuit of the invention has an analog-to-digital converter (AID) 3 linked to a CCD 2 for interlaced scanning, a luminance signal generating circuit (LSG) 4, a color signal generating circuit (buffer; BUF) 5, an arithmetic circuit (CPU) 6, and a color signal generating circuit (CSG) 7. The A/D converter 3 is a known circuit composed of a logic device for converting the form of an image signal from an analog form to a digital form, and the like. The luminance signal generating circuit 4 is composed of a logic circuit for generating a luminance signal Y on the basis of an image signal. The buffer 5 is a circuit having a logic circuit for realizing an arithmetic function which generates color signals R, G and B of red, green and blue on the basis of an image signal, and a memory device for realizing a storage function which stores the color signals. The arithmetic circuit 6 is a microprocessor which controls the timing for the luminance signal generating circuit 4 to generate a luminance signal Yodd and generates an interpolation luminance signal Yeven on the basis of color signals R, G and B stored in the buffer 5. The color signal generating circuit (CSG) 7 is a known circuit composed of a logic device for generating a color difference signal on the basis of color signals R, G and B, and the like. Here, since both of the luminance signal generating circuit 4 and the arithmetic circuit 6 are circuits related to generation of a luminance signal, both of them are collectively referred to as a luminance signal generating means 1. Operation of a Y/C separation circuit according to the invention having the above-mentioned composition is described with reference to Figures 2 and 3. Figure 2 is a first operation explaining figure according to the invention. Figure 2(a) shows arrangement of color filters of the CCD 2. In case that a scanning operation for making an odd field is started, from this CCD 2, columns C1, C2, C3 and so forth of rows R1 and R2 which form a line n are first read out, and then columns C1, C2, C3 and so forth of rows R3 and R4 which form a line n+1 are read out. After this, until all of the image signals forming the odd field are obtained, reading out lines two by two, namely, reading out lines n+2, n+3, and so forth is continued. The luminance signal generating circuit 4 generates a luminance signal Yodd on the basis of the read-out image signal. On the other hand, the buffer 5 generates color signals R, G and B, and at the same time, stores these color signals. The color difference signal generating means 7 generates a color difference signal C, using these color signals R, G and B. Here, a case of generating a luminance signal Y and a color difference signal C of an odd field is described in more detail. As shown in Figure 2(b), a luminance signal Y of the line n is represented by Y11, Y12, Y13 or the like. These luminance signals are computed by operations in the luminance signal generating circuit 4, namely, operations (Ye + Mg) and (Cy +G). On the other hand, color signals R, G and B of the line n are represented by (R11, G11 and B11), (R12, G12 and B12), and so forth. As appears from Figure 2(b), image data of two pixels are formed by combination of color signals R11, G11 and B11 and luminance signals Y11 and Y12. In the same way, image data of two pixels are formed by combination of color signals R12, G12 and B12 and luminance signals Y13 and Y14, or combination of color signals R31, G31 and B31 and luminance signals Y31 and Y32. That is to say, image data of two pixels are formed by combination of a set of color signals and two luminance signals. The timing when the luminance signal generating circuit 4 outputs a luminance signal Yodd is realized by control of the arithmetic circuit 6. The arithmetic means 6 controls the output timing of a luminance signal synchronously with the read-out timing of the CCD 2. In case of an ordinary interlaced scanning, a scanning for making an odd field is performed and then a scanning for making an even field is performed, namely, reading out for forming lines n', n' + 1, and so forth is performed. However, a Y/C separator of the invention generates an interpolation field instead of reading out lines n', n' + 1, and so forth. A process of forming an interpolation field is realized by referring to color signals generated by the buffer 5 on the basis of image signals of a previously stored odd field. That is to say, the arithmetic circuit 4 generates a luminance signal Yeven on the basis of color signals R, G, B, generated by the buffer 5. On the other hand, the color difference signal generating means 7 generates a color difference signal C on the basis of color signals R, G and B. In order to generate a luminance signal Yeven of an interpolation field, the invention uses color signals R, G and B (R11, G11, B11, R12, G12, B12, R31, G31, B31, and so forth) shown in Figure 2(b). That is to say, the arithmetic circuit 6 generates color signals Cy, Mg, Ye and G on the basis of color signals R, G and B of an odd field stored in the buffer 5. Concretely, as shown in Figure 3(a), it generates color signals Mg11c and G12c on the basis of color signals R11, G11 and B11. In the same way, it generates color signals Ye21c and Cy22c on the basis of color signals R31, G31 and B31. After this, in the same way, it generates color signals Mg13c and G14c on the basis of color signals R12, G12 and B12, and generates color signals Ye23c and cyan Cy24c on the basis of color signals R32, G32 and B32. Next, as shown in Figure 3(b), the arithmetic circuit 6 generates luminance signals Y21, Y22, etc., and Y41, Y42, etc., on the basis of color signals Cy, Mg, Ye and G generated in the above-mentioned manner. That is to say, it generates a luminance signal Y21 on the basis of color signals Mg11c and Ye 21c, a luminance signal Y22 on the basis of color signals G12c and Cy22c, and a luminance signal Y23 on the basis of color signals Mg13c and Ye23c. In a manner as described above with reference to Figure 2(b), these luminance signals are referred as a luminance signal Yeven at the time of generating image data (used for an interpolation field). That is to say, image data of two pixels are formed by combination of color signals R11, G11 and B11, and luminance signals Y21 and Y22. In the same way, image data of two pixels are formed by combination of color signals R12, G12 and B12, and luminance signals Y23 and Y24, or combination of color signals R31, G31 and B31, and luminance signals Y41 and Y42. That is to say, image data of two pixels are formed by combination of a set of color signals and two luminance signals. As described above, the invention can make an interpolation field having luminance signals different from luminance signals forming an odd field. Being different in luminance signals means that scanning lines adjacent to each other are different in content from each other. In case of realizing an image display directly on the basis of color signals without generating color difference signals, it can do to realize an image display by directly referring to color signals read out from the buffer 5 without doing so through the color difference signal generating means 7. According to a Y/C separator of the invention, since luminance signals which form an odd field and luminance signals which form an interpolation field are different from each other, substantially different scanning lines are arranged. Therefore, it is possible to improve almost double the resolution in the vertical direction in comparison with a case of repeating twice the same scanning line. Fidelity to an image caught by a CCD is improved and it can be avoided for a moving image to be slipped off on a display screen.

Claims: A Y/C separator for generating luminance signal components and a color difference component signal of a sequentially scanned image signal from an interlaced scanned image signal, comprising: means (5) for generating color signals based on an input image signal of interlaced scanning, and for storing the color signals for a field period of the input image signal; means (1) for generating luminance signal components based on the input image signal; and means (7) for generating a color difference signal based on the color signals stored in said color signals generating and storing means; wherein the luminance signal generating means (1) further comprises: means (4) for generating a first luminance signal component (Yodd) ; and means (6) for generating an interpolation luminance signal component (Yeven) as a second luminance signal to be interposed between lines of said first luminance signal, based on the color signals stored in the color signals generating and storing means. The Y/C separator as claimed in claim 1, in which the luminance signal generating means (1) includes a luminance signal generating circuit (4) for generating the first luminance signal, and the interpolation luminance signal generating means (6) includes a calculating circuit for generating the interpolation luminance signal. The Y/C separator as claimed in claim 1, wherein the input image signal includes color signals of Cyan, Magenta, Yellow and Green. A color camera for supplying luminance signal components and a color difference signal component of a sequentially scanned image signal, said color camera comprising: a CCD sensor for furnishing an initial image signal of interlaced scanning; means (5) for generating color signals based on the initial image signal, and for storing the color signals for a field period of the initial image signal; means (1) for generating luminance signal components based on the initial image signal; and means (7) for generating a color difference signal based on the color signals stored in said color signals generating and storing means; wherein the luminance signal generating means (1) further comprises: means (4) for generating a first luminance signal component (Yodd) ; and means (6) for generating an interpolation luminance signal component (Yeven) for use as a second luminance signal to be interposed between lines of said first luminance signal, based on the color signals stored in the color signals generating and storing means. A method of producing luminance signal components and a color difference signal component of a sequentially scanned image signal, comprising the steps: generating an image signal of interlaced scanning; generating color signals based on the image signal; storing the color signals for a field period of the image signal; generating a first luminance signal component based on the image signal; generating an interpolation luminance signal component as a second luminance signal to be interposed between lines of said first luminance signal, based on the stored color signals; and generating a color difference signal component for the sequentially scanned color image signals based on the stored color signals.

Inventors: SUTO NOBUJI C O INT OCTROOIBUR, SUTO, NOBUJI, Suto, Nobuji,c/o Int. Octrooibureau B.V.
Applicants: KONINKL PHILIPS ELECTRONICS NV, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1997
Main classification: H04N9
IPC codes: H04N9