JPS6051386A - Color difference signal processing device - Google Patents

Abstract

PURPOSE:To reduce remarkably an edge error of a picture, and to improve a picture quality by forming plural digital color difference signals from a solid- state image pickup element in one set, executing its adding operation, and averaging them. CONSTITUTION:The color difference signal is fetched successively from inside of a picture element in a solid-state image pickup element arranged in such a scanning direction as a different chrominance signal is repeated alternately at every picture element (Ai, Bi (i=1,2...) show each picture element signal level). With respect to all digital color difference signals, a set of plural, for instance, two digital color difference signal units is made, an operation for adding its set and dividing it by two is executed and a new digital color difference signal is obtained. it is obtained by considering all the digital color difference signals, therefore, an edge error can be reduced. Also, the color difference signal is outputted by a position 402 of a boundary edge of a white and black object to be photographed having no color difference component, but this gain is suppressed to a half comparing with a conventional one.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color difference signal processing device that can be used for digital signal processing in color video cameras and the like.

Structure of a conventional example and its problems FIG. 1 shows an overall block diagram of a color video camera simply digitized.

The analog signal read from the solid-state image sensor 101 is
After converting it into a digital signal through the D converter 102, it is separated into a luminance signal and a color signal, and the luminance signal digital processing circuit 1o3゜color signal digital processing circuit 1 is used.
04 performs digital signal processing, and the chrominance signal passes through the synchronization circuit 105 and is mixed with the luminance signal in the encoder 106.
Finally, the D/A converter 107 outputs the signal as an NTSC standard signal.

The color signal digital processing circuit 104 creates a level difference between each pixel of digital pixel signals sequentially extracted in the scanning direction, and handles this as a color difference signal.

The synchronization circuit is composed of a high-speed RAM with a storage capacity capable of storing as data the digital color difference signal obtained from one line of pixel arrays in the solid-state image sensor. By writing and reading each digital color difference signal, it is synchronized with the digital color difference signal of the previous line.

If we simply consider color signal digital processing, it is shown in Figure 2 (
-), it can be returned in the form shown in (b).

FIG. 2(a) shows a method for sequentially extracting color difference signals from a pixel column 201 in a solid-state image sensor arranged in the scanning direction so that different color signals are alternately repeated for each pixel. At and Bi (i=1.2°...) in the figure represent each pixel signal level. That is, groups are created in units of two pixels in the scanning direction, the difference is taken between each group, and the color difference signal A1-El is obtained.
, A2-B2. A3-B5. ...... is obtained.

In this method, color difference signals A2-B1 . A3-B2. ... is not obtained, so the color difference information is halved. Unfortunately, for subjects with particularly strong contrast, even if the subject is a black and white image, the color difference signal may be detected as a false signal at the boundary, or may not be detected, resulting in a colored pattern. Significantly degrades image quality.

As shown in FIG. 2(b), the color difference signal A2-B is created by another two-pixel unit set that was not shown in the figure (-).
1. A3-B2. By adding ......, all color difference information can be extracted. However, if these color difference information are directly processed, twice as many color difference signals as in the case (-) in the same figure will be handled, so the clock frequency for data flow will also be doubled. As a result, not only does the time margin of the 5-bed signal become smaller, but the memory capacity required for signal processing in the synchronization circuit also becomes twice as large, increasing the circuit scale and, therefore, increasing power consumption. There are problems.

OBJECTS OF THE INVENTION The present invention obviates these conventional drawbacks,
The present invention provides a color difference signal processing device that has sufficient information for color reproduction and can set a low clock frequency for signal data flow.

Structure of the Invention The color difference signal processing device of the present invention generates a digital color difference signal from a solid-state image sensor, divides the sequentially obtained digital color difference signals into a plurality of units in the order in which they are obtained, and processes the digital color difference signals for each set. The signal is added and averaged, and the time tolerance of the signal data flow clock is increased to reduce power consumption.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

6'''-]' Figure 3 shows the principle of the color difference signal processing device of the present invention. That is, for all the digital color difference signals obtained in Figure 2(b), a plurality of, for example two digital A new digital color difference signal is obtained by creating a set of color difference signal units, adding the sets and dividing by 2. In this case, since there are 2 digital color difference signals in each set, 2
Dividing by corresponds to the averaging operation.

The digital color difference signal level /I10° obtained by this operation is generally expressed as follows.
=1.2. ...) Since this digital color difference signal is obtained by taking all digital color difference signals into consideration, edge errors in particular can be significantly reduced.

FIG. 4(a), Φ) shows how the color difference signal changes depending on the position 401 and 402 of the boundary edge of a monochrome object that does not have a color difference component. When the boundary edge is 4011g, Fig. 2 (
FIG. 4 (-) shows the change in color difference signals in case a) and in the case of FIG. 3 of the present invention. Similarly, the boundary edge is shifted by one pixel and is at the position 402, as shown in FIG.

As can be seen from the above, if the method in the case of Fig. 2 (a) is used, no color difference signal that becomes a false signal is generated in Fig. 4 (-), but a false signal appears greatly. On the other hand, in the case of FIG. 3 in which the present invention is applied, FIG.
In both cases a) and (b), color difference signals serving as false signals are generated at the same level, but the gain is suppressed to half that of the case in FIG. 2(a).

This is because the color difference signals are averaged and added.

As a result of the above, in the case of FIG. 2(a), as the boundary edge moves, the false signal at the edge portion changes significantly, and the image quality deteriorates significantly. Even if the boundary edge does not move, if the boundary edge becomes sharp, a colored striped pattern will appear on the edge.

However, in the case of FIG. 3 using the present invention, although the false signals are not completely eliminated, they are all reduced to half. Moreover, even if the boundary edge moves or is diagonal,
The false signal does not change and the image is not degraded.

As described above, according to the present invention, an image with few edge errors can be obtained with a low sampling clock frequency.

FIG. 5 is a circuit diagram for concretely realizing the present invention. A timing chart of the flow of digital pixel signal data 601 and the clock pulses applied to each latch circuit is shown in FIG.

The digital pixel signal data 501 is the Sochi circuit 502.
．． 503, A1. A2. The flow of... and B1. B2. It is divided into the flow of...

Then, these data pass through the subtraction circuit 504, and are further processed by latch circuits 505, 506 into A1-B1. A
2-B2.・・・・Flow and A2-B1. A3-
B2. It is divided into the flow of... These two data streams are both shifted one bit lower and pass through adder circuit 507. That is, the color difference signals are averaged and added here. Lower 1 pit shift of data 9.

corresponds to halving the signal gain.

Finally, the color difference signal 51 passes through the latch circuit 508.
4 is obtained.

Note that the frequency of the clock pulse used is half of the sampling clock frequency f6 of the pixel signal,
There is a large amount of time available.

The present invention can also be applied to a solid-state image pickup device with simultaneous two-line readout in a staggered arrangement, as shown in FIG. The same correspondence as in FIG. 3 can be given to the two lines 701 and 702 for simultaneous reading. In addition, 2 simultaneous reading
The two lines 7o1 and 702 do not switch regardless of whether they are even lines or odd lines. FIG. 8 is a circuit diagram for concretely realizing FIG. 7. The only difference from FIG. 5 is that the digital pixel signal is originally divided into two parts and output, and each of the constituent circuit elements 502 to 508 is the same, and the clock and clock signals of each latch circuit are exactly the same. (The timing relationship for Luz is 0, which is exactly the same as in Figure 6, and the pixel arrangement is staggered, so
The black and yaw frequencies are twice as high as those in FIG.

In addition, as an example of the operation of adding and averaging the color difference signals of the present invention, the obtained color difference signals were sequentially divided into two parts and treated as one set.
It is not necessary to consist of two color difference signals.

As the number of pixels for one line in the solid-state image sensor increases, the number of color difference signals obtained also increases.
By creating a set of two or more color difference signals and performing an averaging operation on the set, necessary and sufficient new color difference information can be obtained as in the above embodiment. Generally, when a set of n color difference signals is averaged, the edge error signal level is reduced to 1/n. Therefore, if the number of pixels in the solid-state image sensor increases in order to obtain the necessary and sufficient color difference information, the number of color difference signals in one set can be increased accordingly and the averaging operation can be performed, thereby reducing edge errors. It can be further reduced. Of course, the frequency of the clock pulse for the color difference signal data flow created by the averaging operation is 1/fl of the frequency of the clock pulse for extracting the pixel signal, so the time margin is also very tight. Low power consumption can be achieved.

Effects of the Invention As described in Section 2, the color difference signal processing device of the present invention performs an addition operation on a plurality of digital color difference signals from a solid-state image sensor and averages them into a set. As a result, edge errors on the screen can be significantly reduced 17 and image quality can be improved.

Further, the clock frequency used in the device is only half the pixel signal sampling clock frequency if two sets of color difference signals are processed, so the time margin is large and the power consumption is small.

Moreover, the memory capacity required for signal processing in the synchronization circuit is also half of that required when handling the original color difference signals as they are.

Therefore, the overall circuit scale is reduced, the number of parts can be reduced, and costs can be reduced, which has great practical effects.

[Brief Description of the Drawings] Figure 1 is a digitalized overall diagram of a conventional color video camera, Figure 2 (a) is a principle diagram of a conventional color difference signal processing device, and Figure 3 is a diagram of the principle of a conventional color difference signal processing device. is a principle diagram of the color difference signal processing device of the present invention, FIGS. 4(a) and 4(b) are diagrams showing changes in color difference signals with respect to edge signals in a conventional example and an embodiment of the present invention, and FIG. is a circuit diagram showing an embodiment of the present invention, FIG. 6 is a timing chart of FIG. 5, FIG. 7 is a principle diagram of another color difference signal processing device of the present invention, and FIG.
FIG. 3 is a circuit diagram showing another embodiment of the present invention. 502, 503, E505, 506, 508, =
----- La. . Child circuit, 604...Subtraction circuit, 507...
...Addition circuit.

Claims (3)

[Claims] (1) Generating digital color difference signals from solid-state image sensors,
The method is characterized in that the digital color difference signals that are sequentially processed are divided into a plurality of obtained nine applications, each of which is made into one set, and the plurality of digital color difference signals in the set are added and averaged for each set. Color difference signal processing device. (2) Pixel signals are sequentially extracted in the scanning direction from a solid-state image sensor that outputs pixel signals consisting of pixel signals consisting of repetitions of different color signals alternately in the scanning direction, and after digital conversion, each digital pixel is 2. The color difference signal processing device according to claim 1, wherein a digital color difference signal is created by taking the difference between the signal and digital pixel signals before and after the signal in the scanning direction. (3) The pixel arrangement in the scanning direction of odd-numbered lines and the pixel arrangement in the scanning direction of even-numbered lines are shifted by half a pixel, and pixel signals from odd-numbered lines and pixel signals from even-numbered lines can be read out simultaneously. After sequentially extracting pixel signals in the scanning direction from a staggered array simultaneous 2-line readout solid-state image sensor and converting them into digital data, the color difference is sequentially calculated from the digital pixel signals extracted from the odd-numbered lines and the digital pixel signals extracted from the even-numbered lines. 2. The color difference signal processing device according to claim 1, wherein the color difference signal processing device generates a signal.