JPS6330078A - Picture signal converter - Google Patents

Abstract

PURPOSE:To prevent a duplicated image or a fogged picture in following to a moving object image by confirming from which field movement takes place depending on each movement signal so as to select properly either in-field interpolation or inter-field interpolation. CONSTITUTION:Moving signals a-d between consecutive fields are outputs of a delay circuit 26, a comparator circuit 22, a delay circuit 28 and a delay circuit 24 respectively. Three stages of field memories 12, 14 and 16 are provided to an input picture signal x1, the field subjected to interpolation is shifted before by one field and the interpolation of a field (i-1) is discriminated (either in-field interpolation or inter-field interpolation) by using the moving signals a-d. For example, as shown in figure, an interpolation selection signal S (output of an OR circuit 34) is expressed as S=a.b+c .d, the presence of the movement at a point A of a noticed field (i-1) is confirmed in the 1st term a.b and the presence of the movement of a point D being an inter-field interpolation signal is confirmed by the 2nd term c.d. Thus, if movement exists in the point D, the in-field interpolation is selected for the field (i-1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for converting an image signal such as a television signal from inclace scanning to non-interlaced scanning.

[Conventional technology]

As a method for obtaining a high-definition image from a current interlaced video signal such as NTSC, a non-interlaced method has been proposed in which the scanning lines of one field are doubled, for example.

To double the number of scanning lines, the problem is how to generate an interpolation signal between scanning lines. For example, intrafield interpolation uses the average value of two adjacent lines in the same field as the interpolation signal, and Interfield interpolation uses the corresponding signal of the field as an interpolation signal as it is,
A method of switching according to the movement of the image has been proposed.

In this method, the accuracy of motion detection in the object image is an important factor that affects the image quality, but in general, the presence or absence of motion is determined based on whether there is a significant difference in the difference signal (frame difference) between the front and rear fields. There is. However, in the current field, there may be cases where no significant difference appears in the difference signals between the front and rear fields even in a moving area, and in such cases, this type of determination method may cause significant image quality deterioration such as double images. There is.

This image quality deterioration will be explained with reference to FIGS. 2 and 3.

11>-(6) in FIG. 2 correspond to (1)-(6) in FIG. In FIGS. 2 and 3, the shaded area indicates selection of intra-field interpolation. Now, in field i −1 (2
The object image shown by the thick line, which was stationary at the position of ), moves from ■ to ■ in field i, and in field i+l it moves to (
Suppose that it comes to rest at position 4). At this time, if motion detection is performed using the difference signal between the front and rear fields, in the area indicated by ■ and ■ in field i in FIG.
, Intra-field interpolation is selected because there is a significant difference in the frame differences of ■, but since there is no significant difference in the frame differences of In the region marked ■ in FIG. 2, a signal corresponding to the background image of the previous field is interpolated, causing double image interference.

As a countermeasure against this problem, a method has been proposed in which, as shown in FIG. 4, a motion is determined when a significant difference occurs in any of the frame difference signals of adjacent fields. That is, if there is a significant difference in either ■ or ■° in FIG. 5, it is determined that there is movement. In the illustrated example, there is a significant difference in the frame difference of "■", so the area marked "■" in FIG. 4 is determined to be motion,
Intra-field interpolation is selected to remove double image disturbances.

Note that in FIGS. 4 and 5, the shaded areas indicate selection of intra-field interpolation.

However, in this method, as shown in FIG. 4, intra-field interpolation signals are selected over a wide range even though fields i-1 and i+2 are stationary. Visually, this appears on the screen as a low-resolution image (so-called blurred image) that follows the moving object image before and after, causing unnaturalness in the moving image. In particular, the higher the resolution of the background image, the more significant the deterioration.

As a method to improve this, the inventor of the present invention has disclosed in another patent application that the motion determination result is delayed and a motion field is determined from the delayed motion signal and the current motion signal to obtain the blurred image. We presented a configuration to remove . For example, in FIG. 6, which shows the relationship between a series of field signals and motion signals between corresponding fields, for field of interest i, fields i+l, i-1, i-2, i-3, i
The interpolation selection signal S, which instructs the selection of intra-field interpolation or inter-field interpolation, was obtained from the following formula 3 by performing logical operations on the motion signals a, b, c, and d obtained between -4 and 4. . In FIG. 6, A, A, and A indicate signals corresponding to the same positions on the screen of fields i-3, t-1, and i+1, respectively, and E, O, and force indicate signals corresponding to fields i-4, i+1, respectively. The corresponding signals of i-2,i are shown. The first term a-b is for removing the preceding blurred image (the shaded area of field i-1 in FIG. 4) of the moving object image, and d-c is for removing the subsequent blurring (field i+2 in FIG. 4). This is to remove the shaded area).

[Problem that the invention seeks to solve]

However, in this decision formula, when determining the movement of the field of interest (field i in Figure 4), it is assumed that there is no movement in field i-2 (that is, C is "L"), so
As shown in Fig. 6, when movement occurs every other field, C1d both become "H", and at this time a, b
are both “L”, so the interpolation selection signal S is “L” after all.
Therefore, there is a problem in that inter-field interpolation is selected even though there is movement in the field of interest.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an image signal conversion device that can realize a high-definition image without interpolation errors even for movements that occur every other field.

[Means for solving problems]

The image signal conversion device according to the present invention includes a first interpolation signal forming means for forming an interpolation signal from signals of different fields, a second interpolation signal forming means for forming an interpolation signal from within the same field, and a The apparatus includes interframe motion detection means for detecting motion and generating a motion signal, field memory for delaying a field of interest to be interpolated by one field, and holding means for retaining a motion signal from at least one field before. , the interpolation signal of the cylinder 1 and the second interpolation signal forming means is selected from the motion signal of a field temporally subsequent to the field of interest and the motion signal of the holding means.

[Effect]

With the above means, in the present invention, it is confirmed from each motion signal in which field the motion is occurring, so that the selection between intra-field interpolation and inter-field interpolation is appropriate, and the field before and after the field of interest is Even when movement occurs in both fields, intra-field interpolation can be selected accurately, and double images and blurred images that follow moving object images can be prevented.

〔Example〕

Hereinafter, the present invention will be described using one embodiment of the present invention with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention. The image signal X input to the input terminal 10 is delayed by one field each by the field memories 12, 14, and 16. Let the output of field memory 14 be X, and the output of field memory 16 be x4. The subtracter 18 subtracts the image signal X and the image signal X of one frame before, and the absolute value circuit 20 takes the absolute value of the output X of the subtracter 18 and supplies it to the comparison circuit 22. The comparator circuit 22 compares its input with a threshold Th, and when it is larger than Th, it outputs "H".
", and when it is less than Th, it outputs a "L" motion signal. This motion signal is sequentially delayed by one field by one field delay circuits 24, 26, and 28. The AND circuit 30 performs a comparison. The AND circuit 32 takes the AND of the output of the circuit 22 and the output of the delay circuit 26, and the AND circuit 32 takes the AND of the output of the delay circuit 24 and the output of the delay circuit 28. 32
Take the logical OR of the outputs of . The output of the OR circuit 34 becomes the interpolation selection signal S.

On the other hand, the image signal x3 delayed by a total of one frame in the field memory 12.14 is applied to the time compression circuit 36, and is also supplied to the line memory 38 and adder 40. 40 and the 1/2 coefficient circuit 42, the average is taken with the upper line, and the result is supplied to the selector 44 as an intra-field interpolation signal X. A signal x4 delayed by three fields from the field memory 16 is inputted to the selector 44 as an interfield interpolation signal, and the selector 44 selects the interfield interpolation signal x4 and the field according to the interpolation selection signal S from the OR circuit 34. Either one of the inner interpolation signals X is selected and supplied to the time compression circuit 36.

The time compression circuit 36 compresses the time axis of the original signal x and the interpolated signal x6 from the selector 44 to 1/2.

The signals are sequentially and alternately output to the output terminal 46.

Motion signals a, b, between consecutive fields illustrated in FIG.
c and d are the output of the delay circuit 26 and the comparison circuit 2, respectively.
2, the output of the delay circuit 28, and the output of the delay circuit 24.

Next, the operation of the circuit shown in FIG. 1 will be explained. In this embodiment, three stages of field memories 12, 14, and 16 are provided for the input image signal x1, and the field on which interpolation is performed is shifted one field before, and the motion signals a, b,
Interpolation of field i-1 (intra-field interpolation or inter-field interpolation) is determined based on c and d (FIG. 6). In the illustrated example, the interpolation selection signal S (output of the OR circuit 34) is 5=a-b+c-d, and the movement of point A (FIG. 6) in the field of interest i-1 is determined by the first term a-b. The presence or absence of the motion is checked, and the presence or absence of movement at point O (FIG. 6), which becomes the interfield interpolation signal, is checked in the second term c-d. Therefore, if there is movement at point O, intra-field interpolation is selected for field i-1, and the above-mentioned interpolation error does not occur.

In the illustrated example, a signal at a corresponding position in the previous field is used as the interfield interpolation signal, but the average value of the previous and subsequent fields may be used instead. In this case, d
Depending on the signal, it is possible to select either the previous field or this average value as the interfield interpolation signal.

That is, when the signal d is "L", the previous and subsequent fields (sixth
Since field i and fields 1-2 in the figure are both stationary, in this case, the average value of the previous and previous fields is used as the inter-field interpolation signal. This average value signal has a seven-fold improvement in S/N, and therefore, by performing such adaptive processing, the S/N of the interpolated signal can be improved.

(Effects of the Invention) As explained above, the present invention not only removes double images and blurred images that follow moving object images, but also provides accurate interpolation for movements that occur every other field. It is possible to present an image conversion device that can select signals and obtain high-definition images without interpolation errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a first embodiment of the present invention; FIGS. 2, 3, 4, and 5 are diagrams illustrating a method of selecting an interpolation signal by a conventional device and its effects; FIG. 6 is a diagram illustrating the relationship of motion signals between consecutive fields. 10-・Input terminal 12, 14.16・-Field・
Memory 18-- Adder 20- Absolute value circuit 22
-111 comparison circuit 24, 26.28-・Delay circuit 30
, 32-A N D circuit 3, l-OR circuit 3
6-Time compression circuit 38-Delay circuit 40-Adder
42 - 1/2 coefficient circuit 44 - Selector 46 - Output terminal Patent applicant Canon Co., Ltd. Figure 1 Figure 6 Figure 2 Figure 3

Claims (1)

[Claims] An image signal conversion device that inserts an interpolation signal into an image signal to form a higher-definition image signal, comprising: a first interpolation signal forming means that forms an interpolation signal from a signal of another field;
a second interpolation signal forming means for forming an interpolation signal from within the same field; an interframe motion detection means for detecting interframe motion and generating a motion signal; and a field for delaying the target field to be interpolated by one field.・Equipped with a memory and a holding means for holding a motion signal of at least one field or more earlier, and from the motion signal of a field temporally subsequent to the field of interest and the motion signal by the holding means, the first and An image signal conversion device characterized in that an interpolation signal of a second interpolation signal forming means is selected.