JPH0832024B2 - Image signal converter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for converting interlaced scanning of image signals such as television signals into non-interlaced scanning.

[Conventional technology and its problems]

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 line of one field is doubled, for example.

How to generate an interpolating signal between scanning lines is a problem for doubling the number of scanning lines. For example, in-field interpolation using an average value of two adjacent lines in the same field as another interpolating signal, Inter-field interpolation, which uses the corresponding signal of the field as an interpolation signal,
A method of switching according to the movement of the image has been proposed.
In this method, the accuracy of motion detection of the object image is an important factor that affects the image quality, but in general, the presence or absence of motion is determined by whether or not a significant difference has occurred in the difference signal (frame difference) between the front and rear fields. There is. However, in the current field, a significant difference may not appear in the difference signal between the preceding and following fields even in the moving area, and in such a case, a remarkable image quality deterioration such as a double image may occur.

This image quality deterioration will be described with reference to FIGS. (1) to (6) of FIG. 5 are (1) to (6) of FIG.
Corresponding to. In FIGS. 5 and 6, the shaded area indicates the selection of the inter-field interpolation. Now, the object image indicated by the thick line that has been stationary at the position (2) in the field i−1 moves from the field i to to the field i +
It is assumed that the vehicle is stationary at the position (4) with 1. At this time, if motion detection is performed using the difference signal between the front and rear fields,
In the area indicated by the field i in FIG. 5, the intra-field interpolation is selected because a significant difference occurs in the frame difference in FIG. 6, but the frame difference does not cause a significant difference. The inter-field interpolation signal is selected regardless of the area, and the signal corresponding to the background image of the previous field is interpolated in the area of FIG. 5 to cause double image interference.

Further, since the motion is generated only in the field i and the fields i-1 and i + 1 are stationary, the inter-field interpolation is possible, but the motion is detected in the motion detection based on the frame difference. Since the field cannot be determined, the field i-1 and the field i + 1 are interpolated in the field, and there is a disadvantage that an unnatural image of a low-resolution image (blurred image) following the moving object becomes an image. .

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an image signal conversion device that overcomes the above-mentioned drawbacks and that can obtain a high-definition non-interlaced image without a double image disturbance and a blurred image that follows a moving object. .

[Means for solving problems]

An image signal converting apparatus according to the present invention includes a first forming unit that forms an interpolation signal from a signal of the same field, a second forming unit that forms an interpolation signal from a signal of a previous field, and an interpolation from a signal of a subsequent field. A third forming means for forming a signal, a fourth forming means for forming an interpolation signal from the signals of the front field and the rear field, and a signal of the previous field preceding the field of interest for forming the interpolation signal,
And a determination unit that determines a motion of an image by calculating a difference signal between adjacent fields between a signal of a subsequent field following the field of interest and a signal spatially located above and below the interpolation scanning line. Any of the interpolation signals is appropriately selected based on the result of this determination.

[Action]

The double image disturbance is caused by the fact that the motion of the image cannot be detected in principle because the motion of the image is detected by the frame difference. Further, in the blurred image, it is not possible to specify which of the two fields for which the frame difference is obtained is in motion, and the signal of the previous field is uniformly used as the inter-field interpolation signal. Caused by. Therefore, the present invention focuses on the field difference, removes the double image interference by utilizing the strong inter-field correlation in the case of a stationary surface, and removes the tracking of the blurred image. Not only the difference between the field of interest and the previous field, but also the difference between the field of interest and the field after that, and based on the result of motion determination based on these, the inter-field interpolation signal is switched appropriately to follow the double image or the moving object image. It is possible to effectively prevent blurring.

〔Example〕

Hereinafter, the present invention will be described using an embodiment of the present invention with reference to the drawings. In the present embodiment, it is assumed that the input image signal constitutes one frame with 525 lines.

FIG. 1 is a block diagram of an embodiment of the present invention. Image signal x ₁ input to input terminal 10 is the field memory
The 12 line memory 14 and the field memory 16 delay 262 lines, 1 line and 262 lines, respectively.
The output of the field memory 12 is x ₂ , the output of the line memory 14 is x ₃ , and the output of the field memory 16 is x ₄ .

The subtractor 18 subtracts the signal x ₂ from the image signal x ₄ 263 lines before it, and the absolute value circuit 20 takes the absolute value of the output of the subtractor 18 and supplies it to the comparison circuit 22. The subtracter 24 subtracts the image signal x ₃ from the image signal x ₄ one field (actually 262 lines) before that, and the absolute value circuit 26 takes the absolute value of the output of the subtractor 24 and compares it with the comparison circuit 28. Supply to.
The comparators 22 and 28 compare their inputs with a threshold value Th and output difference determination signals (H when Th is larger than Th and L when Th is less than Th) b, a. The AND circuit 30 obtains the logical product of the outputs b and a of the comparison circuits 22 and 28, and outputs the interpolation selection signal S ₁ .

The subtractor 32 outputs the image signal x ₁ and its 1 field (actually 26
Subtracting from the previous image signal x _{2 (} for two lines), the absolute value circuit 34 takes the absolute value of the output of the subtractor 32 and supplies it to the comparison circuit 36. The subtractor 38 subtracts the image signal x _{1 from} the image signal x ₃ one field before (actually 263 lines), and the absolute value circuit 40 takes the absolute value of the output of the subtractor 38 and compares it.
Supply 42. The comparators 36 and 42 have their inputs at the threshold Th.
And a difference judgment signal (H when larger than Th, L when smaller than Th) c, d is output. In the comparator circuits 36 and 42, the threshold T
Note that the input side of h is the opposite. The AND circuit 44 calculates the logical product of the outputs c and d of the comparison circuits 36 and 42 and outputs the interpolation selection signal S ₂ .

On the other hand, the adder 46 adds the same x ₄ to the video signal x ₁ value to obtain 1/2
The coefficient circuit 48 multiplies the sum by 1/2 and supplies the inter-field interpolation signal (average value of the preceding and following fields) x ₅ to the selector 50. The adder 52 adds the same x ₃ to the video signal x ₂ to obtain 1/2
The coefficient circuit 54 multiplies the sum by 1/2 and supplies the intrafield interpolation signal x ₆ to the selector 50. In addition to the selector 50, input video signal x ₁ and 1 frame (525 lines)
The video signal x ₄ delayed by the amount is supplied, and the interpolation selection signals S ₁ and S ₂ are applied as control signals.

The selector 50 outputs 4 according to these interpolation selection signals S ₁ and S _2.
One of the interpolated signals is selected and supplied to the time compression circuit 56. FIG. 7 shows the relationship between the interpolation selection signals S ₁ and S ₂ and the selected interpolation signal x ₇ . The time compression circuit 56 divides the time axis of the original signal x ₃ and the interpolation signal x ₇ from the selector 50 by 1/2.
And output to the output terminal 58 alternately in sequence.

Next, the difference determination signals a, b, and
The operation of the circuit shown in FIG. 1 will be described with reference to FIG. 2 showing the relationship between c, d and the video signals x ₁ , x ₂ , x ₃ , x ₄ . The difference determination signals a, b, c, d and the video signals x ₁ , x ₂ , x ₃ , x ₄ in FIG. In Fig. 2, the vertical axis indicates the vertical direction on the screen,
The horizontal axis represents time. Therefore, the vertically aligned signals are
They are in the same field. Here, which interpolation signal is used to interpolate between the video signal x ₂ and the video signal x ₃ of the field i will be described.

It is now assumed that the field i + 1 is "moving". Since there is almost no correlation between the field i and the field i + 1, the absolute value of (x ₁ −x ₂ ) is larger than Th, the difference determination signal c becomes H, and (x ₁ −x ₃ ) absolute value. greater than Th also difference judging signal d also becomes "H", as a result, the interpolation selection signal S ₂ is "H". Fields i-1 and i
When both are "stationary", the correlation between the fields i-1 and i is strong, and even if an image edge exists between x ₂ and x ₃ , (x ₄ −x ₂ ) Absolute value of or (x ₄ −x ₃ )
It is considered that either one of the absolute values of is smaller than Th, so the interpolation selection signal S ₁ becomes L. Therefore, as shown in FIG. 7, the selector 50 outputs the signal x ₄ as the interpolation signal x ₇ .

Conversely, if the field i-1 is "moving", the fields i, i
For +1 "stationary", S ₁ is H, S ₂ is L, the selector 50 outputs the signal x ₁ as the interpolation signal x _7.

When the fields i−1, i, i + 1 are all “stationary”, the inter-field correlation is strong, so that the interpolation selection signals S ₁ and S ₂ are both L, and the selector 50 causes the average value (x ₁ + x ₄ ) / 2 is output as the interpolation signal x ₇ .

When the field i is “moving”, it is between the field i−1 and the field i and between the field i and the field i +.
Since the correlation is weak between 1, the determination signals a, b, c, d are all H, the interpolation selection signals S ₁ , S ₂ are both H, and the selector 50 selects (x ₂ + x ₃ ) / 2 is the interpolation signal x ₇
Output as

In this embodiment, how the image on the screen is displayed is shown in FIG. 3, and the manner of interpolation in consecutive fields is shown in FIG. In FIG. 3, the shaded area indicates the inter-field interpolation area, the portion designated as the front F interpolation indicates that the interpolation signal is taken from the front field, and the portion indicated as the rear F interpolation indicates that the interpolation signal is taken from the rear field. . Fourth
In the figure, ○ indicates a normal scanning line signal, ▲ indicates interpolation by the in-field signal, ● indicates interpolation by the average value of the signals of the preceding and following fields, ■ indicates interpolation by the signal of the previous field, and ◆. Indicates interpolation by the signal of the rear field. The arrow in FIG. 4 indicates which scanning line signal is used as the interpolation signal.

As can be seen from FIG. 3, in the present embodiment, the intra-field interpolation is selected only for the field i in which motion has occurred, and the double image as described in FIG. 5 does not occur. . Also, as can be seen from FIG. 4, when no motion occurs in three consecutive fields, the central field is interpolated by the average between the preceding and following fields. Since the S / N ratio of the signal is improved by the interpolation using the average value, the S / N ratio of the entire image is also improved. Since the image signal usually has a static area in most cases, the interpolation by the average value of the front and rear fields is extremely effective.

〔The invention's effect〕

As can be easily understood from the above description, according to the present invention, it is possible to remove an image having a low resolution that follows a moving object image and realize scanning line conversion without deterioration of an image edge portion or double image. I can.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is
Shows field differential is obtained by the circuit of FIG. 1 in 3 consecutive fields determination signal a, b, c, the relationship between d and the video signal _{x 1, x 2, x 3} , x 4. FIG. 3 is a diagram showing what kind of interpolation is performed on the screen by the movement of an object according to the present invention, and FIG. 4 is what kind of interpolation is adopted according to the present invention between consecutive fields. It is a figure which shows whether it is performed. FIGS. 5 and 6 are diagrams for explaining a method of selecting an interpolation signal by the conventional device and its effect, and FIG. 7 is an interpolation selection signal S ₁ , S ₂ and an interpolation signal x ₇ selected in FIG. It is a figure which shows the relationship with. 10 ... Input terminal, 12 ... Field memory, 14 ... Line
Memory, 16 ... Field memory, 18, 24, 32, 38 ... Subtractor, 20, 26, 34, 40 ... Absolute value circuit, 22, 28, 36, 42 ... Comparison circuit, 30, 44 ... AND circuit, 46 , 52 ... Adder, 48, 54 ... 1/2 coefficient circuit, 50 ... Selector, 56 ... Time compression circuit, 58 ... Output terminal

Claims (1)

[Claims] 1. An image signal conversion device for forming a higher definition image signal by inserting an interpolation signal into an image signal, comprising first forming means for forming an interpolation signal from signals of the same field, and a previous field. Second to form an interpolation signal from the signal of
Forming means, a third forming means for forming an interpolation signal from the signal of the rear field, a fourth forming means for forming an interpolation signal from the signal of the previous field and the rear field, and a field of interest for forming the interpolation signal. The difference signal between adjacent fields between the signal of the preceding field preceding the signal of the preceding field, the signal of the following field following the target field, and the signal spatially above and below the interpolation scan line is calculated, and the image movement is calculated. An image signal conversion apparatus comprising: a determination unit that determines whether or not any of the interpolation signals is appropriately selected based on the determination result.