JPH02164187A - Signal interpolation method - Google Patents

Abstract

PURPOSE:To form an interpolation signal not causing flicker and deterioration in resolution by applying average interpolation to a low frequency component of an original signal through a delay line for a prescribed delay time and applying pre-value interpolation to a high frequency component of an original signal. CONSTITUTION:The original signal is inputted to an input terminal 20 and the original signal is fed to a low pass filter(LPF) 22 for low frequency component output and a high pass filter(HPF) 24 for high frequency component extraction. An output of the LPF 22 fed to a 1st input of an adder circuit 30 via a 1H delay line 24 and a 1/2 circuit 28 and fed to a 2nd input of the adder circuit 30 via a 1/2 circuit 32. The output of the HPF 24 is fed to a 3rd input of the adder circuit 30, the adder 30 sums the 1st, 2nd and 3rd input signals and outputs the sum to an output terminal 34. The 1/2 circuits 28, 32 halve the amplitude of the input signals. Thus, the adder circuit 30 applies average interpolation to a low frequency component from the LPF 22 and applies pre- value interpolation as to the high frequency component from the HPF 24.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal interpolation method, and for example, to a method of interpolating between original signals with a similar signal, such as when converting a field signal into a pseudo frame signal. .

[Prior Art] The interpolation methods for converting a field signal into a pseudo frame signal are basically a pre-value interpolation method in which the first field is converted into a second field, and a horizontal scanning method in which the first field is adjacent to the first field. In the average interpolation method in which the average value of the signal is used as the second field, and in the previous value interpolation method, flicker occurs in the reproduced video because the interpolated signal is the same as the original signal. Sometimes. In particular, flicker in low frequency components causes image deterioration. On the other hand, average interpolation does not cause flicker, but because it uniformly averages the signal from low to high frequencies, high frequency components are lost and the reproduced video may lack sharpness. In particular, the resolution of images without vertical correlation is significantly reduced.

For example, assume that the signal in one horizontal scanning period of a video signal is as shown in FIG. 2A, and the signal in the next one horizontal scanning period is as shown in FIG. 2B. The average interpolation circuit basically operates during one horizontal scanning period (I
The delay line 10 shown in FIG. Actually, after addition by the adder circuit 12, the signals are multiplied by 1/2, or each signal before addition is halved, but this is not shown since it is not an essential problem. At the time when the signal shown in FIG. 2A is applied from the delay line 10 to the addition circuit 12, the signal shown in FIG. , due to the phase shift between the high frequency components of signal A and signal B, a signal with a significantly reduced resolution as shown in FIG. 2G is obtained.

Therefore, the present invention provides a signal interpolation method that does not cause flicker and does not cause resolution deterioration.The signal interpolation method according to the present invention adaptively changes the interpolation method according to the band of the original signal. Features. Further, the present invention is characterized in that average interpolation is performed on the low frequency components of the original signal using a delay line having a predetermined delay time, and previous value interpolation is performed on the high frequency components of the original signal.

[Operation] In this way, by changing the interpolation method according to the signal band, it is possible to perform preferable interpolation according to the signal. Also,
By changing the method of forming interpolation signals for low-frequency components and high-frequency components, neither average interpolation problems nor previous value interpolation problems occur. Therefore, no flicker occurs, and there is no significant deterioration in resolution.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a first example circuit implementing the method of the invention.

An original signal is input to the input terminal 20, and the original signal is passed through a low pass filter (LPF) 22 for extracting low frequency components and a high bass filter (HPF) 2 for extracting high frequency components.
4.

The output of the LPF 22 is applied to the first power of the adder circuit 30 via the IH delay line 24 and the 1/2 circuit 28, and is also applied to the second power of the adder circuit 30 via the 1/2 circuit 32. Ru. The output of the HPF 24 is applied to the third human power of the adding circuit 30, and the adding circuit 30 adds the signals of the first, second, and third human power and outputs the result to the output terminal 34. 1/2 circuit 2
8.32 is a circuit that halves the amplitude of the input signal. Therefore, the adder circuit 30 performs average interpolation for the low frequency component from the LPF 22, and performs previous value interpolation for the high frequency component from the HPF 24.

Assume that after signal A1 in FIG. 2, signal B is applied to the input terminal 20 as an original signal. Signal C in FIG. 2 shows the low frequency component of signal A, signal I shows the low frequency component of signal B, and signal E shows the high frequency component of signal B. At the time when the signal C (actually 1/2 signal) is input from the 1/2 circuit 28 to the first input of the adder circuit 30, the signal D (from the 172 circuit 32) is input to the second input of the adder circuit 30. In reality, 1/2 of that signal) is input, and the third input of the adder circuit 30 receives the signal E.
is input. As a result, the adder circuit 30 outputs the signal shown in FIG. 2F. Since low-frequency components are average interpolated, flicker does not occur, and as can be seen from the comparison with signal G, the resolution has not deteriorated.

In this circuit, only low frequency components are applied to the IH delay line for average interpolation, so the band of this delay line may be narrow. Therefore, for example, when a COD element is used in this delay line, the frequency of the COD driving clock may be low, and power consumption can be reduced. Moreover, it becomes easy to employ a glass delay line.

3, 4 and 5 show further circuit examples implementing the method according to the invention. Note that illustration of the 1/2 circuit for average interpolation is omitted.

FIG. 3 shows an example in which the low frequency component is extracted by subtracting the high frequency component from the original signal, which eliminates the need for an LPF. The original signal at the input terminal 36 is applied to the first input of the adder circuit 40 via the HPF 38. The original signal of the input terminal 36 is applied to one input of the subtraction circuit 42, and the output of the HPF 38 is applied to the other input. Subtraction circuit 4
The output of No. 2 is a low frequency component of the original signal, which is applied to the second input of the adder circuit 40, and is also applied to the third input of the adder circuit 40 via the IH delay line 44. After all, the output of the adder circuit 40 corresponds to the original signal obtained by performing previous value interpolation on the high frequency components and performing average interpolation on the low frequency components.

FIG. 4 shows an example in which a high frequency component is extracted by subtracting the low frequency component from the original signal, contrary to the case of FIG. 3. In this example, HPF is not required. The original signal at input terminal 46 is applied to the first input of adder circuit 52 via LPF and IH delay line 50 . The output of the LPF 48 is applied to one input of the subtraction circuit 54, and the original signal of the input terminal 46 is applied to the other input. The output of the subtraction circuit 54 becomes the high frequency component of the original signal. The output of the LPF 48 is applied to the second input of the addition circuit 52, and the subtraction circuit 5 is applied to the third input.
4 outputs are applied. The first and second human inputs of the adding circuit 52 result in average interpolation for low frequency components, and the third human input of the adding circuit 52 results in previous value interpolation for high frequency components.

FIG. 5 shows an example in which the circuit is further simplified and subtraction circuits 42 and 54 for extracting low-frequency components or high-frequency components are not required. The original signal at the input terminal 54 is applied to one input of the adder circuit 60 via the LPF 56 and the IH delay line 58. The other input of the adder circuit 60 is applied with the original signal of the input terminal 54 . Low-frequency components passing through LPF56,
An average interpolated signal is formed by the low-frequency components of the signal that does not pass through the LPF 56, and a previous value interpolated signal is formed by the high-frequency components of the signal that does not pass through the LPF 56. In this example, 1/2 processing for average interpolation is performed. Although it also affects high-frequency components, it does not have much of a visual impact.However, with this configuration, delay compensation, which is not necessary in FIGS. 3 and 4, must be performed.

In the circuit of FIG. 3, a delay line 44 with a wide band must be used, but in the circuits of FIGS. 4 and 5,
The band of the delay line 50.58 may be narrow, for example COD
When implemented using a device, the drive clock frequency can be lower, and therefore, power consumption can be reduced, and a glass delay line can also be used.

FIG. 7 shows a block diagram of the overall configuration of a reproducing apparatus to which the signal interpolation method of the present invention is applied. In FIG. 7, 80 is a magnetic disk which is a recording medium on which an image signal is modulated and recorded. A plurality of concentric tracks are formed on the magnetic disk 80, and the image signal of one field is recorded in the track 1 and 2. recorded. A PG bin 98 is also embedded in the magnetic disk 80 to indicate its rotational state.

82 is a playback head that plays back the image signal from the disk 80; 84 is a playback amplifier that amplifies the output of the head 82; 88
90 is an interpolation circuit corresponding to the circuits shown in FIGS. 1, 3 to 5, and 92 selects the output of the interpolation circuit 90 or the output of the demodulation circuit 88. A selector switch that outputs the output to the output terminal OUT,
93 is a detection head for detecting the position of the PG pin 98; 94 is a PG amplifier for amplifying the output of the head 93; 96
is a waveform shaping circuit that shapes the waveform of the output of the PG amplifier 94 and generates a pulse whose period is two revolutions of the disk 80.

By applying the signal interpolation method of the present invention to a reproduction device as shown in FIG. 7, it is possible to form an interpolation signal that does not cause flicker or deterioration of resolution, and reproduces extremely high-quality images. become able to do.

Although analog signals have been considered in the above description, the present invention is also applicable to digital signals. In that case,
Of course, digital filters will be used as the HPF and LPF. Further, in the above embodiment, the method of the present invention is used when converting a field image into a frame image, but the present invention is not limited to this, and can be similarly applied to dropouts in reproduced image signals. .

[Effects of the Invention] As can be easily understood from the above description, according to the present invention, it is possible to form an interpolation signal that does not cause flicker and does not cause resolution deterioration.

[Brief explanation of the drawing]

FIG. 1 is a first circuit example implementing the method of the present invention, FIG. 2 is a waveform diagram of the circuit of FIG. 1, and FIGS. 3, 4, and 5 are other circuit examples of the present invention. FIG. 6 shows an example of a conventional circuit using the average interpolation method, and FIG. 7 shows a block diagram of a reproducing apparatus to which the present invention is applied. 12.30, 40, 52, 60: Addition circuit 20°36
．． 46, 54: Input terminal 42, 54: Subtraction circuit diagram

Claims (2)

[Claims] (1) A signal interpolation method characterized by adaptively changing the interpolation method according to the band of the original signal. (2) A signal interpolation method characterized by performing average interpolation on the low frequency components of the original signal using a delay line with a predetermined delay time, and performing previous value interpolation on the high frequency components of the original signal.