JPS61184059A - Flair correction filter - Google Patents

Abstract

PURPOSE:To save an inverting circuit and to miniaturize the titled filter by using a vertical flair correction recursive filter and a horizontal flair correction recursive filter in common for a field inverting circuit and a line inverting circuit. CONSTITUTION:In the flair correction filter, two flair correction recursive filters 11, 12 are arranged in cascade before and after the field inverting circuit 13 and the field inverting circuit 14 is arranged at the final stage. The filter 11 consists of the vertical flair correction recursive filter 11a and the horizontal flair correction recursive filter 11b connected in series and the filter 12 is constituted similarly. The circuit 13 is constituted of a field memory writing a picture signal for one field's share and reading a picture signal for one field's share in the order reverse to the write. thus, the circuit 13 acts as the field inverting circuit arranged between the filters 11a and 12a and functions as the line inverting circuit placed between the filters 11b and 12b.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a flare correction filter used in high-definition television receivers and the like.

In high-definition television systems that use a large projection type projector as a display device, flare correction and contour correction are performed in advance using a digital filter before the display device in order to prevent flare and decrease in contrast. There may be cases.

A prior art image quality improvement device that performs flare and contour correction using a digital filter is disclosed in a prior patent application entitled “Color Television Image Quality Improvement Device” (Japanese Patent Application No. 1988-2088)
46, 210313-210319).

One of the flare correction digital filters used in the above-mentioned prior art image improvement circuit consists of a vertical flare correction filter 1 and a horizontal flare correction filter 2 connected in cascade, as shown in FIG. . Each filter 1.2 for flare correction uses a recursive filter (recursive filter) in order to avoid increasing the scale of the circuit when it is configured with a transversal filter.

Each flare correction filter 1.2 passes the image signal through the recursive filter twice, and then reverses the time axis and re-inverts the time axis in order to improve the phase distortion caused by passing the image signal through the recursive filter only once. By passing the signal through a recursive filter, phase distortion is canceled out, and the time axis is finally returned to its original state. Therefore, the vertical flare correction filter l requires two field inversion circuits 1b and lb' for time axis inversion in addition to the recursive filters la and la'' for vertical flare correction. The correction filter 2 requires two line inversion circuits 2b and 2b' for time axis inversion in addition to horizontal flare correction recursive filters 2a and 2a'.

Problems to be Solved by the Invention The flare correction filter of the prior art requires a total of four time axis inversion circuits, two each for vertical flare and horizontal flare correction, and as a result, the flare correction filter However, there is a problem in that it is expensive and large in size.

Structure of the Invention Means for Solving the Problems The flare correction filter of the present invention which solves the problems of the prior art described above has the following features: By sharing a time axis inversion circuit between the vertical flare correction filter and the horizontal flare correction filter. , two line inverting circuits are saved, and it is constructed to realize cost reduction and miniaturization.

Hereinafter, the effects of the present invention will be explained in detail by way of examples.

Embodiment FIG. 1 is a block diagram showing the configuration of a flare correction filter according to an embodiment of the present invention.

This flare correction filter combines two flare correction recursive filters 11 and 12 with a field inversion circuit 13.
The field inverting circuit 14 is arranged in a column before and after the field inversion circuit 14, and the field inversion circuit 14 is arranged in the final stage.

The upstream flare correction recursive filter 11 includes vertical flare correction recursive filters lla connected in series.
and a horizontal flare correction recursive filter Ilb. Similarly, the subsequent flare correction recursive filter 12 includes a vertical flare correction recursive filter 12a and a horizontal flare correction recursive filter 12b connected in series.

The field inversion circuit 13 is composed of a field memory in which one field's worth of image signals is written and one field's worth of image signals is read out in the reverse order of writing. This field inversion process can be explained using FIG.
The image signal once written in the memory is read out in the reverse direction from the last line in the field to the first line in the direction indicated by the arrow. As is clear from the figure, when inverting the time axis of the image signal in units of one field, time axis inversion (line inversion) is also performed in units of one line.

Therefore, the field inversion circuit 13 functions as a field inversion circuit placed between the vertical flare correction recursive filters lla and 12a, and at the same time functions as a line inversion circuit placed between the horizontal flare correction recursive filters llb and 12b. will also function.

Vertical flare correction recursive filter lla in Figure 1
and 12a are adder circuits 22. and 12a, as illustrated in FIG.
23 and 24, ■ line delay circuit 25, 26 and 27
and coefficient circuits 28, 29, and 30, performs vertical flare correction filtering on the image signal supplied to the input terminal 21, and outputs it to the output terminal 31.

Recursive filter llb for horizontal flare correction in Figure 1
and 12b are similar to the recursive filter for vertical flare correction illustrated in FIG. 3, except that a delay circuit for one sampling period is used in place of the one-line delay circuits 25 to 27 in FIG. The structure is as follows.

Above, we have shown an example of a configuration in which a field inversion circuit is placed in the final stage to restore the time axis inversion and output, but in the vertical/horizontal scanning circuit in the stage after this flare correction circuit, the time axis is inverted while the vertical/horizontal If the configuration is configured to perform scanning, the field inversion circuit 14 at the final stage can be omitted. That is, instead of omitting the field inversion circuit 14,
It is sufficient to generate a vertical deflection current and a horizontal deflection current of inverse sawtooth waves in a subsequent scanning circuit, and to scan each field in opposite directions in both the vertical and horizontal directions, as shown by the arrows in FIG.

As explained in detail in ``Effects of the Invention'', the flare correction filter of the present invention has a configuration in which a field inversion circuit and a line inversion circuit are commonly used. The number of circuits can be reduced, making it cheaper, smaller, faster, and more reliable.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the configuration of a flare correction filter according to an embodiment of the present invention, FIG. 2 is a conceptual diagram illustrating that field inversion processing also serves as line inversion processing, and FIG. 3 is the recursive for vertical flare correction shown in Figure 1.
FIG. 4 is a circuit diagram showing an example of the structure of filters lla and 12a, and FIG. 4 is a block diagram showing the structure of a prior art flare correction filter. 11.12... Recursive filter for flare correction, l
la, 12a... Recursive filter for vertical flare correction, llb, 12b... Recursive filter for horizontal flare correction.
Filter, 13.14...Field inversion circuit. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Claims] 2 consisting of a series-connected recursive filter for vertical flare correction and a recursive filter for horizontal flare correction.
A flare correction filter characterized in that a number of flare correction recursive filters are connected in series before and after a field inversion circuit.