JPH03245686A - Display device - Google Patents

Abstract

PURPOSE:To improve the resolution and to obtain an excellent picture by providing a filter limiting a band of a signal of picture information, a sample means sampling a signal at a speed being twice the highest frequency able to pass through the filter, and a drive means receiving an output of the sampling means, converting the output into a drive signal and controlling and driving the picture element of the display device to the display device. CONSTITUTION:A high frequency component of a video signal obtained by a video detection circuit 501 is eliminated by using a low pass filter 502 and the result is given to a sampling circuit 503. The cut-off frequency of the filter is suppressed at least nearly 1/2 of the sampling frequency by the sampling theorem. The low pass filter acts like outputting a mean value of waveform of signals inputted in a time corresponding to one period of the limit frequency and the limit frequency of the filter is decided depending how many picture elements are to be reduced. When an ideal low pass filter is employed, the picture element number and the limit frequency of the filter are proportional to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device for displaying images, such as a television.

The present invention relates to a display device that reproduces and displays a part of image information that is broken down into picture elements and transmitted. The object of the present invention is to obtain good image quality, especially to improve the resolution, when a part of the screen is extracted and reproduced from a display body with a limited number of picture elements, such as when displaying a screen of .

The following will explain the case where the present invention is applied to a small-sized television using a liquid crystal display, but the present invention is not limited to this, and may also be applied, for example, when displaying two channels of screens simultaneously on a CRT. Can be applied.

Conventional televisions mainly use cathode ray tubes to display images, and the number of picture elements displayed is constant regardless of the size of the screen. However, when trying to design a portable television device by making the display thinner and more compact, the depth of cathode ray tubes and the like cannot be reduced in principle, so it is better to use a thinner, lower power consumption display such as a liquid crystal display. convenient.

However, when trying to use a liquid crystal display for image display, for example, as shown in FIG. 1, the drive circuit requires a huge number of noises. -2...104-n, and also has the function of serial-parallel converting the video signal sent from the video detection circuit 100.

Normally charge coupled devices (C, C, D) etc. are often used, 102 is row signal line 103-1, 103-2...10
This is a driver for selecting and driving 3-m, and sequentially selects each row. Row and column synchronization is performed by a control circuit 106. 105-1゜1.105-1.2...
105-m and n correspond to each picture element, and one of them is illustrated in detail as shown in FIG. 2. That is, display segment electrodes 201 arranged in a matrix of a liquid crystal display.
It is composed of a switching transistor 202 and a capacitor 205, the gate of which is connected to the row signal 203, and the drain connected to the column signal 204.

Assuming that the current row is selected, the transistor 202 becomes conductive and the image signal ? At the same time, the capacitor 205 is charged with an electric charge corresponding to jl light from the column signal line 204, and a voltage is applied to the liquid crystal display segment electrode 201 to perform display.

Even if a row is subsequently unselected, the display segment is given a potential by the charge stored in the capacitor and the capacitance of the liquid crystal electrode itself, and the display effect is not lost until this charge is discharged. One or more switching transistors, capacitors, etc. are required for each picture element, and in order to display images using a thin liquid crystal display, a huge number of elements are required, which poses problems in terms of cost and manufacturing. Unfathomable.

Conventionally, in order to eliminate this drawback, a method has been adopted in which the volume of the device is reduced by sampling the pixels sent every few pixels to reduce the number of pixels. That is, a video signal as shown in FIG. 3(1) is periodically sampled and driven with a waveform as shown in FIG. 3(2).

Even if the number of picture elements on the screen is reduced by sampling in this way, it is thought to have almost no effect when the screen is small, but in reality it has the following drawbacks.

That is, when the sampling frequency and the frequency of the video signal become close to each other, this case is illustrated as shown in FIG. 4. The fact that the video signal contains frequency components as high as the sampling frequency means that when the screen is small, halftones must be displayed, because we want to display fine patterns that exceed the resolution of the display. Because of this, blurring should occur, resulting in an intermediate level --like display.

However, as is clear from FIG. 4, in the conventional sampling method, a striped pattern of the dipping liquid with a period much longer than the pattern intended to be displayed on the display is created due to the beat phenomenon.

The present invention, which eliminates the above drawbacks and provides good image quality even with a small number of picture elements, will be described below. When a video signal with a frequency component comparable to the sampling frequency is displayed on a small screen, the display resolution is greater than the resolution of the human eye, and the human eye often cannot discern the signal.
Midtones are identified as shown.

In other words, there is no need for such high frequency components in the video signal, so the high frequency components of the video signal obtained from the video detection circuit 501 can be removed using the low-pass filter 502 and transmitted to the sampling circuit 503 as shown in FIG. .

According to the sampling theorem, the cutoff frequency of the filter should be kept at least about 1/2 of the sampling frequency or less.

In this way, a low-pass filter has the function of outputting the average value of the signal waveform input during a period of time equivalent to one period of its limit frequency, and the limit frequency of this filter is determined by how many picture elements it reduces to. be able to.

Considering an ideal low-pass filter, the number of picture elements and the limit frequency of the filter are directly proportional.

As described above, the number of picture elements of an image signal sent by a television etc. can be reduced by the method described above, and the cost of the display body and display drive circuit can be lowered, while the image resolution is not extremely deteriorated. Small size, low power consumption,
This effect is exhibited in small portable televisions and the like that use liquid crystal displays that take advantage of their thin characteristics.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing the display portion of a television using a conventional liquid crystal display. FIGS. 3 and 4 are diagrams showing sampling of video signals. FIG. 5 is a block diagram showing a display device according to the present invention. 100... Video detection circuit 101... Column signal driver 102... Row signal driver 103-1, 103-2... 103-m... Row signal line 104-1, 104-2... 104-n...column signal lines 105-1.1, 105-1.2...105-m,
n...Picture element 201...Display segment electrode 202...Switching transistor 203...Row signal line 204...Column signal line 205...Capacitor 501...Video detection circuit 502...Low pass Filter 503...sampling circuit

Claims (1)

[Claims] 1. Reproduce image information that is broken down into picture elements and sent sequentially,
In a display device for displaying, a filter for limiting the band of the signal of the image information, a sampling means capable of sampling at a speed of at least twice the highest frequency that can pass through the filter, and converting the output of the sampling means into a corresponding drive signal. A display device comprising a driving means for controlling and driving picture elements of the display device.