JPH08149499A - Image conversion device with gamma correction - Google Patents

Abstract

PURPOSE: To provide an expected flicker removal effect by providing 1/γ characteristics opposite to the γ correction characteristics of a display device for digital RGB signals and outputting those signals onto the display device after A/D conversion. CONSTITUTION: RGB input signals are inputted to a line buffer 1a, data for one line are temporarily stored, and one-line data to be delayed for one line are outputted. Then, the one-line data from the line buffer 1a are inputted to a line buffer 1b on the second stage and temporarily stored, and one-line data to be further delayed for one line are outputted. These digital RGB signals, RGB signals delayed for one line from the line buffer 1a and digital RGB signals delayed for two lines from the line buffer 1b on the second stage are respectively turned to 1/4, 1/2 and 1/4 levels through a two-bit shift register 1c, one-bit shift register 1d and two-bit shift register 1e and added by an adder 1f, and a new signal is generated by averaging signals for three lines.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image conversion apparatus having a flickerless processing section for removing flicker.

[0002]

2. Description of the Related Art Conventionally, when an image signal of a personal computer or the like is converted into a TV signal for interlaced scanning, a signal having a sharp brightness change in the vertical direction has a sharp brightness change in each field. Since the vertical synchronizing frequency becomes half and appears as flicker, various flicker removing circuits by two-dimensional or three-dimensional digital processing have been proposed to remove this flicker. For example, in the simplest binary averaging process, as shown in FIG. 5, the brightness levels of adjacent odd field lines and even field lines are averaged to create a new line,
As shown in FIG. 6, the luminance difference in the vertical direction is changed so that it is maximum and is 1/2 of the peak luminance. However, in actuality, when this signal is input to the display device and displayed, this effect is impaired due to the γ correction characteristic provided in the display device. For example, when displayed on a CRT display device, the γ correction value is generally γc = 2.2.
Assuming that the brightness B of the tube surface with respect to the signal voltage E is a constant K, it is expressed as K times E to the power of γc, and the curve of FIG. Assuming that the flicker removal processing reduces the signal level difference by half as described above, the difference in brightness actually displayed on the CRT screen surface becomes 1/5 as shown in FIG. Will not be obtained.

[0003]

SUMMARY OF THE INVENTION The present invention solves the problems described above and provides the expected flicker removing effect.
An object is to provide an image conversion device with correction.

[0004]

In order to solve the above-mentioned problems, the present invention has a flickerless processing section for removing flicker by averaging luminance differences between lines of a digital RGB signal input from a computer such as a personal computer. a .gamma. correction unit, a digital encoder unit for converting a TV signal of interlaced scanning, a D / A conversion unit for converting a signal from the digital encoder unit into an analog signal, and an output unit,
After the flicker removal processing, inverse γ correction is performed and then converted into a TV signal and output to the display device.

[0005]

With the above arrangement, the image conversion apparatus with γ-correction according to the present invention eliminates flicker by averaging the luminance differences between lines of a digital RGB signal input from a computer such as a personal computer and displaying it. The device is provided with a 1 / γ characteristic opposite to the γ correction characteristic of the device, and then converted to a TV signal for interlaced scanning, D / A converted, and then output to the display device.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image conversion device with gamma correction according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an image conversion device with γ correction according to the present invention. In the figure, reference numeral 1 is a flickerless processing unit, which has two stages of line buffers 1a and 1b and a plurality of shift registers 1.
c, 1d, 1e and an adder 1f, the signals of three lines are averaged to generate a new line signal. Reference numeral 2 denotes a γ correction unit, which stores two γ correction values for inputting a signal input from the flickerless processing unit to an address bus terminal and outputting data from a data bus terminal.
a and 2b, and a switching device 2c that is connected to the chip select terminals of the two ROMs and switches the output ROMs. A digital encoder 3 receives data from the γ correction unit 2 and converts it into a TV signal for interlaced scanning. Reference numeral 4 denotes a D / A converter which converts a digital signal from the digital encoder 3 into an analog signal. An output unit 5 adjusts the level, impedance and the like of the analog TV signal from the D / A conversion unit and outputs the adjusted signal to a display device or the like.

Next, the operation of the above configuration will be described. First, the input digital RGB signal is input to the line buffer 1a of the first stage to temporarily store data for one line, output one line data delayed by one line, and output one line data from the line buffer 1a. The data is input to the line buffer 1b at the stage, temporarily stored, and further outputs one line data delayed by one line. The input digital RGB signal, the first stage line buffer 1a
The digital RGB signal delayed by one line and the digital RGB signal delayed by two lines from the line buffer 1b in the second stage are respectively set in 2-bit shift registers 1c and 1c.
Bit shift register 1d, 2-bit shift register 1
to 1/4, 1/2, and 1/4 levels via e,
The adder 1f performs addition and averages the data of three lines. FIG. 2 is a diagram for explaining the operation of the flickerless processing unit.
The signals of the three input lines are averaged as described above,
Generating a new line signal. For example, the first line 1 of the new line data is obtained by multiplying the data of the first line of the original line by 1/4, the second line data by 1/2, and the third line data by 1/4. I am getting it. As shown in FIG. 3, the new line signal is smoothed by averaging the edge signals seen in the vertical direction by the signals of the three lines to make the maximum signal level difference 1 / the peak signal level.
I have set it to 2.

The line data averaged as described above is input to the address terminals of the ROMs 2a and 2b of the γ correction unit 2 and switched by the switch 2c according to the type of display device. For example, the display device is a CRT. For display devices,
The data of the first ROM 2a and the data of the second ROM 2b are output when the display device is an LCD. FIG. 4 shows γ characteristics stored in the first ROM 2a, and the γ is shown in FIG.
The reverse characteristic of the γ correction characteristic γc used in the CRT display device shown in FIG. 2 is shown. Since γc = 2.2, γ (= 1/1 /
γc = 1 / 2.2) = 0.45. First RO
Address data to be input from M2a (horizontal axis in Fig. 4)
The data (vertical axis in FIG. 4) corresponding to is output.

The data from the γ correction unit 2 is converted into an interlaced signal by the digital encoder 3 and then D /
The A converter converts the signal into an analog signal, the output unit generates a predetermined output signal level, outputs it with a predetermined output impedance, and inputs it to the display device.

[0010]

As described above, according to the image conversion device with γ-correction according to the present invention, the digital RGB signals input from a computer such as a personal computer are displayed by averaging the brightness differences between the lines to eliminate flicker and display. A 1 / γ characteristic opposite to the γ-correction characteristic of the apparatus is provided, and thereafter, the signal is converted into an interlaced scanning TV signal, D / A converted, and then output to the display apparatus. It is possible to provide an image conversion device with γ correction that can obtain a flicker removal effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image conversion device with γ correction according to the present invention.

FIG. 2 is a diagram for explaining an operation of a flickerless processing unit by 3-line processing.

FIG. 3 is a diagram for explaining the operation of a flickerless processing unit by 3-line processing.

FIG. 4 is a diagram showing a 1 / γ characteristic.

FIG. 5 is a diagram for explaining the operation of a flickerless processing unit by 2-line processing.

FIG. 6 is a diagram for explaining the operation of a flickerless processing unit by 2-line processing.

FIG. 7 is a diagram showing a γ characteristic used in a CRT display device.

FIG. 8 is a diagram showing a lightness signal of a tube surface when a vertical edge signal processed into a ½ level difference by a conventional image conversion device passes through a γ characteristic of a CRT display device.

[Explanation of symbols]

 1 Flickerless Processing Unit 1a First Stage Line Buffer 1b Second Stage Line Buffer 1c First Shift Register 1d Second Shift Register 1e Third Shift Register 1f Adder 2 γ Correction Unit 2a First ROM 2b Second ROM 2c switcher 3 digital encoder 4 D / A converter 5 output unit

Claims (4)

[Claims] 1. A flickerless processing unit for averaging luminance differences between lines to remove flicker from a digital RGB signal input from a computer such as a personal computer, and a γ correction unit.
It is composed of a digital encoder section for converting into an interlaced scanning TV signal, a D / A conversion section for converting a signal from the digital encoder section into an analog signal, and an output section. The image conversion device with γ correction is characterized in that the image signal is converted into a TV signal and output to a display device. 2. The image conversion device with γ correction according to claim 1, wherein the γ correction value of the γ correction unit is a reciprocal (1 / γ) of the γ correction value used for the display device. 3. The image conversion device with γ correction according to claim 1, wherein the γ correction unit is composed of a ROM that stores γ correction data. 4. The gamma correction unit is composed of a ROM for storing a plurality of gamma correction data and a switch, and the correction data is switched depending on a display device used. Image conversion device with γ correction.