JPS6348979A - Contrast adjustment device for crt - Google Patents

Abstract

PURPOSE:To form a picture of high quality by adjusting the reference input level of a DA converter for converting a digital video signal into an analog signal and adjusting the contrast of the display video of a CRT. CONSTITUTION:A video signal stored in a frame memory 10 is read by an output 18 for every decomposed color under the control of a reading control part 16. At the time of converting into the analog signal by the DA converter 16, an analog signal level is applied with the contrast according to a reference voltage set to the reference input level 22 by a digital code switch 32. Thereby, the contrast of the picture outputted to the display screen 40 of the CRT 36 can be adjusted. This contrast adjustment is carried out to the digital signal, so that a high stability can be obtained.

Description

Detailed Description of the Invention 3. Detailed Description of IJI Technical Field The present invention relates to cathode ray tube equipment, more specifically, cathode ray tube (CR) equipment.
The present invention relates to a contrast adjustment device for adjusting the contrast of an image displayed in T).

BACKGROUND ART The contrast of a displayed image on a CRT has been adjusted, for example, by adjusting the gain of an amplifier that amplifies the image signal input to the cathode of the CRT. Conventionally, adjustment circuits for this purpose have been realized using analog circuits.

For example, an image recording device has been proposed that reads out a video signal recorded on a video floppy, displays it as a visible image on a CRT, forms an image on photographic paper using a lens optical system, and obtains a hard copy of the image. . Still images obtained as such hard copies are generally
Higher image quality is required than L and G images. therefore,
Unless the contrast of the displayed image is properly adjusted and the adjusted state is not stable, it is not possible to obtain a hard copy of a still image with good image quality.

However, the contrast with conventional analog circuits, i1
J-adjustment has the disadvantage that high stability cannot be obtained due to drift of circuit elements. In addition, in order to realize a highly stable brightness adjustment circuit, high-quality elements must be used.
Therefore, equipment prices will rise.

]-1 Objectives The objective of II is to provide a contrast adjustment device for a CRT which can eliminate the drawbacks of the prior art and perform stable contrast adjustment with a simple configuration.

A CRT contrast adjustment device by IJI includes a signal conversion means for receiving a digital video signal and converting the video signal into a corresponding analog signal within a level range corresponding to a reference input; It has an electrode tube means for visually displaying 12 images represented by the analog signal in response to the analog signal outputted by the means, and a reference input means for adjustablely generating a reference input and providing the reference input to the signal converting means. ,
By adjusting the reference input means, the contrast of the image represented by the analog signal is adjusted.

DESCRIPTION OF EMBODIMENTS Next, embodiments of a CRT contrast adjustment device according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment in which the present invention is applied to a portrait recording device that reads video signals stored in a memory and creates a hard copy of the image. The wooden neck has a frame memory IO, which is a temporary storage device in which one frame or field of video signals recorded on a magnetic recording medium such as a video floppy is read in the form of a digital signal and stored. It is. In the wooden embodiment, the twelve image signals are color video signals separated into three primary color signals. Which signal format is used is not essential to the present invention. Its read data output 12 is connected to a digital-to-analog converter W(OAIC) +4.

The digital-to-analog converter 14 receives a clock CL supplied via a signal line 20 from a readout synchronization section 18, which will be described later.
This is a signal conversion circuit that converts digital data at input 12 into a corresponding analog signal in response to K, and outputs this from an output (OUT) 18. Digital-to-analog converter 14 has a reference input terminal 22 to which 2! An analog signal having a level corresponding to the value obtained by multiplying the i-band voltage VREF by the value of the digital signal at the input 12 is output from the output 18. In other words, the range in which the analog pressure of the output 18 changes, that is, the dynamism and r range, can be changed according to the reference voltage VREF. For example, when the reference voltage VREF becomes high, the dynamic range expands, and when the reference voltage VREF becomes low, it becomes more rounded. As the digital φ analog converter 14, for example, model TDC:1018 manufactured by TRw is applied to the case.

The input terminal 22 of the digital to analog converter 14 is connected to the analog output terminal 28 of another digital to analog converter 26 via a voltage divider 24 consisting of resistors R1 and R2. The analog converter 26 has a digital input 30, and the input 30 is also a conversion circuit that converts the input digital data into a corresponding analog signal and outputs it to the output 2B.The input 30 is connected to the digital code switch 32. The digital code switch 32 is a coding switch for manually setting the value of the reference voltage VREF of the digital-to-analog converter 14, and generates the set value at the output 30 in binary code. do.

As will be seen from now on, the value of the reference voltage VREF manually set with the switch 32 is input from its output 30 to the Digimol Analog Converter 26 in binary code.
The converter 26 converts it into a corresponding analog voltage and outputs it to its output 28. This analog voltage is divided by a voltage divider 24, and a reference voltage VR according to the setting of the switch 32 is generated.
It is input as EF to the reference input 22 of the digital-to-analog converter 14.

Therefore, the circuit consisting of the voltage dividing layer 24, the digital-to-analog converter 26 and the digital code switch 32 is, in principle, a variable voltage source reference voltage setting consisting of a DC power supply 50 and a variable resistor 52, as shown in FIG. It constitutes a circuit. The reference voltage VREF is output from the movable terminal 22 of the variable resistor 52. Note that the voltage divider 2 shown in FIG.
4. Instead of the digital/analog conversion 'jA2B and the digital code switch 32, a variable voltage source reference voltage setting circuit consisting of such a DC power supply 50 and variable resistor 52 is used as the reference input 2 of the analog/digital converter 14.
It may be connected to 2.

Digital/analog conversion: R14 outputs an analog signal with a level corresponding to the digital data of input 12! 8
occurs in The changing range between the maximum value and the minimum value of the output analog voltage depends on the reference voltage VREF. This means that the contrast of the video signal at the input 12 is controlled by the reference voltage VREF.

Therefore, in this device, CI'l? The contrast of one image displayed on the display screen 40 of 3B can be adjusted by operating the digital code switch 32.

The analog output 18 of the digital-to-analog converter 14 is connected through an output amplifier 34 to the cathode input 38 of the CRT 3B.

The CRT O8 is a high-brightness black-and-white cathode ray tube, and a lens optical system 42 is disposed in front of the display screen 40 so that the displayed image on the screen 40 is transferred to -L of the image recording medium 44.
It is configured so that the image is formed on the Furthermore, CRT 38
Since other circuit elements such as the deflection circuit are not directly related to the understanding of the present invention, illustration thereof is omitted to avoid complicating the figure.

A color filter 46 is disposed behind the lens optical system 42. This is three filters of three primary colors, and a drive mechanism (not shown) selectively selects one of them to control the light of the lens optical system 42. inserted into the shaft.

In this embodiment, the image recording medium 44 is a photosensitive material such as a roll of color photographic paper, and is fed one frame at a time by a drive mechanism (not shown) to complete recording of one frame of image. These constitute an image recording section that creates a hard copy of the image represented by the video signal.

Reading of the video signal from the frame memory 10 is controlled by a readout control section 16. The read control section 16 has a reference oscillation function for generating a stable reference clock, and its control line 48 is connected to the frame memory 10. Frame memory 10 read clock 1 read enable,
A control signal such as a read address is sent to the control line 48, and a driving clock CLK of the digital-to-analog converter 14 is sent to the control line 48.
are output to the control line 20, respectively.

The frame memory 10 stores, for example, a video signal for one field or one frame read out from a video floppy and converted into a digital signal. The write control is controlled by a write controller (not shown) of the device.

The 12 image signals of one frame or one field stored in the frame memory 10 are read out to an output 18 for each separated color under the control of a section 16 that controls one readout, for example, in a TV signal relation. For example, when a red (R) video signal is read out, it is converted into a corresponding analog signal by the digital-to-analog converter 14, amplified by the amplifier 34,
Input to CRT 3B. When converted into an analog signal, an analog signal level is given with a contrast according to the reference voltage νREF set to the reference input 22 by the digital code switch 32.

For example, as shown in the example of the luminance signal waveform in FIG. 3, when a high value is set with the digital code switch 32, a high-contrast analog video signal as shown by the song &180 is output to the output 18 of the digital-to-analog converter 14. output, and when you set a lower value.

An analog video signal with low contrast as shown by a curve 62 is output.

When displaying a red image on the CRT 3G, the red filter of the color filters 4B is inserted into the optical axis of the lens optical system 42. In this way, the predetermined image of Akama Uta is displayed on the CRT 38.
The recording medium 44 is exposed by displaying and outputting it on the display screen 40 of. As a result, the red image is transferred to the recording medium 44.
recorded in one frame.

Similarly, the readout control unit 16 controls green (G) and blue CB.
) are sequentially read out from the frame memo IJIO, and correspondingly, by selectively inserting green and blue filters in front of the lens optical system 42, a separated color image of the same frame is read out from the same image on the recording medium 44. Record over the frames using the additive color method. By later developing and fixing the recording medium 44, a hard copy of the color image can be obtained.

As described above, in this embodiment, the contrast of the image output to the display screen 40 of the CRT 3G is adjusted by adjusting the level VREF of the reference input 22 of the digital-to-analog converter 14 that converts a digital video signal into an analog signal. can be adjusted. Since this contrast adjustment is performed on the digital signal, high stability can be obtained. In particular, when the digital code switch 32 is used, it is less susceptible to the drift of a single circuit element, and more stable contrast adjustment can be achieved at a lower cost.

Effects As described above, in the present invention, the contrast of the image displayed on the CRT is adjusted by adjusting the reference input level of the digital-to-analog conversion circuit for the digital image signal. Therefore, contrast adjustment can be performed with high stability. This is particularly effective in the case of an image recording device that creates a hard copy of an image from a video signal, since it can provide a high quality image.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing an embodiment in which the last month is applied to an image recording device that creates a hard copy of an image from a video signal, and Fig. 2 shows reference voltage generation in the embodiment shown in Fig. 1. The circuit diagram showing the principle structure of the part. FIG. 3 is a waveform diagram showing an example of a video signal waveform for explaining contrast adjustment in the same embodiment. Explanation of symbols of main parts 10, . . . Frame memory 14. 26. , digital-to-analog converter 18, .
, readout control unit 22, , reference input terminal 32, , digital code switch 36, , CRT Patent applicant: Fuji Photo Film Co., Ltd. Representative: Takao Katori Takao Maruyama

Claims (1)

[Claims] 1. Signal conversion means to which a digital video signal is input and converts the video signal into a corresponding analog signal within a level range corresponding to a reference input; and an output of the signal conversion means. cathode ray tube means for receiving an analog signal and visually displaying an image represented by the analog signal; and reference input means for adjustablely generating the reference input and providing the reference input to the signal converting means; A contrast adjustment device for a CRT, characterized in that the contrast of an image represented by the analog signal is adjusted by adjusting an input means. 2. In the device according to claim 1, the reference input means includes: variable resistance means for manually setting the reference input; and a DC voltage source connected to the variable resistance means. A contrast adjustment device comprising: an output of the variable resistance means is applied to the signal conversion means as the reference input. 3. The apparatus according to claim 1, wherein the reference input means comprises: a coding switch means for manually setting the value of the reference input and generating a code representing the set value; and a coding switch means connected to the output of the coding switch means for converting the code into a corresponding analog signal. and a second signal converting means for providing the reference input to the signal converting means. 4. The apparatus according to claim 1, further comprising recording means for forming an image displayed by the cathode ray tube means onto a photosensitive material and recording the image on the photosensitive material. Features a contrast adjustment device.