JPH03224377A - Picture display device - Google Patents

Abstract

PURPOSE:To eliminate the need for A/D conversion because a signal extracted externally is a digital signal by providing a terminal to extract externally a digital picture signal outputted sequentially from a frame memory together with a synchronizing signal. CONSTITUTION:A clock signal outputted from a clock signal generating circuit 3a is inputted to a synchronizing signal generating circuit 3b forming a synchronizing signal generating circuit 3 together with the clock signal generating circuit 3a. The synchronizing signal generating circuit 3b based on the inputted clock signal generates a synchronizing signal required for the picture display device. Picture signals S1, S2 are outputted from a picture memory 1 and a character bit map memory 2 synchronously with the synchronizing signal to a lookup table 5 as parallel digital signals so that the picture signal S1 outputted from the picture memory 1 forms a low-order bit and the picture signal S2 outputted from the character bit map memory 2 forms a high-order bit.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is an image display method in which a digital image signal is stored in a frame memory, the digital image signal is read out, converted into a video signal, and displayed on a display screen. It is related to the device.

(Prior Art) Image display devices such as CRT display devices and liquid crystal display devices that display various images on a display screen are widely used.

These image display devices usually store digital image signals for one screen in a frame memory, read out each pixel that makes up the screen in order, perform D/A conversion, and generate a video signal. The device is configured to display a visible image on the display screen by scanning the display screen with an electron beam in the case of a CRT display device, for example, based on a video signal. In addition, it is widely used to display characters, etc. superimposed on the visible image, and in this case, in order to be able to freely change the position of the characters on the display screen, the above-mentioned method is used. In addition to the frame memory, there is another frame memory for storing characters, etc. as image signals, and the images stored in these two frame memories are generally displayed in a superimposed form on the display screen. It is.

In recent years, technology for displaying finer images with higher precision (hereinafter referred to as "high-definition images") without flickering in image display devices such as those described above has also progressed. One of the techniques for displaying higher-definition images on a display screen is to increase the number of pixels per scanning line, and to increase the number of scans per screen. There is a method of increasing the scanning speed in order to display images without flickering, and this trend has been gaining momentum in recent years.

- For example: - Number of pixels per scan line is approximately 1000
The number of scans per screen is about 1,000, and the entire display screen is scanned about 70 times per second. In this case, the time per pixel for display is L
Onsec, or less, and is extremely fast.

On the other hand, there are many requests to obtain a hard copy of the visible image as needed while observing the visible image displayed on the display screen of the image display device as described above using a laser printer device or the like. Technologies for this purpose have also been developed. One method is to take the video signal outside the image display device, convert it into an A/D converter, and obtain a hard copy using a laser printer or the like.

Another method is to take out the signal transferred from the image storage device and before it is written to the frame memory as an image signal and store it in another memory, and based on the signal stored in this memory, There is a method of obtaining a hard copy using a laser printer or the like.

(Problem to be Solved by the Invention) When obtaining a hard copy of an image displayed on the display screen of an image display device configured to display a high-definition image without flickering, the image display device Various problems arise due to the very high speed and lock-based operation.

For example, if you take the video signal outside and perform A/D conversion to obtain a hard copy using a laser printer, etc., you will need a very high-speed A/D converter. There are few A/D converters that are sufficient to A/D convert a video signal, and even if there are, they are very expensive.

In order to solve the above problems, in addition to displaying a high-definition image without flickering on the display screen of an image display device, we also created a video signal from this signal that has coarser pixels and a reduced number of scans so that it is compatible with ordinary televisions, etc. 2. Description of the Related Art Image display devices are known that are configured to generate a signal and output the video signal to the outside. However, the video signal output from this image display device no longer carries a high-definition image, and the problem is that the hard copy obtained based on this video signal has degraded image quality. be.

In addition, for example, a method of extracting a signal transferred from an image storage device before being written to the frame memory, storing it in another memory, and obtaining a hard copy based on the signal stored in this memory is as follows. Since signals can be read out from the memory at a sufficiently slow speed, it is advantageous in that a slow and inexpensive laser printer or the like can be used. However, when superimposing an image and text on a display screen, for example, the text information transferred from an image storage device, etc. is encoded in ASCII code, etc., and this text information is Normally, the position of the character on the display screen is determined when writing to the frame memory.

Therefore, if the signal is extracted externally before being written to the frame memory, it becomes necessary to determine the font and position of the characters on the hard copy separately from those displayed on the display screen of the image display device. However, there is a problem in that the font and position of the font may be different from what is displayed on the display screen.

The present invention has been made in view of the various problems mentioned above, and even in an image display device that performs high-speed processing such as displaying high-definition images without flickering, it is necessary to perform high-speed A/D conversion externally. To provide an image display device having a configuration that is compatible with an image display device configured to store image signals and characters such as characters in separate frame memories and display these signals without the need for an image display device. The purpose is to

(Means for Solving the Problems) A first image display device of the present invention includes a frame memory for storing digital image signals, and a sequential D/A converter for sequentially outputting the digital image signals pixel by pixel from the frame memory. a D/A converter that converts and outputs a video signal; a display unit that displays a visible image based on the video signal; a timing for sequentially outputting the digital image signal from the frame memory; and a timing for the D/A conversion; It is characterized by comprising a synchronization signal generation unit that outputs a synchronization signal for synchronizing with the timing of the display, and a terminal for taking out the digital image signals sequentially output from the frame memory together with the synchronization signal. That is.

Further, a second image display device of the present invention includes a frame memory for storing digital image signals, and outputs a video signal by sequentially D/A converting the digital image signals sequentially output pixel by pixel from the frame memory. a D/A converter for displaying a visible image based on the video signal; synchronization between the timing of sequentially outputting the digital image signal from the frame memory, the timing of the D/A conversion, and the timing of the display; a synchronization signal generation unit that switches and outputs a first synchronization signal for the display and a second synchronization signal having a lower clock frequency than the first synchronization signal, and sequentially outputs from the frame memory. The present invention is characterized in that it includes a terminal for taking out the digital image signal obtained along with the second synchronization signal to the outside.

Further, a third image display device of the present invention includes a frame memory for storing digital image signals, and outputs a video signal by sequentially D/A converting the digital image signals sequentially output pixel by pixel from the frame memory. a D/A converter for displaying a visible image based on the video signal; synchronization between the timing of sequentially outputting the digital image signal from the frame memory, the timing of the D/A conversion, and the timing of the display; a synchronization signal generation unit that switches and outputs a first synchronization signal for the display and a second synchronization signal having a lower clock frequency than the first synchronization signal; and the D/A converter. The present invention is characterized in that it includes a terminal for taking out the video signal outputted from the apparatus together with the second synchronizing signal to the outside.

Here, the method of "extracting the video signal to the outside together with the second synchronization signal" in the third image display device is not limited to a particular method; for example, the method of "extracting the video signal to the outside together with the second synchronization signal" The signals may be extracted in parallel, or these signals may be extracted as a composite video signal.

(Function) The above-mentioned first image display device of the present invention is equipped with a terminal for taking out to the outside the digital image signals sequentially outputted from the frame memory together with the synchronization signal, so that the signals taken out to the outside are the digital signals. Therefore, A/D conversion is not necessary, and therefore it is suitable for image display devices that perform high-speed processing. Moreover, since the signal is output from the frame memory, it is a signal that has already been bit mapped, and the font and position of the characters on the screen are the same as the image displayed on the display screen.

However, when the above-mentioned first image display device extracts a signal from an image display device that performs very high-speed processing, the first image display device performs correspondingly very high-speed processing because the signal is a very high-speed signal. It is necessary to prepare an expensive laser printer or the like that can be used, and the wiring from the image display device to the laser printer or the like must be kept as short as possible.

The second image display device of the present invention not only has the same effects as the first image display device, but also eliminates the limitations of the first image display device. That is, in the second image display device of the present invention, the synchronization signal generation section generates a first synchronization signal for displaying a visible image on the display section and a second synchronization signal having a lower clock frequency than the first synchronization signal. Since the second synchronization signal is switched and output, normally the first synchronization signal is output and a visible image is displayed on the display.
By using the second synchronization signal only at the moment when the signal is taken out to the outside, the display on the display unit may be hindered at the moment when the signal is taken out to the outside, but it has almost no effect on the observation of visible images, and Since the signal extracted at the time is relatively low-speed, it is sufficient to prepare a relatively low-speed, relatively inexpensive laser printer, etc., and even if the distance between the image display device and the laser printer, etc. is relatively large, good.

Further, the third image display device of the present invention, which extracts a video signal, is equipped with a synchronization signal generation section having the same configuration as the second image display device, so it can output a relatively low-speed video signal. can be taken out to the outside, therefore, a relatively low-speed A/D converter is sufficient for external A/D conversion, and a relatively low-speed and relatively inexpensive laser printer device or the like may be prepared.

Furthermore, the signals output from the first to third image display devices carry the same visible image displayed on the display unit, for example, a high-definition image, and are the same as the visible image displayed on the display unit. You can get a hard copy with level image quality.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an image display device of the present invention.

This image display device displays high-definition images without flickering, and has a large number of pixels per scanning line (for example, 1500 pixels) and a large number of scanning lines (for example, 1000 pixels).
books) and high-speed scanning (e.g. 70 screens/sec)
It is structured as follows.

In the image memory 1, a digital image signal is manually inputted from the outside and stored in a bit mapped format.

Further, the character bitmap memory 2 also stores information such as characters in a bitmapped format. Further, the clock signal generation circuit 3a constituting the synchronization signal generation circuit 3 uses a clock signal a, which is the basis for obtaining a synchronization signal at a speed suitable for displaying an image on the CRT display 4, and an external clock signal a, for example, not shown. This is the basis for finding a speed synchronization signal suitable for laser printer equipment.
The switching means 3a generates both a second clock signal having a lower clock frequency than the clock signal and switches them.
The clock signals a and b are switched so that only one of the clock signals a and b is output at a time.

The clock signal output from this clock signal generation circuit 3a is input to a synchronization signal generation circuit 3b which constitutes a synchronization signal generation circuit 3 together with this clock signal generation circuit 3a. The synchronization signal generation circuit 3b generates a synchronization signal necessary for this image display device based on the input clock signal. Note that synchronization signals with different timing or waveforms may be required for each block shown in the figure, but these are collectively referred to as synchronization signals here.

Image signals S1 and S2 are outputted from the image memory 1 and the character bitmap memory 2 in synchronization with this synchronization signal, and the image signal S1 outputted from the image memory 1 constitutes the lower bit, and the character bitmap memory 2 The image signal S2 outputted from the lookup table 5 is input as a parallel digital signal so as to constitute the upper bits. The lookup table 5 converts the input signals (image signals S1 and 82) as described above and outputs a digital image signal S3 corresponding to the image actually displayed on the CRT display.

FIG. 2 shows the input signal Sl to the lookup table 5,
FIG. 3 is a graph of a conversion table for converting S2 into an output signal S3.

Lookup table 5 output from image memory 1
Image signal S1 constituting the lower bits of the input signal of
As the value of , the output signal S3 also increases, but when the image signal S2 representing a character is output from the character bitmap memory 2, the second
The value is to the right of point A shown in the figure, and is displayed in white on the CRT display 4. That is, an image with white characters superimposed on the image is displayed on the CRT display 4 based on the image signal S1 stored in the image memory 1.

Digital image signal S3 output from lookup table 5 is input to D/A converter 6 to generate video signal S4. This video signal S4 is input to the CRT display 4, and a visible image based on the input video signal S4 is displayed on the CRT display 4.

Here, the digital image signal S3 and the synchronization signal are connected to a terminal 7 for taking out the signals to the outside of this image display device. Switching means 3 of clock signal generation circuit 3a
C normally switches the signal path to output a clock signal a with a high clock frequency suitable for displaying image quality on the CRT display 4, and when taking out the signal from the terminal 7, outputs a clock signal a with a low clock frequency. The signal path is switched so that the clock signal a is outputted, and when the signal for one screen has been outputted, the signal path is switched again so that the clock signal a is outputted. Here, the synchronization signal outputted via the terminal 7 reproduces an image based on the digital image signal S3, which is output externally away from this image display device and is synchronized with the synchronization signal used inside this image display device. The digital image signal S3 and the synchronization signal outputted to the outside are input to, for example, a laser printer device, and a hard copy of the image represented by the digital image signal S3 is obtained. Digital image signal S output externally
3 carries a high-definition image, so C
A hard copy of the image can be obtained with the same resolution as the visible image displayed on the RT display 4.

Here, the terminal 7 outputs the digital image signal S3.
Instead of providing a terminal 7' for outputting the video signal S4 together with a synchronizing signal, the video signal S4 may be A/D converted as required after being output from the image display device. When outputting the video signal S4, the slow clock b is used as in the above embodiment.

Furthermore, depending on the processing speed inside this image display device, the purpose of the signal output from this image display device, and the performance of an externally prepared device such as a laser printer, the clock signal generation circuit 3a always outputs a CRT display. The digital signal S3 may be configured to be output from the terminal 8 together with a synchronization signal generated using this clock signal. Even with this configuration, it is possible to extract an image signal carrying the same image as the visible image displayed on the CRT display 4, including the font of the characters and their arrangement positions. , and high-speed A/D
This has the advantage that there is no need to prepare a converter.

FIG. 3 is a block diagram showing another embodiment of the image display device of the present invention. Blocks having the same functions as each block of the image display device shown in FIG. 1 are given the same numbers as those shown in FIG. 1, and the explanation thereof will be omitted.

The clock signal generation circuit 3a' constituting the synchronization signal generation circuit 3' in this embodiment is the same as the signal generation circuit 3 in the embodiment described above, which switches and outputs two types of clock signals having different clock frequencies. Instead, only one type of clock signal is generated and outputted to the synchronization signal generation circuit 3b', and in this embodiment, the function of generating two types of synchronization signals with different clock frequencies is the synchronization signal generation function. The circuit 3b' is in charge of this. That is, a programmable counter or the like is used as the synchronization signal generation circuit 3b', and a switching signal S5 for switching the synchronization speed is input together with the clock signal output from the clock signal generation circuit 3a'. Based on this, a high-speed first synchronization signal suitable for displaying an image on a CRT display or a relatively low-speed second synchronization signal suitable for taking out the signal to the outside is generated and output. In this way, the means for generating the first and second synchronization signals is not limited to a specific means.

Furthermore, although the embodiment shown in FIG. 3 is an example in which the video signal S4 is taken out together with the synchronizing signal, these two signals are not taken out in parallel. That is, a signal synthesis circuit 8 is provided which inputs the video signal S4 and the synchronization signal and generates a composite video signal S4' in which these signals are synthesized.
4' is output from terminal 7'. In this way, the output method of the video signal and synchronization signal is not limited to any particular method.

(Effects of the Invention) As described above in detail, the first image display device of the present invention is capable of extracting the digital image signals sequentially output from the frame memory together with the synchronization signal, and therefore the A/D conversion is not necessary and is suitable for image display devices that perform high-speed processing. Furthermore, the image signal carrying the image itself displayed on the display screen, including the font of characters and the placement position of the display screen, can be extracted to the outside. .

In addition, the second image display device of the present invention uses a second synchronization signal with a lower clock frequency when extracting the digital image signal to the outside, so in addition to the effects of the first image display device, For example, it is sufficient to prepare a relatively low-speed laser printer, and it is easy to arrange the laser printer or the like at a relatively distant position from the second image display device.

Furthermore, the third image display device of the present invention is similar to the conventional technology in that it takes out the video signal to the outside, but
Similar to the second image display device, the second synchronization signal with a lower clock frequency is used when taking out the video signal to the outside, so even when an external A/D converter is provided, it is relatively A relatively inexpensive A/D converter with low response may be provided. Furthermore, it is possible to extract a video signal carrying the same image as the visible image displayed on the display screen, including the fonts and layout positions of characters and image resolution.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the image display device of the present invention, FIG. 2 is a graph showing a conversion table in the lookup table shown in FIG. 1, and FIG. FIG. 2 is a block diagram showing another embodiment of the image display device of the present invention. 1... Image memory 2... Character bitmap memory 3... Synchronous signal generation circuit 3a... Clock signal generation circuit 3b... Synchronization signal generation circuit 4... CRT display 5... Look Up table 6...D/A converter 7.7'7'...Terminal 8...Signal synthesis circuit S3...Digital image signal S4...Video signal

Claims (3)

[Claims] (1) A frame memory for storing digital image signals, a D/A converter that sequentially D/A converts the digital image signals sequentially output pixel by pixel from the frame memory and outputs a video signal, and the video signal. a display unit that displays a visible image based on the frame memory; a synchronizer that outputs a synchronization signal for synchronizing the timing of sequentially outputting the digital image signals from the frame memory, the timing of the D/A conversion, and the timing of the display; An image display device comprising: a signal generating section; and a terminal for extracting digital image signals sequentially output from the frame memory together with the synchronization signal. (2) a frame memory for storing digital image signals; a D/A converter that sequentially D/A converts the digital image signals sequentially output pixel by pixel from the frame memory to output a video signal; and the video signal. a display unit that displays a visible image based on the display unit; and a second synchronization signal having a lower clock frequency than the first synchronization signal. An image display device characterized by comprising a terminal for outputting a synchronizing signal to the outside. (3) a frame memory for storing digital image signals; a D/A converter that sequentially D/A converts the digital image signals sequentially output pixel by pixel from the frame memory to output a video signal; and the video signal. a display unit that displays a visible image based on the frame memory, a first display unit for synchronizing the timing of sequentially outputting the digital image signals from the frame memory, the timing of the D/A conversion, and the timing of the display and a second synchronization signal having a lower clock frequency than the first synchronization signal. An image display device characterized by comprising a terminal for outputting a synchronizing signal to the outside.