JPH03293879A - Image memory device - Google Patents

Abstract

PURPOSE:To enable this device to be also used for an image printer by performing noise reduction in a moment when a video signal is fetched in image memory. CONSTITUTION:An inputted video signal is A/D-converted, and written on the image memory 4 after being added on output from a data conversion part 12. The noise reduction is performed by writing data on the image memory 4 when a memory signal is supplied from a control part 11, reading out the image data of one picture before in the image memory 4, performing the subtraction between A/D conversion output by a subtracter 3, discriminating whether or not it is a noise, and supplying data conversion output to an adder 2. In such a manner, it is possible to hold a still picture like the image printer, and to obtain a memory device most optimum for the various kinds of video equipment to print the data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image memory device used in video tape recorders, image printers, and the like.

(Prior Art) In recent years, video equipment such as television receivers and video tape recorders have become more multi-functional and have higher image quality, and image printers that faithfully make hard copies of images are attracting attention. Because it takes a long time to print, an image memory that temporarily stores the image to be printed is essential.However, the image memory device used in conventional image printers usually stores video signals for one frame or one field. Reading is performed at a low speed according to writing and printing.Therefore, when a video tape recorder, which is widely used for home use, is used as an image source, even if there is noise in the playback signal, the image memory is stored as is. is stored in
It had the disadvantage that it would be printed.

On the other hand, a device using an image memory device has been proposed in order to reduce screen noise in a video table recorder. FIG. 4 is a block diagram showing an example of an image memory device used in such a conventional video tape recorder. In this figure, the image signal given to the input terminal is A/
In the D-conversion converter method, the signal is converted into a digital signal and added to the adder 2.
and is given to the subtractor 3. The output of adder 2 is given to image memory 4. The image memory 4 is, for example, a memory device having a capacity for one frame or one field, and
Stores image data for fields or l frames, 1
The stored signals are controlled to be read out in synchronization with a delay of one field or one frame. The output of the image memory 4 is then given to a subtracter 3 and a changeover switch 5. The subtracter 3 subtracts the output of the A/D converter 1 from the signal read out from the image memory 4, thereby calculating the signal difference at the same position that differs by one field or one frame, and provides it to the data converter 6. There is. The data conversion section 6 performs data conversion by multiplying the output of the subtracter 3 by a feedback coefficient determined according to the applied subtraction output. If the output of the subtracter is below a predetermined level, the difference in this feedback coefficient is considered to be noise, so data conversion is performed based on this difference, and adder 2 adds it to the output of A/D converter 1. This reduces noise at that location.

The addition output of the adder 2 is sent to the image memory 4 and the changeover switch 5.
give to When playing a normal still image, the changeover switch 5 outputs the A/D converted output directly to the adder 2.
The output from the image memory 2 is read out via the changeover switch 5. The output is then converted into an analog signal by a D/A converter 7 and output as a video output. When the noise reduction function is installed, the image memory 4 is in a state where signals given with a time difference of one field or one frame are sequentially written and read, and the subtracter 3 performs subtraction as described above. Then, it is determined whether it is noise or a signal based on the subtracted output, and the signal difference is multiplied by a feedback coefficient determined based on the determination to obtain a data conversion output, and the adder 2
to cancel out the noise component. Then, the addition output is converted into an analog signal by a D/A converter 7 via a changeover switch 5 and output.

[Problems to be Solved by the Invention] However, in such conventional image memory devices, when the noise reduction function is activated, the image memory is constantly in a writing/reading state, and the images written in the image memory disappear one after another. become. Therefore, the method of using the image memory normally used in image printers is to write an appropriate image into the image memory once, search for other good moments, and as a result, if there is another suitable image, There is a drawback that the image memory cannot be used to print images that have already been stored in the image memory unless there is another suitable screen after rewriting the image memory.

The present invention has been made in view of the problems of the conventional image memory device, and has an object to perform a noise reduction function at the moment when a video signal is taken into the image memory, and to enable the device to be used in an image printer. is a technical issue.

Means for Solving Problem C] The invention of claim 1 of the present application includes an A/D converter that A/D converts a given image signal, and an A/D converter that stores at least one screen of video signals, and stores the image of one screen before. an image memory for reading data;
A/D from the digital video signal read from the image memory
It has a subtracter that subtracts the output of the converter and a writing number counting means that counts the number of writings per screen, and controls writing and reading of images to and from the image memory until a predetermined number of writings is reached. It is characterized by comprising a control section, a data conversion section that performs data conversion of the output of the subtracter, and a charger that adds the output of the data conversion section and the output of the A/D converter and writes it into the image memory. That is.

Further, in the invention according to claim 2 of the present application, the control section has feedback characteristic selection means for selecting the feedback characteristic based on the count value of the write number counting means, and the data conversion section has feedback characteristic selection means for selecting the feedback characteristic based on the count value of the write number counting means. The present invention is characterized in that the subtracted output data is converted based on the feedback characteristic.

Furthermore, the invention according to claim 3 of the present application is characterized in that the feedback characteristic selection means selects a feedback characteristic whose feedback coefficient increases as the number of writes increases.

[Effect]

According to the present invention having such features, the input video signal is A/D converted, and written into the image memory by adding it to the output from the data conversion section. Then, when a storage signal from the control unit is given, data is written to the image memory, the image data of one screen before the image memory is read out, and the subtractor performs subtraction with the A/D conversion output, and based on the subtracted value, Noise reduction is performed by determining whether it is noise or not and providing a data conversion output to an adder.

〔Example〕

FIG. 1 is a block diagram showing the configuration of an image memory device according to an embodiment of the present invention. In this figure, the same parts as those in the conventional example described above are given the same reference numerals, and detailed explanation will be omitted.

In this embodiment as well, the input signal is applied to the A/D converter 1, converted into a digital signal, and applied to the adder 2 and subtracter 3.

The output of adder 2 is given to image memory 4 and changeover switch 5. The image memory 4 continuously writes, reads, or stops writing in accordance with a control signal given from the outside, and the read signal is given to the subtractor 3 and changeover switch 5, as described above. Similar to the example. In this embodiment, an operation section 10 is provided for setting noise reduction on/off and writing information to the image memory, and its output is sent to a control section 11.
given to. The control unit 11 includes, for example, a microcomputer, a memory that defines its operation, and an input/output interface, and includes a mode selection unit 11a that selects a normal still image holding mode and a noise reduction mode, and a write mode that counts the number of writes. Number counting means 11b and feedback characteristic selection means 11c for selecting a feedback characteristic based on the number of times of writing.
This function has been achieved. A write control signal from the control section 11 is given to the image memory 4, and a selection output of the feedback characteristic is given to the data conversion section 12. The data conversion section 12 multiplies the subtraction output by a predetermined coefficient based on the subtraction output from the subtracter 3 and the output from the feedback characteristic selection means 11c based on the given feedback characteristic, and supplies the result to the adder 2. In order to select the output corresponding to the subtracted output from the subtracter 3, the data converter 12 may use a ROM whose input/output characteristics are defined in advance and switch the ROM in response to a feedback characteristic selection signal. Alternatively, it may be configured by a count determination section that determines the count based on the subtraction output, and a multiplier that multiplies the count by the subtraction output. The output of the changeover switch 5 is connected to a D/A converter 7 and a thermal head 13 of an image printer.

Next, the operation of this embodiment will be explained. When a still image is to be reproduced or printed without using the noise reduction function, a still image selection mode is given to the control section 11 from the operation section 10. Then, a write signal is given to the image memory 4 via the mode selection means 11a, and the A/D converter 1
The D-converted signal applied via the adder 2 is written into the image memory 4 as it is. The retained image data is then sequentially read out from the image memory 4 and output to the D/A converter 7 and the thermal head 13 via the changeover switch 5 to reproduce a still image. In this way, mode selection means 1
A still image at the time when the selection signal is applied from 1a can be taken into the image memory 4 and reproduced.

Now, when the noise reduction function is turned on by the operation unit 10, the flowchart shown in FIG. 2 is executed, and the number of writes N is set to 1 in step 21. Then, the process advances to step 22 and waits for a memory command.

Now, when a memory command is input from the operation unit 10, the process proceeds from step 22 to step 23, and the vertical synchronization signal V 5yn is input.
Waiting for c. If vertical synchronization signal is given, step 2
In step 4, mode 1, that is, a signal that makes the feedback coefficient zero is applied to the data converter 12. Since the data converter 12 selects a ROM whose coefficient is zero, all signals output from the data converter 12 for one field are zero.

Therefore, the output of one field is directly given to the image memory 4 by the adder 2, and is overwritten and recorded in the image memory 4. In the control unit 11, step 25
．． Proceeding to step 26, it is checked whether the mode is noise reduction mode (NR mode) and whether the number of writes N has reached 5.

If it is less than or equal to 5, the process advances to step 27 to increment the number of writes N, and returns to step 23 to wait for a vertical synchronizing signal.

Now, if the next vertical synchronizing signal is given, the process proceeds to step 24, where the mode 2 selection output is given from the control section 11 to the data conversion section 12. Here, the feedback characteristic of mode 2 is, for example,
As shown in the figure, the output from subtracter 3 is between -64 and +64.
The output is changed as shown in the figure. and ±32
In this case, the feedback coefficient is set to 2 when the output is in the range of ±16, that is, from -32 to +32, and the feedback coefficient is gradually lowered in the range up to ±64. In addition, since it is determined that the image data itself between fields is different between +64 and above and -64 and below,
The feedback characteristic is set to zero, and the output of the data converter 12 is set to zero.

In this way, the adder 2 adds the output of the data converter 12 and the A/D conversion output, and writes the result into the image memory 4. Then, in steps 25, 26, and 27, a similar check is performed, N is incremented, and the process returns to step 23. Then, in the third frame, the output of mode 3, that is, the ROM of the data converter 12 having the characteristic that the feedback coefficient is directly expanded as shown in FIG. In this way, the characteristics of the data converter 12 are changed so that each field has a different feedback characteristic. Then, for example, the converted data for four fields is written into the image memory 4, and the operation is stopped.

In this way, the noise-reduced image data for four fields can be held in the image memory 4 after the memory switch of the operation unit 10 is pressed, and the changeover switch 5 is then switched to the image memory 4 bias. This allows the data held in the image memory 4 to be output. Here, the control unit 11 performs steps 23.25 to 27.
In step 24, the function of the writing number counting means 11b which counts the number of writings per screen is achieved, and in step 24, the function of the feedback characteristic selection means 11c which selects the feedback characteristic corresponding to the number of writings is achieved. ing.

By increasing the feedback characteristic coefficients as shown in Figure 3, the weighting does not change exponentially for each field, and a large noise reduction effect can be achieved with a small number of writes. . Further, by arbitrarily changing this feedback characteristic for each field, it is also possible to obtain noise reduction effects with various characteristics.

In this embodiment, in order to perform noise reduction, image data for four fields is converted and written to the image memory, but this means that the four fields are substantially the same image. If different images are obtained, they will be treated as different data due to the feedback characteristics shown in FIG. 3, and it goes without saying that the noise reduction effect will not be obtained. Moreover, it goes without saying that the data conversion is not limited to the data conversion of images for four fields, and any number of fields or frames can be selected.

〔Effect of the invention〕

As described in detail above, according to the present invention, since noise reduction is performed when a video signal is held in an image memory, a noise-free image can be held in the image memory. Further, when selecting another screen, the image can be similarly retained in the image memory when it is imported into the image memory by a storage operation from the operation section.

Therefore, the image memory device is ideal for various video devices such as image printers that hold still images and print the data.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an image memory device according to an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the control section of this embodiment, and FIG. 3 shows the input/output characteristics of the data conversion section. 4 are block diagrams showing the configuration of a conventional image memory device. 1--A/D converter 2 Subtractor 4--Image memo 10--Operation section 11 a-=--Mode selection means number counting means 11c/12・−・・−・Data conversion section. Adder 3 - - - Switching switch 11 - - Control section i i b - - Write cycle feedback characteristic selection means Fig. - - hoN removal 1 11------1 size & part 3------1 sq.

Claims (3)

[Claims] (1) An A/D converter that A/D converts a given image signal; an image memory that stores at least one screen of video signals and reads out image data of the previous screen; a subtracter that subtracts the output of the A/D converter from the digital video signal, and a writing number counting means that counts the number of writings per screen, and the image memory a control unit that controls writing and reading of images to and from the image; a data conversion unit that converts the output of the subtracter; and an output of the data conversion unit and the A/D converter to add the output of the data conversion unit and the output of the A/D converter to generate the image. An image memory device comprising: an adder for writing to memory. (2) The control section has a feedback characteristic selection means for selecting a feedback characteristic based on the count value of the write number counting means, and the data conversion section has a feedback characteristic selected by the feedback characteristic selection means of the control section. 2. The image memory device according to claim 1, wherein the image memory device converts the subtracted output data based on . (3) The image memory device according to claim 2, wherein the feedback characteristic selection means selects a feedback characteristic whose feedback coefficient increases as the number of writes increases.