JPH06289828A - Image display device - Google Patents

Abstract

PURPOSE:To obtain the image display device which can prevent an image from deteriorating in quality owing to gradation compression by providing a gradation information compressing means and a noise pattern varying means. CONSTITUTION:The analog signal outputted from an image input device 1 is converted by an A/D converter 2 into a digital signal consisting of 8 bits each for R, G, and B, i.e., 24 bits in total. At this time, the number of bits of a frame memory 6 is 8, so the gradation information compressing means 14 compresses 24-bit full-color data to 8 bits and writes the result in the memory 6. Then the noise pattern varying means 15 varies a periodic noise pattern used for gradation information compression processing performed by the means 14 in synchronism with the vertical synchronizing signal of the device 1. Consequently, the value of a noise applied to pixels at the same positions of image data to be compressed is varied by frames or fields. Consequently, mean luminance is represented with specific area and luminance is also represented by time averaging, so the representing ability for the luminance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device capable of suppressing an increase in circuit scale and preventing deterioration of the quality of a gradation-compressed image.

[0002]

2. Description of the Related Art FIG. 12 is a block diagram showing a conventional image display apparatus of a picture-in-picture system.

This picture-in-picture type image display device is a display device capable of displaying a full-color image picked up by a video camera or the like on a computer screen which cannot be displayed in full-color.

In the figure, 1 is an image input device such as a video camera, and 2 is a full color video signal output from the image input device 1 (8 bits for each of RGB, a total of 24 bits).
A / D converter to convert to digital signal, 3 is 2
The 4-bit full color frame memory 4 is a D / A converter for converting the output of the 24-bit full color frame memory 3 into an analog signal.

A computer 5 is provided with a CPU 5a and a data storage device 5b. 6 is an 8-bit frame memory for computer screens managed by the CPU 5a,
Reference numeral 7 is a look-up table (hereinafter referred to as LUT) that outputs the 24-bit full color data stored at the corresponding address using the pixel value of the 8-bit frame memory 6 as an address, and 8 is a computer expanded to 24-bit full color data by the LUT 7. It is a D / A converter that converts screen data into an analog signal. Reference numeral 9 is an analog switch for switching between the two analog signals converted by the D / A converter 4 and the D / A converter 8, and 10 is a display device.

Next, the operation will be described. The image input by the image input device 1 is converted by the A / D converter 2 into a digital signal of a total of 24 bits of 8 bits for each of RGB and written in the 24-bit full color frame memory 3. Then, it is converted into an analog signal by the D / A converter 4 so as to match the sync signal of the display device 10. On the other hand, 8 managed by the CPU 5a
The data in the bit frame memory 6 is expanded to 24-bit full color data via the LUT 7 and then converted into an analog signal by the D / A converter 8 so as to match the sync signal of the display device 10.

The analog signal generated in this way is switched by the analog switch 9, and the image picked up by the video camera or the like is combined with the computer image and displayed on the display device 10.

[0008]

Since the conventional image display device is constructed as described above, it requires a 24-bit full color frame memory and two D / A converters, which is a circuit scale. There was a problem that became large. Further, since it is necessary to switch the analog switch 9 in accordance with the synchronization signal of the display device 10, there is a problem that a complicated circuit for controlling the switching timing of the analog switch is required.

The inventions of claims 1 to 3 provide an image display device capable of improving the image quality by improving the gradation expression capability during gradation compression and preventing deterioration of image quality due to gradation compression. The purpose is to

The inventions of claims 4 to 6 suppress the increase in circuit scale by performing gradation information compression processing on an image with a large number of gradation representations, and the gradation representation ability when gradation compression is performed. It is an object of the present invention to obtain an image display device capable of improving the image quality and the image quality.

According to the invention of claims 7 to 9, the gradation information compression processing is performed on the image supplied from the image input device so as to be displayed with the gradation number of the computer screen, and the increase of the circuit scale is suppressed. However, an object of the present invention is to obtain an image display device capable of improving the image quality by improving the tone expression capability when performing tone compression.

[0012]

In order to reduce the number of gradations, the image display device according to the invention of claim 1 superimposes periodic noise information having a periodic pattern on the image information stored in the frame memory. And a noise pattern changing means for changing the pattern of the periodic noise information every predetermined time, every frame period or every field period.

According to another aspect of the invention, there is provided the image display device, wherein the gradation information for cyclically changing the threshold value when the gradation information compression process for reducing the gradation number is performed on the image information stored in the frame memory. A compression means and a threshold pattern changing means for changing the cyclically changing threshold pattern every predetermined time, every frame cycle or every field cycle are provided.

An image display device according to a third aspect of the present invention is a gradation information compression means for performing gradation information compression processing for reducing the number of gradations in image information stored in a frame memory, and the gradation information compression thereof. Error diffusion means for adding the quantization error resulting from the gradation information compression processing by the means to the pixels of the rear frame or the rear field.

An image display device according to a fourth aspect of the present invention is an n-bit / pixel frame memory which can be directly drawn from a computer, and an N value (which is a subset of gradations capable of displaying the contents of the frame memory on a display). has a look-up table to expand the gradation of n ≦ 2 ^n), further image gradation information compression means and the periodic to reduce the number of gradations by superimposing a periodic noise information stored in the frame memory A noise pattern changing means for changing the pattern of noise information every predetermined time, every frame cycle or every field cycle, so that an image of M value (M> N) can be displayed in the gradation of N value. This is converted into n bits and drawn in the frame memory.

The image display device according to a fifth aspect of the present invention is gradation information compression for periodically changing a threshold value when performing gradation information compression processing for reducing the number of gradation levels of an image drawn in a frame memory. Means and a threshold pattern changing means for changing the cyclically changing threshold pattern every predetermined time, every frame cycle or every field cycle, an image of M value (M> N) is gradation of N value. Is converted into n bits so that the data can be displayed by and is drawn in the frame memory.

According to the sixth aspect of the present invention, in the image display device, the quantization error resulting from the gradation information compression processing for reducing the number of gradations of the image drawn in the frame memory is temporally rearward frame or rearward field. The image of M value (M> N) is converted into n bits so that it can be displayed with the gradation of N value and is drawn in the frame memory by using the error diffusion means added to the pixel of is there.

According to a seventh aspect of the present invention, in an image display device, an image supplied from the image input device is displayed in m bits / pixel (m>
n), and the gradation information compression process for reducing the number of gradations by superimposing the periodic noise information having a periodic pattern on the digitized image, and the pattern of the periodic noise information. N is a subset of gradations that can be displayed on the display of the image digitized to m bits / pixel by changing the value of the image every predetermined time, every frame period or every field period.
The image data is converted into n bits so that it can be displayed with a gradation of a value (N ≦ 2 ⁿ ) and is drawn in the frame memory.

In the image display device according to an eighth aspect of the present invention, the threshold value for performing gradation information compression processing for reducing the number of gradations of the image drawn in the frame memory is periodically changed and The pattern of the threshold value that changes dynamically is changed every predetermined time, every frame period, or every field period, and the image supplied from the image input device and digitized into m bits is a subset of gradations that can be displayed on the display. Is converted into n bits so that the gradation can be displayed with N values (N ≦ 2 ⁿ ).

An image display device according to a ninth aspect of the present invention is an N value (N≤2) which is a subset of gradations capable of displaying an m-bit digitized image supplied from an image input device on a display. When converting to n bits so as to be displayed in ( ⁿ ) gradations, a quantization error resulting from the gradation information compression processing is added to pixels in a rear frame or a rear field.

[0021]

According to the image display device of the present invention, the periodic noise information having a periodic pattern is superimposed on the image information stored in the frame memory, and the periodic noise information pattern is formed at predetermined time intervals. Alternatively, it is possible to perform gradation information compression processing by changing the noise information added to the pixels at the same position by changing it for each frame cycle or field cycle, and to enable gradation expression by temporal averaging. (EN) It is possible to prevent deterioration of image quality due to gradation information compression processing for improving expression capability and image quality and suppressing an increase in device scale.

The image display device according to the invention of claim 2 is
When performing gradation information compression processing for reducing the number of gradations on the image information stored in the frame memory, not only is the threshold in the gradation information compression processing periodically changed,
By changing the threshold pattern of the above threshold value every predetermined time, every frame cycle, or every field cycle so that gradation can be expressed even by temporal averaging, the gradation expression capability is improved to improve the image quality. The deterioration of the image quality due to the gradation information compression processing for suppressing the increase in the device scale is prevented.

The image display device according to the invention of claim 3 is
When performing the gradation information compression processing to reduce the number of gradations on the image information stored in the frame memory, the quantization error resulting from the gradation information compression processing is temporally transferred to pixels in the subsequent frame or the subsequent field. In addition, since the above quantization error is diffused in time, gradation expression can be performed even by temporal averaging, so that gradation expression capability is improved, image quality is improved, and device scale is increased. It is possible to prevent deterioration of image quality due to gradation information compression processing for suppressing.

The image display device according to the invention of claim 4 is
When converting an image of M value (M> N) into n bits so that it can be displayed by N value, periodic noise information having a periodic pattern is superimposed on the image of M value, and the periodic noise is generated. To improve the gradation expression capability by changing the information pattern every predetermined time, every frame cycle or every field cycle, and performing gradation information compression processing so that gradation can be expressed even by temporal averaging. Improves the image quality and suppresses the increase in the scale of the apparatus, while preventing the deterioration of the image quality due to the gradation compression.

The image display device according to the invention of claim 5 is
When converting an image with M values (M> N) to n bits so that it can be displayed with N values, not only is the threshold periodically changed, but the threshold pattern of the above threshold is set at predetermined time intervals or frame intervals. It is possible to improve the gradation expression capability and improve the image quality by suppressing the increase in the scale of the device while changing the gradation for each field period or field period so that the gradation expression can be performed by temporal averaging. Prevents deterioration of image quality due to tonal compression.

The image display device according to the invention of claim 6 is
When converting an image with M values (M> N) into n bits so that it can be displayed with N values, a quantization error resulting from the gradation information compression processing is temporally added to pixels in a rear frame or a rear field. By temporally diffusing the above-mentioned quantization error, the gradation expression ability by temporal averaging is improved and the image quality is improved, while suppressing an increase in device scale, while preventing deterioration of image quality due to gradation compression. .

An image display device according to a seventh aspect of the invention is
When gradation-compressing an image supplied from an image input device digitized to m bits / pixel (m> n) to n bits, the image information stored in the frame memory has a periodic pattern. While superimposing noise information, the pattern of the periodic noise information is changed every predetermined time, every frame cycle, or every field cycle,
By changing the noise information added to the pixels at the same position to perform gradation information compression processing and enabling gradation expression by temporal averaging, it is possible to improve the gradation expression capability and improve the image quality. The deterioration of image quality due to the gradation information compression processing for suppressing the increase in scale is prevented.

The image display device according to the invention of claim 8 is
When gradation-compressing an image supplied from an image input device digitized to m bits / pixel (m> n) to n bits, not only is the threshold in the gradation information compression process changed cyclically, By changing the threshold pattern of the above threshold value every predetermined time, every frame cycle, or every field cycle so that gradation can be expressed even by temporal averaging, the gradation expression capability is improved to improve the image quality. The deterioration of the image quality due to the gradation information compression processing for suppressing the increase in the device scale is prevented.

The image display device according to the invention of claim 9 is
When gradation-compressing an image supplied from an image input device digitized into m bits / pixel (m> n) to n bits, a quantization error resulting from the gradation information compression processing is temporally rearwardly framed. Alternatively, in addition to the pixels in the rear field, the above quantization error is diffused in time so that gradation can be expressed by a temporal average, so that the gradation expression capability is improved and the image quality is improved. The deterioration of the image quality due to the gradation information compression processing for suppressing the increase is prevented.

[0030]

【Example】

Embodiment 1 Hereinafter, an embodiment of the invention of claim 1 will be described with reference to the drawings. FIG. 1 is a block diagram showing the image display device of this embodiment.

In the figure, 1 is an image input device such as a video camera or a television tuner for receiving a television signal, and 2 is an analog signal (video signal) output from the image input device 1 in full color (a total of 8 bits for each RGB). Two
It is an A / D converter (A / D conversion means) for converting into a 4-bit digital signal. Reference numeral 5 denotes a computer, which includes a CPU 5a and a data storage device 5b. 1
Reference numeral 4 is a gradation information compression means for gradation-compressing the gradation information of the full-color digital signal output from the A / D converter 2, and 15 is a noise pattern used for gradation compression in the gradation information compression means 14. It is a noise pattern changing means for changing.

Reference numeral 16 is a digital switch for selecting which of the screen information supplied from the CPU 5a and the image by the image input device which has been gradation-compressed by the gradation information compression means to be written in the 8-bit frame memory 6. The digital switch 6 is controlled by the CPU 5a.

Reference numeral 7 is a LUT (look-up table) which outputs the 24-bit full color data stored at the corresponding address using the pixel value of the 8-bit frame memory 6 as an address, and 17 is a computer expanded to 24-bit full color data by the LUT 7. A D / A converter 10 for converting screen data into an analog signal is a display device.

Next, the operation will be described. In this image display device, an image obtained in full color of 8 bits for each of RGB and 24 bits in total is quantized, compressed to less 8-bit gradation information, written in the 8-bit frame memory 6, and then displayed via the LUT 7. Display on 10.

Therefore, first, the analog signal output from the image input device 1 is converted into R,
The G and B signals are converted into digital signals of 8 bits each and a total of 24 bits. At this time, the number of bits in the frame memory is 8
Since it is a bit, the gradation information compression means 14 compresses the 24-bit full color data into 8 bits and outputs the result to 8 bits.
Write to the bit frame memory 6.

The gradation compression processing performed in the gradation information compression means 14 uses a so-called dither method, and the operation principle thereof is shown in FIG. FIG. 2A shows compressed image data, which is one of RGB components of a color image, for example. FIG. 11B shows periodic noise added to the compressed image data, and a noise pattern having a cycle of 4 × 4 pixels is added to the entire compressed image data of FIG. The image of (c) is obtained.
Further, by performing threshold processing on the image shown in FIG. 7C, pixels larger than the threshold are binarized to “1” and pixels smaller than the threshold are binarized to “0”, and one component of the compressed image data is The gradation information of is compressed to 1 bit ((d) in the same figure).

For example, all pixel values of the compressed image data are "0" (brightness is "0", which means black).
In the case of 1, all pixel values are “0” even in the image which is gradation-compressed to 1 bit, which means that the brightness is “0”. Then, as the pixel value of the compressed image data increases, the ratio of “1” in the pixel value of the image that has been gradation-compressed to 1 bit increases.

That is, an image compressed with 1-bit gradation can display only binary values of light and dark for each pixel, but when viewed in an area of a certain size, the average brightness within that area is the compressed image. It is designed to match the brightness of the data.

Next, the noise pattern changing means 15 is used for the gradation information compression processing performed by the gradation information compression means 14 in accordance with the vertical synchronizing signal of the image input apparatus 1, as shown in FIG.
The periodic noise pattern shown in (b) is changed. As a result, the value of noise added to pixels at the same position in the compressed image data changes for each frame or each field. As a result, in addition to expressing the average brightness in a certain area shown in FIG. 2, it is possible to express the brightness by means of temporal averaging as well, and it is possible to improve the expression capability of the brightness.

The periodic noise pattern is not limited to the noise pattern of 4 × 4 pixels shown in FIG. 2B, but various patterns such as a pattern in which the leftmost column is moved to the rightmost column are available. You can think of patterns.

In the embodiment described above, a periodic noise pattern of 4 × 4 pixels is used as shown in FIG. 2, but it goes without saying that it can be generalized to n × n pixels.

Further, although the case of gradation compression to 1 bit has been described for the sake of description, gradation of 2 bits or more can be compressed by applying the well-known idea of the multi-value dither method.

Embodiment 2. FIG. 3 is a block diagram showing an embodiment of the image display device of claim 2. 3, parts that are the same as or correspond to those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted.

In the figure, 31 is gradation information compression means for performing gradation information compression processing on compressed image data using a threshold value that changes periodically, and 32 is threshold pattern changing means for changing the threshold pattern. . In this embodiment, a threshold that changes periodically instead of adding periodic noise to the input image is used to set "1" if each pixel of the compressed image data is larger than the threshold, and "0" if it is smaller than the threshold. Therefore, gradation compression is performed.

FIG. 4 is an explanatory diagram for explaining this operation principle. FIG. 4A shows compressed image data, and FIG. 4B shows a cyclically changing threshold pattern of 4 × 4 pixels.
FIG. 13C shows the result of gradation compression using the threshold pattern shown in FIG.

Next, the operation will be described. In the gradation information compression processing performed by the gradation information compression means 31, a threshold pattern as shown in FIG. 4B is used as a threshold value, and threshold processing is performed on the compressed image data shown in FIG. The gradation number is binarized by performing the gradation compression. On the other hand, the threshold pattern changing means 32 changes the threshold pattern shown in FIG. 4B in synchronization with the vertical synchronizing signal of the image input device.

As a result, in the gradation information compression processing performed by the gradation information compression means 31, the threshold value compared with the pixel at the same position changes for each frame or for each field, so that it is averaged over a certain area. In addition to the original effect of the dither method that expresses the brightness, the brightness is also expressed by the temporal average, and the ability to express the brightness can be improved.

The periodic threshold pattern is not limited to the threshold pattern of 4 × 4 pixels shown in FIG. 4B, but various patterns such as a pattern in which the leftmost column is moved to the rightmost column are available. One can think of threshold patterns.

In the embodiment described above, the periodic threshold pattern of 4 × 4 pixels is used as shown in FIG. 2, but it goes without saying that it can be generalized to n × n pixels.

Further, although the case of gradation compression to 1 bit has been described for the sake of description, gradation of 2 bits or more can be compressed by applying the well-known idea of the multi-value dither method.

Embodiment 3 FIG. 5 is a block diagram showing an embodiment of the image display device of claim 3. 5, parts that are the same as or correspond to those in FIG. 1 are assigned the same reference numerals and explanations thereof are omitted.

In the figure, reference numeral 51 is gradation information compression means for performing gradation information compression processing on compressed image data, and reference numeral 52 is a quantization error generated by gradation compression for one frame or one field and accumulated. It is an error diffusing unit that multiplies the quantization error by an appropriate coefficient and outputs it. Reference numeral 53 is addition means for adding the output of the A / D converter 2 and output of the error diffusion means 52, and 54 is subtraction means for calculating and outputting a quantization error which is the difference between the input and output of the gradation information compression means 51. is there.

Here, in order to clarify the difference between the conventional error diffusion method and this embodiment, the principle of the conventional error diffusion method will be described. Assuming that the pixel value located at the coordinates (x, y) of the image is g (x, y), the gradation information compression means sets the above-mentioned g to the level value Pi having the smallest error with respect to the representable multi-value gradation level. Quantize (x, y). If the quantization error at this time is Ex, y

Ex, y = g (x, y) -Pi (1)

Then, the values of Ex and y are set to the right, the lower right,
Diffuse to the lower pixel, for example, as follows.

That is, in the pixel on the right side, g (x + 1, y) = g (x + 1, y) + Ex, y × 3/8 (2)

In the lower right pixel, g (x + 1, y + 1) = g (x + 1, y + 1) + Ex, y × 1/4 (3)

In the lower pixel, g (x, y + 1) = g (x, y + 1) + Ex, y × 3/8 (4)

Thereafter, similarly, g (x
The smallest error Pi is obtained for (+1, y), and the error is further diffused to the pixels on the right side, the lower right side, and the lower side according to the equations (2), (3), and (4).

If this work is started from the upper left of the image, processed in the order of raster operation, and ended at the lower right of the image,
Similar to the dithering method of the first and second embodiments, the brightness averaged over a certain area of the gradation-compressed image is almost equal to the brightness of the input image, and the gradation is compressed even though the gradation is compressed. Images with high tonal expression ability can be obtained.

While the processing method described above is the conventional error diffusion method, in the present embodiment, the quantization error is diffused to the frame or field that is temporally backward. For example, the pixel value of the coordinate (x, y) in the frame t is gt
As (x, y), the gradation information compression means 51 quantizes the pixel value gt (x, y) into a level Pi having the smallest error in the representable multi-value gradation level. If the quantization error at this time is Ex, y, this quantization error Ex, y can be expressed by the following equation (5).

Ex, y = gt (x, y) -Pi (5)

Then, the quantization error Ex, y is diffused to the same position in the temporally rearward frame and the pixels on the upper, lower, left and right sides, for example, as in the following equations (6) to (10).

That is, for pixels at the same position, gt + 1 (x, y) = gt + 1 (x, y) + Ex, y × 1/2 (6)

Regarding the upper pixel, gt + 1 (x, y + 1) = gt + 1 (x, y + 1) + Ex, y × 1/8 (7)

For the lower pixel, gt + 1 (x, y-1) = gt + 1 (x, y-1) + Ex, y × 1/8 (8)

For the right pixel, gt + 1 (x + 1, y) = gt + 1 (x + 1, y) + Ex, y × 1/8 (9)

For the left pixel, gt + 1 (x-1, y) = gt + 1 (x-1, y) + Ex, y * 1/8 (10)

The above processing is executed for the previous pixel. For this reason, the error diffusion means 52 is used for one frame or
A buffer memory for fields is provided, and the quantization error to be diffused is accumulated in the buffer memory for each pixel. Then, instead of executing the equations (6) to (10), the quantization error accumulated in the buffer memory is added to each pixel value, that is, the output of the A / D converter 2, to adder 53.
Add by.

In this way, in addition to the effect of the conventional error diffusion method in which the quantization error due to the gradation compression processing is diffused to the frame or field that is temporally backward, the average brightness is represented in a certain area. As a result, the brightness can be expressed even with a temporal average, and the ability to express the brightness is improved.

Embodiment 4 FIG. 6 is a block diagram showing an embodiment of the image display device of claim 4. In FIG. 6, parts that are the same as or equivalent to those in FIG.

In the figure, reference numeral 21 is a converting means, which comprises a gradation information compressing means 14 and a noise pattern changing means 15. Image data having gradations of M (M> N) values and a frame synchronization signal or a field synchronization signal are input to the gradation information compression means 14. Also, the conversion means 21
Converts an M-valued image into n-bits so that it can be displayed in N-valued gradations and draws it in the 8-bit frame memory 6.

Embodiment 5 FIG. 7 is a block diagram showing an embodiment of the image display device of claim 5. In FIG. 7, parts that are the same as or correspond to those in FIGS. 3 and 6 are given the same reference numerals and description thereof is omitted.

In the figure, reference numeral 21 is a converting means, which is provided with a gradation information compressing means 31 and a threshold pattern changing means 32 in this embodiment. The gradation information compression means 31 has M
Image data having a gradation of (M> N) value and a frame synchronization signal or a field synchronization signal are input. Further, the conversion means 21 changes the pattern of the threshold value which changes periodically at every predetermined time or every frame period or every field period based on the frame synchronization signal or the field synchronization signal, so that the image of M value becomes N. It is converted into n bits so that it can be displayed in gradation of values and drawn in the 8-bit frame memory 6.

Embodiment 6 FIG. 8 is a block diagram showing an embodiment of the image display device of claim 6. In FIG. 8, parts that are the same as or equivalent to those in FIG.

In the figure, reference numeral 21 is a conversion means, and in this embodiment, a gradation information compression means 51 for performing gradation information compression processing for reducing the number of gradations of an image drawn in the 8-bit frame memory 6. An error diffusion means 52, an addition means 53, and a subtraction means 54 are provided for adding a quantization error resulting from the gradation information compression processing by the gradation information compression means 51 to pixels in a subsequent frame or a subsequent field in terms of time.

The converting means 21 converts gradation information of M value (M> N) into n bits so that it can be displayed in gradation of N value and draws it in the 8-bit frame memory 6 for gradation information compression processing. In addition to the effect of the conventional error diffusion method, which represents the average brightness in a certain area, by adding the resulting quantization error to the pixels in the rear frame or field in time, Brightness and improve the ability to express brightness.

Embodiment 7 FIG. 9 is a block diagram showing an embodiment of the image display device of claim 7. 9, parts that are the same as or correspond to those in FIGS. 1 and 6 are given the same reference numerals and description thereof is omitted.

In this embodiment, the conversion means 21 uses n bits so that the output of the image input device 1 digitized by the A / D converter 2 into m bits / pixel (m> n) can be displayed as N values. And is drawn in the 8-bit frame memory 6.

Embodiment 8 FIG. 10 is a block diagram showing an embodiment of the image display device of claim 8. In FIG. 10, the same or corresponding portions as those in FIGS. 3 and 7 are designated by the same reference numerals and the description thereof will be omitted, but the conversion means 21 including the threshold pattern changing means 32 and the gradation information compression means 31 shown in FIG. The conversion means 21 converts the output of the image input device 1 digitized by the A / D converter 2 into m bits / pixel (m> n) into n bits so that it can be displayed with N values. Drawing in the 8-bit frame memory 6.

Embodiment 9 FIG. 11 is a block diagram showing an embodiment of the image display device of claim 9. In FIG. 11, the same or corresponding parts as those in FIGS. 5 and 8 are designated by the same reference numerals and the description thereof will be omitted, but the gradation information compression means 51 shown in FIG. 5 and the gradation by the gradation information compression means 51 are shown. The conversion means 21 is provided with an error diffusion means 52, an addition means 53 and a subtraction means 54 for temporally adding a quantization error resulting from the information compression processing to pixels in a rear frame or a rear field. It is converted into n bits so that it can be displayed with N values and is drawn in the 8-bit frame memory 6, but it is A / D in m bits / pixel (m> n).
With respect to the output of the image input device 1 digitized by the converter 2, a quantization error resulting from gradation compression is added to pixels in a rear frame or a rear field and temporally diffused to improve image quality.

Embodiment 10 In the embodiments described above, the contents of the LUT 7 have been described as fixed, but the contents are not necessarily fixed, and the LUT 7 may be changed according to the gradation distribution of the image to be displayed. The contents of may be made variable, and in this case, the gradation expression ability can be further improved.

[0083]

As described above, according to the invention of claim 1,
Since the pattern of the periodic noise information is changed every predetermined time, every frame period, or every field period, it is possible to express the gradation of the gradation-compressed image also by the temporal average. There is an effect that it is possible to obtain an image display device capable of suppressing an increase in circuit scale, improving the image quality by improving the gradation expression capability, and preventing deterioration of image quality due to gradation compression.

According to the second aspect of the present invention, the pattern of the threshold value which changes periodically is changed every predetermined time, every frame period or every field period, and the gradation-compressed image of the image is also obtained by temporal averaging. Since it is configured so that gradation expression can be performed, it is possible to suppress an increase in circuit scale, improve image quality by improving gradation expression capability, and prevent deterioration of image quality due to gradation compression. There is an effect that the device can be obtained.

According to the third aspect of the invention, the quantization error resulting from the gradation information compression processing for the image to be gradation-compressed is added to the pixels of the rear frame or the rear field to diffuse the quantization error. Since the gradation expression of the gradation-compressed image can be performed by the temporal averaging, it is possible to suppress the increase in the circuit scale and improve the image quality by improving the gradation expression ability. There is an effect that an image display device capable of preventing deterioration of image quality due to gradation compression can be obtained.

According to the invention of claim 4, the M-value image is gradation-compressed so that it can be displayed together with the n-bit / pixel image from the computer through the same frame memory. At the time of gradation compression, the pattern of periodic noise information is changed every predetermined time, every frame cycle, or every field cycle, and the gradation expression of the gradation-compressed image can be performed by temporal averaging. With this configuration, it is possible to obtain an image display device capable of suppressing an increase in the circuit scale, improving the gradation expression capability during gradation compression, and improving the image quality.

According to the invention of claim 5, the M-value image is gradation-compressed so that it can be displayed together with the n-bit / pixel image from the computer through the same frame memory. In gradation compression, not only is the threshold periodically changed, but the threshold pattern of the threshold is changed at predetermined time intervals, frame intervals, or field intervals, and gradation expression is also performed by temporal averaging. Since it is configured so that it is possible to suppress the increase in circuit scale and improve the gradation expression capability when gradation compression is performed,
There is an effect that an image display device capable of improving image quality can be obtained.

According to the sixth aspect of the present invention, the M-value image is gradation-compressed so that it can be displayed together with the n-bit / pixel image from the computer through the same frame memory. When the gradation is compressed, the quantization error resulting from the gradation information compression processing is temporally added to the pixels in the rear frame or the rear field, and the quantization error is diffused in the time. There is an effect that it is possible to obtain an image display device capable of suppressing the increase and improving the gradation expression ability when gradation compression is performed and improving the image quality.

According to the seventh aspect of the invention, the image digitized into m bits / pixel (m> n) output from the A / D conversion means is gradation-compressed, and the n bits / pixel from the computer is compressed. A pattern of periodic noise information can be displayed together with an image through the same frame memory, and when the image digitized to m bits / pixel is gradation-compressed, a pattern of periodic noise information is generated at predetermined time intervals, frame intervals, or field intervals. Since it is configured so that the gradation expression of the gradation-compressed image can be performed by changing it for each time, the gradation expression ability at the time of gradation compression can be suppressed by suppressing the increase of the circuit scale. And an image display device capable of improving the image quality can be obtained.

According to the eighth aspect of the present invention, the image digitized into m bits / pixel (m> n) output from the A / D conversion means is gradation-compressed, and n bits / pixel from the computer is converted. It is possible to display images together with an image through the same frame memory, and not only cyclically change the threshold value when gradation-compressing the image digitized to m bits / pixel, but also to set the threshold value pattern of the threshold value. Since it is configured so that gradation expression can be performed by temporal averaging by changing it for each time, for each frame cycle, or for each field cycle, it is possible to suppress an increase in the circuit scale and to perform gradation compression. There is an effect that it is possible to obtain an image display device capable of improving the tone expression ability and improving the image quality.

According to the invention of claim 9, the image digitized into m bits / pixel (m> n) output from the A / D conversion means is gradation-compressed, and n bits / pixel from the computer is converted. It is possible to display the image through the same frame memory together with the image, and the quantization error resulting from the gradation information compression processing in the gradation compression of the image digitized to m bits / pixel is temporally delayed in the subsequent frame or In addition to the pixels in the rear field, the quantization error is configured to be diffused in terms of time, thus suppressing an increase in circuit scale,
There is an effect that it is possible to obtain an image display device capable of improving the gradation expression capability in gradation compression and improving the image quality.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram for explaining an operation principle of gradation compression processing by a dither method in the image display device according to the embodiment of the invention of claim 1;

FIG. 3 is a block diagram showing an image display device according to an embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an operation principle when performing gradation compression processing using a threshold pattern in the image display device according to the embodiment of the invention of claim 2;

FIG. 5 is a block diagram showing an image display device according to an embodiment of the invention of claim 3;

FIG. 6 is a block diagram showing an image display device according to an embodiment of the invention of claim 4;

FIG. 7 is a block diagram showing an image display device according to an embodiment of the invention of claim 5;

FIG. 8 is a block diagram showing an image display device according to an embodiment of the invention of claim 6;

FIG. 9 is a block diagram showing an image display device according to an embodiment of the invention of claim 7;

FIG. 10 is a block diagram showing an image display device according to an embodiment of the present invention.

FIG. 11 is a block diagram showing an image display device according to an embodiment of the present invention.

FIG. 12 is a block diagram showing a conventional image display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 image input device 2 A / D converter (A / D conversion means) 6 frame memory 7 LUT (look-up table) 10 display 14, 31, 51, gradation information compression means 15 noise pattern change means 21 conversion means 32 threshold pattern Change means 52 Error diffusion means

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[Procedure amendment]

[Submission date] July 20, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

[0021]

According to the image display device of the present invention, the periodic noise information having a periodic pattern is superimposed on the image information stored in the frame memory, and the periodic noise information pattern is formed at predetermined time intervals. Alternatively, it is possible to perform gradation information compression processing by changing the noise information added to the pixels at the same position by changing it for each frame cycle or field cycle, and to enable gradation expression by temporal averaging. By improving the ability to express
The deterioration of the image quality due to the gradation information compression processing for improving the image quality and suppressing the increase of the device scale is prevented.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0023

[Correction method] Change

[Correction content]

The image display device according to the invention of claim 3 is
When performing the gradation information compression processing to reduce the number of gradations on the image information stored in the frame memory, the quantization error resulting from the gradation information compression processing is temporally transferred to pixels in the subsequent frame or the subsequent field. In addition, since the quantization error is diffused in time, gradation expression can be performed even by temporal averaging, thereby improving the gradation expression capability, thereby improving the image quality and increasing the device scale. The deterioration of the image quality due to the gradation information compression processing for suppressing the increase of the image quality is prevented.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

The image display device according to the invention of claim 5 is
When converting an image with M values (M> N) to n bits so that it can be displayed with N values, not only is the threshold periodically changed, but the threshold pattern of the above threshold is set at predetermined time intervals or frame intervals. It is possible to improve the gradation expression ability by changing it for each field or field cycle so that the gradation expression can be performed by means of temporal averaging.
While improving the quality and suppressing the increase in the scale of the apparatus, the deterioration of the image quality due to the gradation compression is prevented.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

The image display device according to the invention of claim 6 is
When converting an image with M values (M> N) into n bits so that it can be displayed with N values, a quantization error resulting from the gradation information compression processing is temporally added to pixels in a rear frame or a rear field. , By spreading the quantization error over time, the gradation expression ability by temporal averaging is improved.
While improving the image quality and suppressing the increase in the device scale,
Prevents deterioration of image quality due to gradation compression.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

The image display device according to the invention of claim 9 is
When gradation-compressing an image supplied from an image input device digitized into m bits / pixel (m> n) to n bits, a quantization error resulting from the gradation information compression processing is temporally rearwardly framed. Alternatively, in addition to the pixels in the rear field, the quantization error is diffused in time, so that the gradation can be expressed by a temporal average , thereby improving the gradation expression capability, thereby improving the image quality. The deterioration of image quality due to the gradation information compression processing for suppressing the increase in scale is prevented.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction content]

While the processing method described above is the conventional error diffusion method, in the present embodiment, the quantization error is diffused to the frame or field that is temporally backward. For example, the pixel value of the coordinate (x, y) in the frame t is g _t
As (x, y), the gradation information compression means 51 quantizes the pixel value g _t (x, y) into a level Pi having the smallest error in the representable multi-value gradation level. If the quantization error at this time is Ex, y, this quantization error Ex, y can be expressed by the following equation (5).

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0062

[Correction method] Change

[Correction content]

Ex, y = g _t (x, y) −Pi (5)

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0064

[Correction method] Change

[Correction content]

That is, for pixels at the same position, g _{t + 1} (x, y) = g _{t + 1} (x, y) + Ex, y × 1/2 (6)

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0065

[Correction method] Change

[Correction content]

For the upper pixel, g _{t + 1} (x, y + 1) = g _{t + 1} (x, y + 1) + Ex, y × 1/8 (7)

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0066

[Correction method] Change

[Correction content]

For the lower pixel, g _{t + 1} (x, y-1) = g _{t + 1} (x, y-1) + Ex, y × 1/8 (8)

[Procedure Amendment 11]

[Document name to be amended] Statement

[Correction target item name] 0067

[Correction method] Change

[Correction content]

For the right pixel, g _{t + 1} (x + 1, y) = g _{t + 1} (x + 1, y) + Ex, y × 1/8 (9)

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

For the left pixel, g _{t + 1} (x-1, y) = g _{t + 1} (x-1, y) + Ex, y × 1/8 (10)

[Procedure Amendment 13]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

Claims (9)

[Claims] 1. An image display device for displaying color or monochrome image information on a display via a frame memory, wherein periodic noise information having a periodic pattern is superimposed on the image information stored in the frame memory. Gradation information compressing means for performing gradation information compression processing to reduce the number of gradations, and noise pattern changing means for changing the pattern of the periodic noise information at predetermined time intervals, frame intervals, or field intervals. An image display device comprising: 2. An image display device for displaying color or black and white image information on a display via a frame memory, and gradation information compression processing for reducing the number of gradations in the image information stored in the frame memory. Gradation information compression means for periodically changing the threshold value when performing
An image display device, comprising: a threshold pattern changing unit that changes the threshold pattern of the threshold value that changes periodically every predetermined time, every frame cycle, or every field cycle. 3. A gradation information compression process for reducing the number of gradations in the image information stored in the frame memory in an image display device for displaying color or monochrome image information on a display through a frame memory. Grayscale information compression means for performing the above, and error diffusion means for adding a quantization error resulting from the grayscale information compression processing by the grayscale information compression means to a pixel of a rear frame or a rear field in terms of time. Image display device. 4. An image display device for displaying color or black and white image information on a display, and an n-bit / pixel frame memory which can be directly drawn from a computer, and a floor which can display the contents of the frame memory on the display. Look-up table that develops to gradations of N values (N ≦ 2 ⁿ ) that is a subset of keys, and M values (M> N)
Of the image is converted into n bits so that it can be displayed in the gradation of the N value and is drawn in the frame memory, and the converting means is cyclic to the image stored in the frame memory. Grayscale information compression means for performing grayscale information compression processing for superimposing periodic noise information having a pattern to reduce the number of grayscale levels, and a pattern of the periodic noise information for every predetermined time or frame period or field. An image display device, comprising: a noise pattern changing unit that changes each cycle. 5. An image display device for displaying image information such as color or black and white on a display, and an n-bit / pixel frame memory which can be directly drawn from a computer, and a floor which can display the contents of the frame memory on the display. Look-up table that develops to gradations of N values (N ≦ 2 ⁿ ) that is a subset of keys, and M values (M> N)
Of the image described above is converted into n bits so that it can be displayed in the gradation of N values, and the conversion means draws in the frame memory, and the conversion means further includes the gradation of the image drawn in the frame memory. The gradation information compressing means for cyclically changing the threshold value when performing the gradation information compression processing for reducing the number, and the pattern of the cyclically changing threshold value for each predetermined time, frame cycle, or field cycle. An image display device, comprising: 6. An image display device for displaying color or black-and-white image information on a display, and an n-bit / pixel frame memory which can be directly drawn from a computer, and a floor which can display the contents of the frame memory on the display. Look-up table that develops to gradations of N values (N ≦ 2 ⁿ ) that is a subset of keys, and M values (M> N)
Of the image described above is converted into n bits so that it can be displayed with the gradation of N values and is drawn in the frame memory, and the converting means is the number of gradations of the image drawn in the frame memory. Gradation information compression means for performing gradation information compression processing for reducing the noise, and an error in which a quantization error resulting from the gradation information compression processing by the gradation information compression means is temporally added to a pixel in a rear frame or a rear field. An image display device comprising: a diffusion unit. 7. An image display device capable of synthesizing and displaying a color or black and white image supplied from an image input device or a computer on a display, and an n-bit / pixel frame which can be directly drawn from the computer. The memory and the N value (N
Look-up table developed to gradations of ≤2 ⁿ ), A / D conversion means for digitizing the image supplied from the image input device into m bits / pixel (m> n), and its A / D conversion And a conversion means for converting the m-bit output of the means into n bits so that it can be displayed with the N value and drawing it in the frame memory, and the conversion means cyclically applies to the image stored in the frame memory. Gradation information compression means for performing gradation information compression processing to reduce the number of gradations by superimposing periodic noise information having a specific pattern, and the pattern of the periodic noise information at predetermined time intervals or frame intervals. Alternatively, the image display device is provided with a noise pattern changing unit that changes each field period. 8. An image display device capable of synthesizing and displaying a color or monochrome image supplied from an image input device, a computer or the like on a display, and a frame of n bits / pixel which can be directly drawn from the computer. The memory and the N value (N
Look-up table developed to gradations of ≤2 ⁿ ), A / D conversion means for digitizing the image supplied from the image input device into m bits / pixel (m> n), and its A / D conversion And a conversion means for converting the m-bit output of the means into n bits so that it can be displayed with the N value and drawing it in the frame memory, and the conversion means further has gradation of an image drawn in the frame memory. The gradation information compression means for cyclically changing the threshold value when performing the gradation information compression processing for reducing the number, and the pattern of the cyclically changing threshold value for each predetermined time, frame cycle, or field cycle. An image display device, comprising: 9. An image display device capable of synthesizing and displaying a color or black-and-white image supplied from an image input device, a computer or the like on a display, and an n-bit / pixel frame which can be directly drawn from the computer. The memory and the N value (N
Look-up table developed to gradations of ≤2 ⁿ ), A / D conversion means for digitizing the image supplied from the image input device into m bits / pixel (m> n), and its A / D conversion And a conversion means for converting the m-bit output of the means into n bits so that it can be displayed with the N value and drawing it in the frame memory, and the conversion means further comprises a floor of the image drawn in the frame memory. Grayscale information compression means for performing grayscale information compression processing to reduce the number of tones, and a quantization error resulting from the grayscale information compression processing by the grayscale information compression means is temporally distributed to pixels in a rear frame or a rear field. An image display device comprising: an error diffusion unit for adding.