JP2000298460A - Picture display method and picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable displaying high quality picture in which arch-fact is not caused and visual flicker is suppressed by making picture data of time division display after converting picture data to picture data of integral multiple of the number of time division, when a rate of picture data is substantially a threshold value or more. SOLUTION: In a data conversion section 26 of a data processing section 16, when a rate of the same picture data is the prescribed threshold value or more in accordance with a rate of substantially the same picture data in the prescribed region, after picture data is converted to data of a multiple of frame numbers of time division, picture data of time division display is obtained. When a rate of the same picture data is a threhold value or less. picture data of ordinary time division display is obtained. Therefore, in the case of that picture display is performed with lower bit numbers than that of supplied picture data, even when it is picture display of high luminance, flicker is not visual, and arch-fact is not displayed, and picture display of high gradation and high quality can be performed without improving a frame frequency largely.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of image display on a liquid crystal display, a CRT (Cathode Ray Tube) or the like, and more specifically, displays an image of high-resolution image data exceeding the gray scale resolution of display. In particular, the present invention relates to an image display method and an image display apparatus capable of displaying a high-quality image free from artifacts and flicker.

[0002]

2. Description of the Related Art MRI diagnostic apparatus, X-ray diagnostic apparatus, FCR
A diagnostic image taken by a medical measuring device such as (Fuji Computed Radiography) is usually recorded on a light-transmitting image recording film such as an X-ray film or a film photosensitive material, and is used as a light-transmitting image. Will be played. The film on which the diagnostic image has been reproduced is set on a light source device called a shakasten, and is observed in a state where light is emitted from the back surface, and diagnosis is performed. In addition, the medical measurement device usually has a monitor (display) such as a CRT or a liquid crystal display (LCD) for observing a taken diagnostic image, or is connected to a monitor, and an image output to the monitor is provided. , A check of a diagnostic image before film output, adjustment, image processing, and the like.

When a diagnostic image measured by a medical measuring device is reproduced on a film, the image is usually reproduced with a gradation resolution of 10 bits. On the other hand, CRTs normally display with 8-bit gradation resolution, and LCDs
In this case, display is normally performed with 6-bit, high-performance 8-bit gradation resolution. In the LCD, there is no driver IC exceeding 8 bits at present. That is, in any of the monitors, an image is displayed using so-called bit-dropped image data having a lower gradation resolution than image data output from the medical measurement device.

Normal 100 cd / m ^{2 to} 200 cd / m
^{When an} image is displayed with a luminance of about ² , there is no problem in displaying an 8-bit image with the bits dropped. However, when the display luminance of an image increases, the luminance resolution of the eyes (light / dark discrimination ability) increases, and contour artifacts (false contours) due to bit omission may occur, which may be a problem.

For example, in a medical diagnostic image as described above, since a diagnosis is made based on a density difference between monochrome images, it is required that a fine density difference can be discriminated even in a high density region exceeding a density of 2. In order to make this possible, the above-mentioned Schakkasten emits very high-intensity light (for example, 3000 cd / m ² or more in JIS standard), and a high-intensity light equivalent to a monitor of a medical measuring device is used. Display of a unique image is required. Moreover, in medical applications, an error in visual recognition of an image leads to an erroneous diagnosis, so that a very high-quality image is required. Therefore, in the monitor of the medical measuring device, the artifact caused by the bit drop becomes a serious problem.

On the other hand, as a means for solving the problem of image display due to such bit omission, time division (FRC = Fram
e Rate Control) display is known. The time-division display is, for example, a method in which 10-bit image data is divided into four to form 8-bit image data, and this is sequentially displayed, so that 8-bit and 10-bit gradation expression is performed. . Here, when displaying an image in a time-division manner, flicker (flickering of the image) due to time-division of the image becomes a problem.

In order to eliminate flicker, it is necessary to increase the frame frequency of time-division display for display and perform high-speed display switching. However, the response speed of the monitor driver IC and the monitor itself is limited. In particular, as in the medical applications described above, high-definition image display for high image quality, for example,
When an image is displayed by QSXGA (2560 pixels × 2048 pixels) and the number of pixels increases, it is very difficult to cope with the problem.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an image with a lower gradation resolution than the gradation resolution of image data supplied from an image data supply source. When performing display, time-division display eliminates the occurrence of artifacts, makes the gradation resolution and luminance resolution substantially the same as the supplied image data, and suppresses the visibility of flicker without greatly improving the frame frequency. An object of the present invention is to provide an image display method capable of displaying a high-quality image, and an image display device using the image display method.

[0009]

To achieve the above object, an image display method according to the present invention provides a method for receiving image data having a higher gradation resolution than a display gradation resolution from an image data supply source and displaying the image data. In accordance with the difference in the gradation resolution between the display and the image data, the supplied image data is converted into image data for time-division display, and the ratio is determined in accordance with the ratio of substantially the same image data in a predetermined area. Is greater than or equal to a predetermined threshold, after converting the image data in the predetermined area to image data of an integral multiple of the number of time divisions, an image display method characterized by time-division display image data. provide.

An image display device according to the present invention is an image display device for receiving and displaying image data having a higher gradation resolution than a display gradation resolution from an image data supply source. Detecting means for detecting a ratio of substantially the same image data in a predetermined area of the image data; and, if the ratio is less than a predetermined threshold, according to a detection result by the detecting means, an image of the area is determined. The data is time-division display image data according to the difference in the gradation resolution between the display and the image data.If the ratio is equal to or greater than a predetermined threshold, the image data of the area is an integral multiple of the number of time divisions. A data processing unit for converting the image data into image data of a time-division display, and supplying the image data processed by the data processing unit to the display unit. To provide an image display device characterized by having a stage.

Further, in the image display apparatus of the present invention, it is preferable to receive 10-bit image data from an image data supply source, convert this image data into 8-bit image data by time-division display, and perform image display. A display device is provided.

Further, in the image display device of the present invention,
Maximum display brightness is 500 cd / m ^{2 to} 5000 cd / m
Preferably it is ² .

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image display method and an image display apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a conceptual diagram showing an example in which an image display device using the image display method of the present invention is used as a monitor of a medical measuring device. The display device 10 shown in FIG.
A liquid crystal display (hereinafter, referred to as an LCD) displays a liquid crystal image on the liquid crystal panel 12, a backlight unit 14, a data processing unit 16, a driver 18 of the liquid crystal panel 12, an interface 22 (hereinafter, an I / F 22). ).

In the illustrated display device 10, an I / F
A medical measurement device R (hereinafter, referred to as a measurement device R) such as an MRI diagnostic device, an X-ray diagnostic device, or an FCR, which serves as a supply source of a diagnostic image, is connected via the diagnostic image sensor 22 to supply image data and the like. . Here, in the illustrated example, image data with a gradation resolution of 10 bits (bit) is supplied from the measuring device R, but the display device 10 displays an image with a gradation resolution of 8 bits. Yes, as will be described in detail later, the image processing for that purpose is performed by the data processing unit 16.

It should be noted that the present invention is not limited to the LCD shown in the drawings, but includes a digital micromirror device (DMD) display and an electrochromic display (EC).
D), electrophoretic display (EPID), CRT, plasma display (PDP), fluorescent display tube (VF)
D), light emitting diode (LED) display, electroluminescent (EL) display, field emission display (FE)
D) and various known display devices such as an organic EL display.

In the LCD utilizing the present invention, there is no particular limitation on the liquid crystal panel 12, and a liquid crystal is filled between transparent supports arranged with a predetermined gap, and a transparent electrode is provided. All known liquid crystal panels used for various LCDs, in which polarizing plates are arranged on both sides of a sheet, can be used. Therefore, the liquid crystal panel 12 (the display device 1 of the present invention)
0) may be color or monochrome, and the operation mode is TN (Twisted Nematic) mode, STN (Super T
wisted Nematic) mode, ECB (Electrically Control)
lled Birefringence) mode, IPS (In-Plane Swichi)
ng) mode, MVA (Multi-domain Vertical Alignemen)
All operation modes such as the t) mode can be used, and there is no limitation on the switching elements and the matrix.

The backlight unit 14 emits a backlight for observing an image displayed on the liquid crystal panel 12, and is similar to a backlight unit of a known LCD. The display device of the present invention has a maximum luminance of 500 cd / m2 so that it can be suitably used for a monitor for medical use.
^It is preferable that a display of ^{2 to} 5000 cd / m ² is possible, and it is preferable that the backlight unit 14 selects and sets the type of light source, the number of light sources, and the like so as to realize this.

In the display device 10 of the illustrated example,
If necessary, in order to increase the viewing angle of the LCD, a diffusion plate may be arranged on the observation surface side of the liquid crystal panel 12 and a collimator plate may be arranged on the opposite side.

In the display device 10 shown in the figure, the 10-bit image data supplied from the measuring device R includes an I / F 2
2 to the data processing unit 16. The data processing unit 16 converts the supplied 10-bit image data into a time-division (FRC = Fr) image corresponding to the image display by the display device 10.
(Ame Rate Control) This is a part that converts the data into 8-bit image data by display and supplies it to the driver 18 of the liquid crystal panel 12.

FIG. 2 shows a block diagram of the data processing section 16. In the illustrated example, the data processing unit 16 includes a 10-bit frame memory (hereinafter, referred to as FM) 24, a data conversion unit 26, and 8-bit FMs 28a, 28b, 28.
c and 28 d, and a switching unit 30. I / F2
10-bit image data supplied from the FM2
And then read by the data converter 26,
The data is converted into 8-bit image data for time-division display.

As is well known, the time-division display is used to display image data having a high bit number (gradation resolution) from image data having a high bit number, when displaying image data having a low bit number. A plurality of (number of frames = number of time divisions) image data having a low number of bits corresponding to the difference is generated, and this image data is sequentially displayed, so that an image display having a low number of bits corresponds to a high number of bits. In this method, an image without artifacts is displayed even if the luminance is high. For example, when the difference in the number of bits is n, image data having a low number of bits of 2 ⁿ frames is generated, and the image data is sequentially displayed. More specifically, 8
Since four bits correspond to 10-bit data, as shown in FIG.
When performing time-division display with bits, 10-bit image data is sequentially displayed as 8-bit image data of four frames, and this image data is sequentially displayed to perform 10-bit gradation expression.

Here, when the time-division display is performed, the occurrence of artifacts can be prevented. However, if the image of the divided image data is not switched quickly, that is, unless the frame frequency is increased, flicker (image flickering) will occur. (With flicker)
Occurs. On the other hand, in the present invention, the calculation method of the image data for performing the time-division display is changed according to the ratio of substantially the same image data included in the predetermined area.
In other words, the method of calculating the image data for performing the time-division display is changed according to the ratio of the substantially same density in the predetermined area. As a result, even without increasing the frame frequency, the occurrence of flicker is prevented, that is, a flickerless high-gradation image can be displayed.

As described above, a 10-bit image display is as follows.
It can be represented by time-division display of 8 bits × 4 frames. That is, as shown in FIG. 3, the 10-bit image data 8 is composed of 8 frames of “2, 2, 2, 2”.
It can be represented by bit image data. Similarly, image data 9 is image data of “3, 2, 2, 2” and image data 1
0 is image data of “3, 2, 3, 2”, and image data 1
Reference numeral 1 denotes image data of “3, 3, 3, 2”, which can be expressed respectively.

In general, when displaying a black-and-white image having a relatively high luminance, such as a medical diagnostic image, flicker is visually recognized when the visible period (time repeating unit) is less than 60 Hz. Is done. For example, when the example shown in FIG. 3 is a still image and the frame frequency V is 60 Hz, in the image data 8, the visible period is 1 V and 60
Hz, the flicker is not visually recognized. On the other hand, the cycle of the image data 9 is 15 Hz at 4 V, the cycle of the image data 10 is 30 Hz at 2 V, and the cycle of the image data 11 is 15 Hz at 4 V. In any case, flicker is visually recognized.

According to the study of the present inventor, although flicker is easily recognized in a region where the QL value is constant, that is, in a region where the image data is constant (so-called solid image) in a certain area, various flickers are detected. Are mixed in a small area, that is, when various types of image data are mixed, flickers cancel each other out and are not visually recognized. For example, in the case of a medical diagnostic image, flicker is not visually recognized in a region of an actual image in which various densities necessary for diagnosis are mixed in a small area, even if the visible frequency is less than 60 Hz.

The present invention utilizes this, and
The data conversion unit 26 converts the image data into a time-division frame number (in the illustrated example, if the ratio of the same image data is equal to or more than a predetermined threshold) in accordance with the ratio of the substantially same image data in the predetermined area. After converting 10 bits into a multiple of 8 bits of 4 frames), the image data is time-division display image data. Otherwise, the image data is normally time-division display image data. In other words, a portion where the ratio of the substantially same image data is large is a portion that is not related to diagnosis such as an X-ray missing portion, and this portion is displayed without increasing the gradation,
The portion where various image data are mixed is a portion related to diagnosis, and this portion is to be displayed in high gradation. Hereinafter, a more detailed description will be given with reference to FIG.

The example shown in FIG. 4 is a 15-pixel × 15-pixel image having a total of 255 pixels, with the area shown by the dotted line as one pixel, and the area shown by the diagonal lines is a real image and various image data are stored. The same image data is mixed, and the rest is the background. The data conversion unit 26 reads the image data from the FM 24, divides this image into 15 regions using, for example, a mask of 3 pixels × 3 pixels as indicated by a solid line, and substantially within each region. A ratio indicated by the same image data is detected, and it is determined whether the ratio is equal to or greater than a threshold. For example, assuming that the threshold value is all pixels (100%), the area indicated by the bold line is the same image data for all images and is equal to or larger than the threshold value.

If the image data read from the FM 24 is image data of an area (mask) in which the ratio of substantially the same image data is less than the threshold, the data conversion unit 26 performs the normal time division display. Similarly, image data is generated. In the illustrated example, since 10-bit image data is 8-bit image data for performing time-division display, for example,
If the 10-bit image data supplied from the measurement device R (I / F 22) is 511, “128, 12
8, 128, 127 "is 8-bit image data. Therefore, an accurate image is displayed with appropriate image data in an important area including a real image where flicker is not visually recognized.

On the other hand, if the image data read from the FM 24 is the image data of a region where the ratio of substantially the same (same in the illustrated example) image data as indicated by the bold line is equal to or larger than the threshold value, The data conversion unit 26 converts the image data into a multiple of the number of time-division frames, and then converts the image data into time-division image data. Specifically,
When the supplied 10-bit image data is 511, the image data is first converted to a multiple of 4 which is the number of frames,
For example, after being converted into 10-bit image data 512, the image data is converted into 8-bit 4-frame image data of “128, 128, 128, 128”. Similarly, when the 10-bit image data is 258, for example, after converting to 10-bit image data 256, “64, 64,
It is assumed that the image data is 4 frames of 64 bits, 8 bits. In other words, all frames are set as the same image data, thereby preventing a reduction in the period that is visually recognized by time-division display, and preventing the occurrence of flicker.

Therefore, according to the present invention, when an image is displayed with a bit number lower than that of the supplied image data, even if the image is displayed with high luminance, the flicker is not greatly improved without greatly improving the frame frequency. Can be displayed without causing artifacts, without artifacts, and with high gradation and high image quality.

Here, in the present invention, substantially the same image data is image data having the same upper bits corresponding to the resolution that can be actually displayed in time-division image display. Therefore, when “resolution of image data = resolution of display × number of frames” as in the above-described example, “substantially the same image data = the same image data”. On the other hand, when the resolution of the supplied image data is high and cannot be time-divided in the display device 10, that is, when “resolution of image data> resolution of display × number of frames”, substantially the same image is displayed. The data is a wider range of image data including the same image data.

For example, when the image data supplied from the measuring device R (I / F 22) is 12 bits, and the display device 10 performs time-division display with 4 frames of 8 bits in the same manner as above, the supplied image data is supplied. It is not possible to display the image data completely in a time-division manner (flicker becomes too low frequency).

In this case, since the display device 10 performs 10-bit image display, it is not possible to represent the lower two bits of the gradation of the 12-bit image data supplied from the measuring device R. Can not. Therefore, in the present invention, if the upper bits corresponding to the resolution that can be actually displayed (gradation expression) in the time-division image display excluding the portion where gradation cannot be expressed are the same image data, the present invention regards the same image data. That is, the image data becomes substantially the same. In this example, since the 12-bit image data is displayed in 10 bits, the 12-bit image data having the same upper 10 bits is substantially the same image data. In other words, the integer of the solution divided by the amount corresponding to the difference m between the number of bits of the supplied image data and the number of bits in the time-division display (= “2 ^m ”, which is 2 in this example, is 4) is The same image data is substantially the same image data.

Accordingly, the data conversion unit 26 detects the ratio of substantially the same image data in response to this, and as described above, the ratio of substantially the same image data within the predetermined area is equal to or larger than the threshold value. In this case, the image data of the area is converted to a multiple of the number of time-division frames, and then converted to time-division image data.

In the present invention, there is no particular limitation on the size of the predetermined area for detecting the ratio of substantially the same image data, that is, the mask size in the example shown in FIG.
For example, the size (area) of one pixel may be determined as appropriate according to the size of one pixel, but it is preferable that the area (mask size) be smaller as the size (area) of one pixel is larger. Further, there is no particular limitation on the threshold value of the ratio of substantially the same image data at which the image data is converted to a multiple of the number of frames, and may be appropriately determined according to the luminance, the frame frequency, the pixel size, and the like.

In this embodiment, the conversion of 10-bit image data to 8-bit time-division display image data is not limited. For example, as described above, 12-bit image data is converted to 8-bit image data. , Or 12-bit image data may be used as 10-bit time-division display image data, or 8-bit image data may be used as 6-bit time-division display image data.

The 8-bit image data of the time-division display calculated by the data conversion unit 26 is sequentially converted to FMs 28a to 28d.
Sent to and stored. The switching units 30 connect the FMs 28a to 28d to the driver 18 at a predetermined timing according to the frame frequency, and the stored image data is sequentially supplied to the driver 18 at a predetermined timing.

The driver 18 drives the liquid crystal panel 12 according to the supplied image data to display an image. As described above, this image has a gradation (luminance) resolution equivalent to 10 bits supplied from the measuring device R, and is a high-quality image in which artifacts and flicker are not visually recognized. .

Although the image display method and the image display device of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the gist of the present invention. Of course, you can do it.

[0041]

As described above in detail, according to the present invention, when an image is displayed at a gradation resolution lower than the gradation resolution of the image data supplied from the image data supply source, the display luminance is reduced. Even if the image quality is improved, it is possible to display a high-quality image in which artifacts are not generated by the time-division display and flicker is suppressed without significantly improving the frame frequency.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an example in which an image display device of the present invention is used as a monitor of a medical measurement device.

FIG. 2 is a block diagram of a data processing unit of the image display device shown in FIG.

FIG. 3 is a timing chart for explaining the image display method of the present invention.

FIG. 4 is a conceptual diagram illustrating an image display method according to the present invention.

[Explanation of symbols]

Reference Signs List 10 display device 12 liquid crystal panel 14 backlight unit 16 data processing unit 18 driver 22 I / F (interface) 24 10-bit FM (frame memory) 26 data conversion unit 28a, 28b, 28c, 28d 8-bit FM (frame memory) ) 30 Switching unit

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G09G 3/20 641 G09G 3/36 3/36 H04N 5/66 A 5/36 A61B 5/05 380 H04N 5/66 G09G 5/36 520A

Claims (4)

[Claims] When receiving image data having a higher gradation resolution than a display gradation resolution from an image data supply source and displaying the received image data, the supplied image data is provided in accordance with a difference in the gradation resolution between the display and the image data. When the data is time-division display image data and the ratio is equal to or more than a predetermined threshold value in accordance with the ratio of substantially the same image data within the predetermined region, the image data within the predetermined region is converted to the image data at the time. An image display method characterized by converting image data into an image data of an integral multiple of the number of divisions and then converting the image data into time-division display image data. 2. An image display device for receiving image data having a higher gradation resolution than a display gradation resolution from an image data supply source and displaying the image data, comprising: an image display means; Detecting means for detecting the ratio of substantially the same image data, and according to the detection result by the detecting means, when the ratio is less than a predetermined threshold, the image data of the area is the display and image data In the case of the time-division display image data according to the difference of the gradation resolution, if the ratio is equal to or greater than a predetermined threshold, after converting the image data of the area to image data that is an integral multiple of the number of time divisions, Similarly, the image processing apparatus further includes a data processing unit that converts the image data into time-division display image data, and a supply unit that sequentially supplies the image data processed by the data processing unit to the display unit. Image display device. 3. A 10-bit image data is received from an image data supply source, and the image data is converted to an 8-bit image by time-division display.
3. The image display device according to claim 2, wherein the image display is performed using bit image data. 4. The display has a maximum luminance of 500 cd / m ² to 50.
The image display device according to claim ² , wherein the image display device is 00 cd / m ² .