JP2002174806A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device using a liquid crystal display, wherein the display image is easy to watch regardless of the brightness of environment (surrounding light). SOLUTION: The image display device has the liquid crystal display provided with a backlight and a backlight controlling means for brightening the backlight of the liquid crystal display when the environmental light is bright but darkening the backlight when the environmental light is dark so that the leakage light (minimum luminance) determined by the extinction ratio of a liquid crystal does not exceed a prescribed level.

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, and more specifically, to an image display device using a liquid crystal display device, and the back of the liquid crystal display device according to the brightness of ambient light (ambient light). The present invention relates to an image display device that adjusts the brightness of a light to make a display image easier to see.

[0002]

2. Description of the Related Art In the medical field, X
2. Description of the Related Art Various diagnostic image acquisition apparatuses using X-rays and the like have been used, such as X-ray imaging apparatuses, CR (Computed Radiography) apparatuses, CT (Computed Tomography) apparatuses, and MRI (Magnetic Resonance Imaging). ) Devices have been put to practical use.

[0003] Medical image information obtained by these devices is recorded on a photographic film, observed on a Schaukasten or recorded on another recording medium, and then subjected to desired image processing such as frequency processing and gradation processing. After being processed, it is displayed on an image display device (monitor screen) and observed, so that it is used for diagnosis or the like at a medical site.

[0004] Conventionally, as the above-mentioned image display device, CR
Although a T display device has been used, recently, a so-called flat panel display using a liquid crystal panel, an organic EL panel, or the like is about to be used. This flat panel display generally has advantages such as space saving, light weight, and low power consumption as compared with a CRT display device, and is considered to be further popularized in the future.

[0005] A CR (computed radiography) device is a device in which a part of radiation energy is accumulated by irradiation of radiation, and then irradiated with excitation light such as visible light or infrared light. Radiation image information of a subject such as a human body is recorded on a stimulable phosphor (stimulable phosphor) that emits stimulable light in accordance with the accumulated radiation energy, and the radiation image information is stored in the stimulable phosphor. By detecting the luminescent light, it is read photoelectrically, an image signal is obtained, the obtained image signal is subjected to image processing, and a soft copy image is outputted to an image display device, or a hard copy image is outputted to an X-ray photographic film. This is a radiation image recording / reading device that outputs an image.

A CT (computed tomography) apparatus uses a computed tomography method, in which projected images of a parallel beam on a straight line by X-rays are obtained at various angles, and the data are obtained. The X-ray absorptance of the internal tissue, that is, the tissue structure, is obtained by calculation from, and is output as a soft copy image or a hard copy image. Reconstruction from projected images includes successive approximation,
There are methods such as back projection.

An MRI (Magnetic Resonance Imaging) apparatus is usually an apparatus for extracting and imaging an electromagnetic wave signal generated by a nuclear magnetic resonance effect of a hydrogen atom.
Specifically, an electromagnetic wave having a natural resonance frequency of a nucleus is applied from the outside to set a nuclear magnetic moment derived from spin to an excited state, and when the above-described electromagnetic wave is stopped from this state, the excited nucleus becomes a ground state. The electromagnetic wave of the resonance frequency is emitted in the process, and the electromagnetic wave is received by a coil, imaged, and output as a soft copy image or a hard copy image.

[0008]

By the way, in a display device using the above-mentioned liquid crystal panel, even if the backlight of the liquid crystal is completely turned off, some light leaks (so-called leak light). There is a problem that the appearance of the displayed image changes depending on the external light and the ambient light.

This problem is irrelevant when the image is viewed in a bright place, but becomes very difficult when the image is slightly dark. Specifically, in a slightly dark viewing environment, light from the liquid crystal panel leaks, resulting in an image with reduced contrast.

On the other hand, in principle, the backlight of the liquid crystal is brightened when the ambient light is bright, thereby brightening the low-density portion to make the image easy to see. It is only necessary to make the backlight darker, but in this case, it is necessary to consider the leakage light determined by the extinction ratio of the liquid crystal.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to solve the problems in the prior art, and to provide an image display device using a liquid crystal display device with environmental light (ambient light). It is an object of the present invention to provide an image display device which makes it possible to make a display image truly easy to see regardless of the brightness of the image.

[0012]

In order to achieve the above object, an image display device according to the present invention comprises a liquid crystal display device having a liquid crystal display device and a backlight. Backlight control means for brightening the backlight of the liquid crystal display device and, when ambient light is dark, darkening the backlight so that leakage light (minimum luminance) determined by the extinction ratio of the liquid crystal does not exceed a certain value. It is characterized by.

Here, the backlight control means includes means for detecting the brightness of the ambient light and means for controlling the brightness of the backlight of the liquid crystal display device, wherein Preferably, the brightness of the backlight is adjusted.

[0014] Further, the means for controlling the brightness of the backlight is provided in the backlight, and means for detecting the brightness value of the backlight, and means for detecting the brightness value of the backlight and the extinction of the liquid crystal. Means for estimating the luminance a of the leakage light of the liquid crystal screen from the relationship with the leakage light determined by the ratio;
From the brightness of the ambient light detected by the means for detecting the brightness of the ambient light, based on the relationship between the brightness of the ambient light previously determined and the brightness b due to the reflection of the liquid crystal screen corresponding thereto, Means for calculating a brightness b due to reflection of the liquid crystal screen corresponding to the brightness of the ambient light, and controlling the brightness of the backlight so that the brightness a is not more than twice the brightness b. Preferably, there is.

The means for controlling the brightness of the backlight is based on a relationship between a predetermined backlight luminance value and leakage light determined by an extinction ratio of the liquid crystal. Means for estimating the luminance a of the leakage light of the liquid crystal screen from the current backlight brightness estimated based on the relationship between the use time of the light and the light emission luminance and the relationship between the backlight control signal and the light emission luminance; From the brightness of the ambient light detected by the means for detecting the brightness of the ambient light, based on the relationship between the brightness of the ambient light previously determined and the brightness b due to the reflection of the liquid crystal screen corresponding thereto, Means for determining a brightness b due to reflection of the liquid crystal screen corresponding to the brightness of the ambient light, and controlling the brightness of the backlight so that the brightness a is not more than twice the brightness b. That it is preferable that the.

Further, the means for controlling the brightness of the backlight is such that the brightness of the backlight is at least 70% of the maximum brightness of the backlight within a range where the brightness a is not more than twice the brightness b. It is preferable to control so that More preferably, the means for controlling the brightness of the backlight may control the brightness a so as to be equal to or less than the brightness b. Also, the means for controlling the brightness of the backlight controls the brightness of the backlight to be 70% or more of the maximum brightness of the backlight within a range where the brightness a is equal to or less than the brightness b. Is preferred.

In this specification, the term “ambient light” refers to light existing in an environment in which the image display device according to the present invention is installed.
Ambient light). Also, “bright” is a state with a lot of light in the above-described environment, and “dark” is a state opposite to the above. Further, the brightness of the backlight is used synonymously with the brightness of the backlight, and has no direct relation to the brightness of the environment. Further, the extinction ratio is a ratio of light that leaks when the liquid crystal is completely turned off, and is indicated by a ratio between a completely on state and a completely off state.

[0018]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a schematic configuration of an image display device 30 according to an embodiment of the present invention.
3 is a block diagram showing a schematic configuration of a control system including a controller 36 of the image display device 30 according to the present embodiment.
1 and 2, reference numeral 10 denotes a liquid crystal display panel which is a main part of an image display device 30 according to the present embodiment, 12 denotes a liquid crystal display panel of the liquid crystal display panel 10, and 20 denotes a back of the liquid crystal display panel 10. A light 32, a backlight monitor provided in a part of the backlight 20,
Is an external light monitor for detecting external light in the environment where the image display device 30 is installed, and 36 is whether or not to adjust the brightness of the backlight based on monitor signals from the backlight monitor 32 and the external light monitor 34 And 38, a backlight control device that controls the output of the backlight 20 based on the backlight adjustment signal from the controller 36.

In the controller 36 shown in FIG. 2, reference numeral 40 denotes external light (ambient light) detected by the external light monitor 34.
An external light reflection luminance estimating unit 44 for estimating the luminance b due to external light reflection of the liquid crystal screen of the liquid crystal display panel unit 10 based on the brightness (monitor value) of the backlight 20 detected by the backlight monitor 32. A light leakage luminance estimating unit 42 for estimating the luminance (minimum luminance) a of the light leakage from the liquid crystal screen, and a leakage light luminance estimating unit 44 and an external light reflection luminance estimating unit 40
A backlight adjustment signal generation unit that generates a backlight adjustment signal from the luminance a and the luminance b obtained in
Reference numerals 1 and 45 denote memories connected to the external light reflection luminance estimation unit 40 and the leakage light luminance estimation unit 44, respectively.

FIG. 3 is an operation flowchart for explaining the operation of the control system of the image display device 30 including the controller 36 and the backlight control device 38 corresponding to the brightness of the ambient light. Hereinafter, a configuration of a control system of the image display device 30 according to the present embodiment and an operation corresponding to the brightness of ambient light in the image display device 30 will be described with reference to FIGS.

The external light monitor 34 detects the brightness of the external light (step 51 in FIG. 3). The brightness (monitor value) of the external light detected by the external light monitor 34 is sent to the external light reflection luminance estimating unit 40 of the controller 36. In step 52, the external light reflection luminance estimating unit 40 reads a relational expression, a table, and the like determined in advance from the memory 41, and uses the read relational expression, the table, and the like to read the brightness ( From the monitor value, the luminance b due to the reflection of the external light of the liquid crystal screen, that is, the luminance b due to the reflection of the liquid crystal screen corresponding to the ambient light state (brightness) detected by the external light monitor 34 is estimated. The relational expression between the external light monitor value and the brightness value b and the table used here are the external light monitor value detected from the external light monitor 34 and the external light reflection (backlight) of the liquid crystal screen at the time of the external light. 20 is off).
It is preferable to calculate from the relationship. The luminance value b estimated by the external light reflection luminance estimating unit 40 in this way is sent to the backlight adjustment signal generating unit 42.

On the other hand, the backlight monitor 32 detects the brightness of the backlight of the liquid crystal panel unit 10 (step 53 in FIG. 3). The brightness (monitor value) of the backlight 20 detected by the backlight monitor 32 is sent to the leak light luminance estimating unit 44 of the controller 36. from now on,
In step 54, a predetermined relational expression, a table, and the like are read out from the memory 45 by the leak light luminance estimating unit 44, and the brightness of the backlight sent from the backlight monitor (luminance monitor) 32 is used by using the relational expression and the table. From the (monitor value), the luminance a of the leakage light of the liquid crystal screen, that is, the luminance a of the leakage light of the liquid crystal screen determined by the luminance value of the backlight and the extinction ratio of the liquid crystal is estimated. The relational expression or table between the backlight monitor value and the luminance value a used here is obtained by comparing the backlight monitor value detected from the backlight monitor 32 and the minimum luminance value (leakage light) of the liquid crystal determined by the extinction ratio in advance. It is preferable to calculate from the relationship. The luminance value a estimated by the leakage light luminance estimating unit 44 in this way is sent to the backlight adjustment signal generating unit 42.

Next, at step 55, the backlight adjustment signal generator 42 compares the luminance a and the luminance b sent from the leakage light luminance estimator 44 and the external light reflection luminance estimator 40, respectively. That is, a ≦ n · b (n is 2 to
(Set within a range of 1 as appropriate) is checked.

In the check at step 55, a ≦ n
If it is determined that b holds, the backlight 2
It is not necessary to adjust the brightness of 0, and the backlight 20
What is necessary is just to maintain the state (setting state) as it is. Therefore, the backlight adjustment signal generator 42 does not generate a backlight adjustment signal for adjusting the brightness of the backlight 20 and does not send the backlight adjustment signal to the backlight controller 38. For this reason, the brightness of the backlight 20 is maintained at the set state by the backlight control device 38. On the other hand, in the check in step 55,
If it is determined that a ≦ n · b is not satisfied, the state (current setting state) is not preferable. Therefore, the backlight adjustment signal generation unit 42 adjusts the brightness of the backlight 20. A backlight adjustment signal for adjustment is generated and sent to the backlight control device 38. For this reason, the backlight control device 38 controls the backlight 20 according to the received backlight adjustment signal.
Is changed, that is, the backlight 20 is darkened (step 56), the process returns to step 53, and the above procedure shown in FIG. 3 is repeated.

That is, the backlight 20 changed to be darker
Is detected by the backlight monitor 32 (step 53), and the luminance a is calculated again by the leakage light luminance estimating unit 44 (step 54). Brightness estimator 4
The luminance a obtained in step 4 is compared with the luminance b previously obtained in the external light reflection luminance estimating unit 40 (it is checked whether a ≦ n · b is satisfied).

Here, if it is determined in the check in step 55 that a ≦ n · b is established, this state (set state) may be maintained. Also, in this case, a ≦
If n · b does not hold, the backlight 20 is further darkened, and steps 56 and 53 to 55 are repeated until a ≦ n · b holds.

According to the above embodiment, the brightness of the backlight 20 of the image display device can be controlled within a predetermined range with respect to the external light (environmental light) of the environment. (Doctor) can be displayed easily.

In the above embodiment, the backlight 2 of the liquid crystal panel unit 10 detected by the backlight monitor 32
When the brightness a of the leakage light of the liquid crystal screen determined by the brightness value of the backlight 20 and the extinction ratio of the liquid crystal is obtained from the brightness of 0, an example using a predetermined relational expression, table, or the like has been described. The present invention is not limited to this method.

For example, as shown in FIG. 4A, a graph showing the relationship between the (accumulated) use time of the backlight and the light emission luminance obtained in advance, and as shown in FIG. The current backlight brightness is estimated based on the contents of the graph showing the relationship between the light control signal and the light emission brightness, and is determined by this and the predetermined backlight brightness value and the extinction ratio of the liquid crystal. The aforementioned luminance a may be estimated from the relationship with the leak light.

In this case, instead of providing the backlight monitor 32 in the image display device 30 shown in FIGS. 1 and 2, the graphs shown in FIGS. Is stored in the memory 45 of the leakage light luminance estimating unit 44. Then, the leakage light luminance estimating unit 44 receives the (accumulated) use time of the backlight 20 and / or the backlight control signal from the backlight control device 38 or the backlight 20, and obtains a necessary graph relational expression from the memory 45. Alternatively, the current brightness (emission luminance value) of the backlight 20 may be obtained by reading a table or a table. At this time, the leakage light luminance estimating unit 44 uses the current brightness (light emission luminance value) of the backlight 20 obtained in this manner instead of the detection monitor value (brightness) of the backlight monitor 32, and Then, the luminance a of the leaked light (the minimum luminance of the liquid crystal) a of the liquid crystal screen is calculated from the emission luminance value of the liquid crystal and the extinction ratio of the liquid crystal.

Further, in the above embodiment, when the brightness b due to the reflection of the liquid crystal screen corresponding to this ambient light condition is obtained from the brightness of the outside light detected by the outside light monitor 34, a predetermined relationship is determined. Although an example using an expression, a table, and the like has been described, the present invention is not limited to this method. For example, similarly, from the brightness of the backlight 20 estimated above and the detection result of the ambient light brightness detection means, a brightness b due to reflection of the liquid crystal screen corresponding to a previously obtained brightness of the ambient light is obtained. This is also an effective method.

In the various embodiments described above, a ≦ n · b is set between the luminance a of the leakage light of the liquid crystal screen and the luminance b due to the reflection of the liquid crystal screen corresponding to the brightness of the ambient light.
When it is determined that (n is 2 to 1), the brightness of the backlight 20 is not adjusted and the backlight 20 is not adjusted.
Keeps the state (setting state) as it is, but the present invention is not limited to this, and the backlight 2
Since it is desirable that the luminance of 0 is as bright as possible, a ≦ a
The brightness of the backlight 20 may be adjusted by the controller 36 or the backlight control device 38 so that the brightness of the backlight 20 becomes 70% or more of the maximum brightness of the backlight 20 within a range where n · b is satisfied.

The above embodiments are merely examples of the present invention, and it is needless to say that the present invention is not limited to these embodiments.

[0035]

As described above, according to the present invention, in an image display device using a liquid crystal display device,
This has a remarkable effect that an image display device capable of making a display image truly easy to see regardless of the brightness of ambient light (ambient light) can be realized.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a schematic configuration of an embodiment of a control system of the image display device shown in FIG.

FIG. 3 is a flowchart illustrating an operation of the control system of the image display device illustrated in FIG. 1 corresponding to the brightness of ambient light.

FIG. 4A is a graph showing a relationship between backlight use time and light emission luminance obtained in advance, and FIG. 4B is a graph showing a relationship between a backlight control signal and light emission luminance.

[Explanation of symbols]

 Reference Signs List 10 liquid crystal display panel unit 12 liquid crystal display panel 20 backlight unit 30 image display device 32 backlight monitor 34 external light monitor 36 controller 38 backlight control device 40 external light reflection luminance estimation unit 41, 45 memory 42 backlight adjustment signal generation unit 44 Leakage Light Luminance Estimation Unit 51-56 Processing Step

Claims (5)

[Claims] 1. An image display device using a liquid crystal display device having a liquid crystal display device and a backlight, wherein the backlight of the liquid crystal display device is brightened when ambient light is bright, and the backlight is brightened when ambient light is dark. The backlight,
An image display device, comprising: a backlight control unit that darkens leakage light determined by an extinction ratio of a liquid crystal so as not to exceed a certain value. 2. The backlight control means includes: means for detecting the brightness of ambient light; and means for controlling the brightness of the backlight of the liquid crystal display device. The image display device according to claim 1, wherein brightness of the backlight is adjusted. Means for controlling the brightness of the backlight, means for detecting the brightness value of the backlight, and means for detecting the brightness value of the backlight and the extinction of the liquid crystal provided in the backlight. Means for estimating the brightness a of the leaked light from the liquid crystal screen from the relationship with the leaked light determined by the ratio, and based on the relationship between the brightness of the environmental light previously determined and the brightness b corresponding to the reflection of the liquid crystal screen. Means for obtaining, from the brightness of the ambient light detected by the means for detecting the brightness of the ambient light, a luminance b due to reflection of the liquid crystal screen corresponding to the brightness of the ambient light, The brightness is defined as the brightness a is the brightness b.
3. The image display device according to claim 2, wherein the image display device is controlled so as to be twice or less. 4. The means for controlling the brightness of the backlight, wherein the backlight determined in advance based on a relationship between a predetermined backlight luminance value and leakage light determined by an extinction ratio of the liquid crystal. Means for estimating the luminance a of the leakage light of the liquid crystal screen from the current backlight brightness estimated based on the relationship between the use time of the light and the light emission luminance and the relationship between the backlight control signal and the light emission luminance; From the brightness of the ambient light detected by the means for detecting the brightness of the ambient light, based on the relationship between the brightness of the ambient light previously determined and the brightness b due to the reflection of the liquid crystal screen corresponding thereto, Means for determining a brightness b due to reflection of the liquid crystal screen corresponding to the brightness of the ambient light, wherein the brightness a of the backlight is the brightness b
3. The image display device according to claim 2, wherein the image display device is controlled so as to be twice or less. 5. The image display device according to claim 3, wherein the control unit controls the brightness of the backlight so that the brightness a is equal to or less than the brightness b.