JPS63261327A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent automatically a color LCD screen from varying in hue and color tone owing to variation in the color temperature of light by correcting the hue of a display signal corresponding to color temperature detected by a sensor which detects the color temperature of light from an internal or external light source. CONSTITUTION:The color temperature of back light to a color LCD (liquid crystal display body) 5 is detected by the sensor 6 as, for example, the ratio of the quantities of transmitted light of three primary colors and outputted as a detection signal to a control circuit. The control circuit, on the other hand, outputs a correcting signal for controlling the relative level of the three primary color driving signal of the color LCD 5 so that when the back light is used, the white balance of the LCD screen 14 is adjusted according to the detection signal from the sensor 6. Consequently, the influence of the color temperature of the back light on the color LCD 5 is eliminated and the white balance is adjusted, so that an image having an excellent hue which is reproduced faithfully is displayed on the screen 14 of the color LCD 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color liquid crystal display device, and particularly to a color liquid crystal display device using a transmissive color liquid crystal display (hereinafter referred to as a color LCD).

[Summary of the invention]

This invention includes a sensor that detects the color temperature of light from an internal light source or an external light source that can be selectively used, and a control circuit that corrects the hue of a display signal in accordance with the color temperature detected by the sensor. This automatically prevents the hues of the color LCD screen from changing due to changes in the color temperature of the light irradiated from the light source to the color LCD screen. are doing.

[Conventional technology]

Conventionally, transmissive liquid crystal displays (hereinafter referred to as LCDs), including color LCDs, have required backlight irradiation from the back side of the LCD, and the light sources for this backlight include natural light and fluorescent lamps. , incandescent lamps, etc. are mainly used.

Each of these light sources has a unique color temperature, and when the light source of the bank light changes, the color temperature of the bank light changes, and the color tone of the LCD screen may change accordingly.

On the other hand, even if the light source does not change, such as when the internal light source built into the device is Buffklight, the color temperature will change over time due to changes in lamps, fluorescent tubes, etc.

It changes due to variations in specifications, variations during manufacturing, changes in power supply voltage, etc., and is difficult to keep constant.

The light (backlight) obtained from the light source has a different color temperature (i.e., color tone) depending on the type of light source, and even if the same light source is used, depending on the usage conditions. The change in color temperature of LC
This destroys the white balance of the D screen, and as a result, the original color tone of the image obtained from the color video signal may not be faithfully reproduced.

To solve this problem, conventional color liquid crystal display devices include
A HUE volume was provided for white balance adjustment. By manually operating the HUE volume to adjust the white balance, the influence of changes in the color temperature of the backlight on the color tone of the LCD screen (image) can be eliminated.

[Problem that the invention seeks to solve]

However, in such conventional color liquid crystal display devices, adjusting the HUE volume is quite troublesome, and the color tone of the image displayed on the LCD is adjusted by adjusting the white balance in response to changes in the color temperature of the backlight. In practice, it is very troublesome, time-consuming, and difficult to faithfully reproduce and stably maintain a system, so improvements have been desired.

Furthermore, when the cabinet is small, it is difficult to secure a space for the HUE volume and its associated circuits, and improvements have been desired in this respect as well.

Therefore, it is an object of the present invention to provide a color liquid crystal display device that can automatically eliminate the influence on the color tone of the color LCD screen (image) even if the color temperature of the buffcrite irradiated onto the color LCD changes. It is about providing.

[Means for solving problems]

In this invention, in a color liquid crystal display device that irradiates light from either an internal light source or an external light source that can be used selectively to a liquid crystal display body that displays an image, the internal light source or the external light source is used. The device is equipped with a sensor that detects the color temperature of light from the sensor, and a control circuit that corrects the hue of the display signal in accordance with the color temperature detected by the sensor.

[Effect]

The color temperature of a backlight for a color LCD is detected by a sensor, for example, as a ratio of the amount of light transmitted through each of the three primary color filters, and this is output as a detection signal to a control circuit. On the other hand, the control circuit controls the color LCD so that the white balance of the LCD screen is adjusted based on the detection signal from the sensor when the above-mentioned backlight is used.
A correction signal is output for controlling the relative levels of the three primary color drive signals. As a result, the influence of the color temperature of the backlight on the color LCD is automatically eliminated, the white balance is adjusted, and a faithfully reproduced image with good color tone can be displayed on the screen of the color LCD.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a color liquid crystal display device using a transmissive color LCD as a display element as shown in FIGS. 1 to 3.

This color liquid crystal display device mainly includes a tuner 1, a video detection circuit 2, an HLJE volume 3, a signal processing circuit 4, a color LCD 5, a sensor 6, a control signal generation circuit 7, and a fluorescent lamp 8. configured.

The tuner 1 extracts the signal component of the channel to be selected from the television signals S and V received by the antenna 9, amplifies it, and converts it into a color video signal SCP and an audio signal. The video detection circuit 2 amplifies and detects the color video signal SCP obtained from the tuner 1, extracts combo shift signals SCO, 4, and then outputs them to the signal processing circuit 4 at the next stage.

The HUE volume 3 applies a bias to the correction signal SEEL outputted from the control signal generation circuit 7 and outputs it to the signal processing circuit 4, and is manually operated as in the conventional case.

The signal processing circuit 4 receives the composite signal S eOM and applies a drive voltage to the row electrodes X and column electrodes Y of the color LCD 5 in synchronization with the horizontal synchronization signal and vertical synchronization signal included in the composite signal S COM, thereby controlling the row and column electrodes. column electrode X,
By driving the pixel Ei formed at the intersection of Y, the image P!
, is displayed. Furthermore, this signal processing circuit 4 performs processing such as YC separation single-color demodulation and matrix calculation based on the composite signal SC0M to produce red (R), green (G),
The primary color signals R-G-B of blue (B) are separated, and the voltages V, , V6, ■ as display signals are formed corresponding to each level of each of these primary color signals R-G-B. 3, the correction signal S vcoe after applying the above bias (hereinafter,
Bias correction signal) is converted into three primary color drive signals, that is, voltages V, C, and V. C+ None with VcC, color LCD
5.

The color LCD 5 is attached to a color LCD fixing frame 12 which is rotatable to the cabinet 11 at an intersection 10. The color LCD 5 displays an image P1° by applying a driving voltage to the row electrodes X and column electrodes Y arranged in a matrix therein to drive the pixels EiJ. And, this color LCD 5 has the back 13
It is a transmissive type that enhances the contrast of the screen 14 by irradiating the Buffklight BL from the side and makes the displayed image PtcL visible. This color LCD
Each pixel E4J of 5 has a voltage V* as a display signal,
Vc and Vm are the three primary color drive signals, that is, the voltages VIC+ and VGC+, according to the bias correction signal svco*.
It is converted into V■ and applied. And this voltage lc
+ VGC + Each pixel E depending on the level of VIc
The hue, saturation, and brightness when driving ij are determined.

Note that this color LCD 5 is set so that the white balance matches the case where a fluorescent lamp 8 as an internal light source is used as a backlight BL as a reference. This standard bank light is expressed as SEL.

The sensor 6 is attached to the back surface 15 of the color LCD fixing frame 12 within the irradiation range 16 of the backlight BL in order to detect the color temperature of the backlight BL. This sensor 6 detects the backlight BLO color temperature as a ratio of the amount of transmitted light of each of the three primary color filters, and outputs this to the control signal circuit 7 as a detection signal S BET.

The control signal ordering circuit 7 receives the detection signal 3112 from the sensor 6? Therefore, 3 included in the backlight BL
The primary color component ratio R3 of the primary color signal R-G-B (i.e., R:G
: Obtain B). On the other hand, the control signal generation circuit 7
With respect to the reference backlight SBL, a relative primary color component ratio R0 with respect to the green (G) primary color component is set. When based on the relative primary color component ratio R++t1 of this reference butterfly) SBL, color LCD5
The white balance of the screen 14 can be adjusted satisfactorily.

The detection signal of the sensor 6 is S Ill! ? The primary color component ratio R8 of the backlight BL obtained from is corrected based on the green (G) primary color component, and the primary color component ratio (Rs, ++tLA)
is formed. This primary color component ratio Rs,□ is compared with the relative primary color component ratio R□LA of the reference backlight SBL, and a difference in the relative level is detected. A correction signal S is generated by the control signal generation circuit 7 to correct this difference. , is held in the control signal generation circuit 7 and the HUE volume 3
The signal is output to the signal processing circuit 4 after being subjected to bias adjustment. That is, the correction signal S,. 1 is Battarai) BL's relative primary color component ratio Rs, □, is the reference Battarai! -5BL's relative primary color component ratio R It is formed by such coefficients.

The fluorescent lamp 8 is used as an internal light source, and is installed in a light source storage section 17 in the cabinet 11, and is automatically turned on when the color LCD fixing frame 12 is fixed to the cabinet 11.

Note that 18 is a diffuser plate for making the illuminance distribution of the light from the fluorescent lamp 8 uniform, and 19 is a guide.

Next, in this color liquid crystal display device, backlight B
The operation when the LO color portion changes will be explained.

The image Pic of the selected channel is in color t.

In the normal operating state shown in CD5, the color LCD fixing frame 12 is moved in the opening direction (arrow 0 direction) and the fluorescent lamp 8 is turned off to change the light source of the bank light BL from the fluorescent lamp 8. When switching to natural light as an external light source, the backlight BLO chromaticity is detected by the sensor 6 as a ratio of the amount of light transmitted through the three primary color filters.

The color temperature of this natural light (backlight BL) is output from the sensor 6 to the codontrol signal generation circuit 7 as a detection signal SBL. In the control signal generation circuit 7, based on the detection signal S DllT, the backlight BL
The primary color component ratio R8 of red (R), green (G), and blue (B) is converted into a relative primary color component ratio Rl*tLA with respect to the green (G) primary color component. In the control signal generation circuit 7, the detection signal SDE? The control signal generation circuit 7 calculates the relative primary color component ratio R3, □ obtained from
Reference backlight set in advance) SBL relative primary color component ratio R11! Compare against. Then, for each primary color component, the primary color component ratio Rs of BL,
*ztA is the primary color component ratio R□ of the reference backlight SBL
, and the correction signal scow formed from this is biased by the HUE volume 3 to obtain the correction coefficient 11Li (bias correction signal 5VC0).
, ) is output to the signal processing circuit 4.

This correction signal S,. Eh, the HUE volume 3 is used for fine adjustment of the white balance on the screen 14 of the color LCD 5, and by manually operating the HUE volume 3,
Correction signal S,. A bias correction signal svcoi with a bias applied thereto is formed.

This bias correction signal S vcoi is supplied to the signal processing circuit 4
The level of each voltage V, , V, , V, which is applied to the primary color signal R-G-B and is formed based on the primary color signal R-G-B, is adjusted to the voltage Vmc+Vcc+VIC according to the bias correction signal Svco++.
The image is converted into a color image and applied to the color LCD 5 to obtain white balance under natural light.

In addition, if you switch from using natural light (external light source) to fluorescent light 8 (internal light source) as Bafuku Light BL, the Bafuku Light BL obtained from sensor 6)
Relative primary color component ratio Rs of BL.

IEL^ is compared with the relative primary color component ratio R□ at the time of the reference backlight SEL.

In this case, since the fluorescent lamp 8 is used as the backlight BL, the primary color component ratio R31! obtained and converted from the detection signal Snw! LA is the same as the primary color component ratio R■LA of the reference backlight SBL. Therefore, the relative primary color component ratio RIELA of the reference backlight SBL is output as is as the correction signal SCO, and is replaced with the conventional data and retained, and the white balance of the screen 14 of the color LCD 5 is Adjustments are being made. In addition, if the color temperature of the backlight BL changes due to the specifications of the fluorescent lamp 8, variations during manufacturing, changes over time, etc., the detection signal SI, ! Primary color component ratio R obtained from
Since s, □, changes, a difference will occur from the primary color component ratio R□LA of the reference bank (cry) SBL, and in order to maintain the white balance, the above-mentioned correction signal 5colI is used.
(bias correction signal 5VC0,) is output and the corresponding voltage value VIIC+Vl+C+vsc is color L
It will be applied to CD5, and the white balance will be adjusted.

As a result, when the type of light source of the bank light BL changes, or when the color temperature of the back light BL changes even if the light source of the back light BL does not change, the screen 14 of the color LCD 5 always automatically changes. Bank Cry) BL
White balance adjustment is performed according to the color temperature. As a result, a change in the backlight 1-BLO color portion can be prevented from affecting the color tone of the screen 14 (image P!cz) of the color LCD 5. In addition, in this embodiment, an example in which HUE volume 3 is provided is explained, but
The example is not limited to this, and the HUE volume 3 may be omitted, and the light from the fluorescent lamp 8 is used as the reference bank light SBL, and the white balance is adjusted using this. However, the present invention is not limited to this. The selection of the light source for the reference backlight SBL is arbitrary.

〔Effect of the invention〕

This invention includes a sensor that detects the color temperature of light from an internal light source or an external light source that can be selectively used, and a control circuit that corrects the hue of a display signal in accordance with the color temperature detected by the sensor. Even if the color temperature of the light irradiated from the light source to the color LCD changes,
A color LCD screen has the advantage that the white balance is always maintained and the color tone of the image is faithfully reproduced.Also, since the adjustment and maintenance of this white balance is performed automatically, there is no need for the troublesome HUE balance as in the past. This has the effect that no adjustment is required at all. Furthermore, since the HUE balance volume and its associated circuits are no longer necessary, there is also the additional effect of freeing up space within the cabinet.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a color liquid crystal display device to which the present invention is applied, FIG. 2 is a partially enlarged view of main parts showing a color LCD and a fluorescent lamp, and FIG. 2 is a block diagram of the color liquid crystal display device shown in FIG. 1. FIG. Explanation of main symbols in the drawings 4: Signal processing circuit, 5: Color LCD, 6: Sensor, 7: Control signal generation circuit, 8: Fluorescent lamp,
Ptct: Image.

Claims (1)

[Claims] In a color liquid crystal display device that irradiates a liquid crystal display for displaying an image with light from either an internal light source or an external light source that can be used selectively, the internal light source Alternatively, a color liquid crystal display device comprising: a sensor that detects the color temperature of light from an external light source; and a control circuit that corrects the hue of a display signal in accordance with the color temperature detected by the sensor.