JPH042544Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal color display device for displaying color images.

[Summary of the idea]

This invention relates to a liquid crystal color display device.
By controlling the input signal level according to the spectral characteristics of the light source, it is possible to always obtain the correct white balance no matter what kind of light source is used.

[Conventional technology]

For example, it has been proposed to display color images using liquid crystals.

In Fig. 3, 1 is an input terminal to which an image signal is supplied, and the signal from this input terminal 1 is transmitted in _the vertical (Y-axis) direction through switching elements M ₁ , M ₂ . are supplied to the lines L ₁ , L ₂ . . . L _n . Note that m is a number corresponding to the number of pixels in the horizontal (X-axis) direction.
Further, an m-stage shift register 2 is provided, and clock signals Φ _1H and Φ 2H of m times the horizontal frequency are supplied to this shift register 2, and clock signals Φ _1H and Φ _2H from each output terminal of this shift register _{2 are} supplied. Drive pulse signals φ _H1 , φ _H2 ... sequentially scanned by
...φ _Hn is supplied to each control terminal of the switching elements M ₁ to _{M n} . Note that shift register 2 has a low potential.
V _SS and a high potential V _DD are supplied, and drive pulses of these two potentials are formed.

In addition, switching elements M ₁₁ and M ₂₁ each consisting of, for example, an N-channel FET are connected to each line L ₁ to L _n .
...M _o1 , M ₁₂ , M ₂₂ ... M _o2 , ... M _1n , M _2n ,
One end of M _on is connected. Note that n is a number corresponding to the number of horizontal scanning lines. This switching element M ₁₁
~The other ends of M _on are respectively liquid crystal cells C ₁₁ and C ₂₁ ……
Connected to target terminal 3 through C _on .

Further, an n-stage shift register 4 is provided, and horizontal frequency clock signals Φ _{1V and Φ 2V are} supplied to this shift register 4. Drive pulse signals φ _V1 , φ _V2 that are sequentially scanned...
φ _Vo is the gate line G ₁ , G ₂ in the horizontal (X-axis) direction...
Through G _o , the switching elements M ₁₁ to _{M on} are supplied to control terminals for each row M ₁₁ to _{M 1n} , M ₂₁ to M _2n . . . M _o1 to _{M on} in the X-axis direction. Note that shift register 4 also has V _SS in the same way as shift register 2.
and V _DD are supplied.

That is, in this circuit, shift registers 2 and 4 are supplied with clock signals Φ _1H , Φ _2H , Φ _1V , and Φ _2V as shown in FIGS. 4A and 4B. The shift register 2 outputs φ _H1 to φ _Hn for each pixel period as shown in C in the same figure, and the shift register 4 outputs φ _V1 to φ _Vo in each horizontal period as shown in D in the same figure. Output.

When φ _V1 and φ _H1 are output, switching elements M ₁ and M ₁₁ to _{M 1n} are turned on, and input terminal 1 → M ₁ → L ₁ → M ₁₁ → C ₁₁ → target terminal 3
A current path is formed to input terminal 1 to liquid crystal cell _C11.
The potential difference between the signal supplied to the target terminal 3 and the target terminal 3 is supplied. Therefore, for the capacity of this cell C ₁₁ ,
A charge corresponding to the potential difference due to the signal of the first pixel is sampled and held. The light transmittance of the liquid crystal changes depending on the amount of charge. The same thing is done sequentially for cells C ₁₂ to _{C on} , and when the next field signal is supplied, each cell
The amount of charge of C ₁₁ to _{C on} is rewritten.

In this way, the light transmittance of the liquid crystal cells C ₁₁ to C _on is changed corresponding to each pixel of the video signal, and this is sequentially repeated to display the pixels.

Furthermore, in the above-mentioned device, the display can be colored by arranging a color filter of a predetermined color for each liquid crystal cell C and making the video signal supplied to the input terminal 1 a corresponding color signal. can.

That is, color filters (R=red, G=green, B=
For example, as shown by the dashed-dotted line in the figure, the blue) is extended vertically and sequentially repeated in the horizontal direction. And for the color filters arranged like this,
For example, the color signals of three colors are clocked using the clock signals Φ _1H and Φ _2H.
A color image can be displayed by switching sequentially in synchronization with the input terminal 1 and supplying the signal to the input terminal 1 so as to match the color filter arranged in the liquid crystal cell to which the signal is supplied.

However, in such a liquid crystal display device, display is performed by reflecting or transmitting external light or light from an internal light source. Therefore, the color reproduction of the display is affected by the spectral characteristics of this light source, and it is necessary to adjust the transmission characteristics of the color filter and the level, amplitude, etc. of each color signal to be supplied in accordance with the light source used.

However, since the above-mentioned liquid crystal display device can be made small and lightweight, there is a high possibility that the device will be taken outdoors for use. In that case, for example, if the above adjustment has been made assuming a light source such as an indoor electric light for a device that does not have an internal light source, when the device is taken outdoors and sunlight is used as the light source, the electric light and sunlight Due to the difference in spectral characteristics with light, color reproduction was not performed correctly.

Further, even in devices having an internal light source, the spectral characteristics of the internal light source may change due to aging or a drop in power supply voltage, and in this case as well, color reproduction becomes incorrect.

By the way, in a black and white liquid crystal display device, it has been proposed to adjust the display brightness according to the amount of external light (Japanese Patent Application No. 77793/1983).

That is, this device detects the amount of external light, and depending on this amount, for example, when the external light is strong, the brightness is lowered, and when the external light is weak, the brightness is increased.

However, this device only adjusts the brightness according to the amount of external light in a black-and-white liquid crystal display device, and does not respond to changes in the spectral characteristics of the light source in a liquid crystal color display device.

[Problem that the invention attempts to solve]

Conventional devices were constructed as described above. For this reason, the conventional apparatus has had the problem that color reproduction of the display cannot be performed correctly due to changes in the spectral characteristics of the light source.

[Means for solving problems]

The present invention has a plurality of first signal lines L ₁ , L ₂ . . . L _n provided in parallel in the vertical direction, and a plurality of second signal lines G ₁ , G ₂ provided in parallel in the horizontal direction. ... _Go
are provided, and display liquid crystal cells C ₁₁ , C ₁₂ ...C _on are provided at each intersection of these first and second signal lines via selection elements M ₁₁ , M ₁₂ ...M _on , respectively. In addition, in the liquid crystal color display device, color filters RGB are provided in a predetermined arrangement with respect to the liquid crystal cell, and respective color signals are supplied to the liquid crystal cell according to each of the color filters. Light receiving elements 7R, 7 that detect the spectral characteristics of the incident light entering the color filter
7B, and the proportion of the color signal is controlled (gain control amplifiers 5R, 5G, 5B) according to the detection output from the light receiving element. .

[Effect]

According to this device, the spectral characteristics of a light source are detected,
Since the input signal level is controlled accordingly, a good white balance can always be obtained even if the light source changes.

〔Example〕

In FIG. 1, red, green, and blue color signals from input terminals 1R, 1G, and 1B are supplied to each contact of a switch 6 through gain control amplifiers 5R, 5G, and 5B, respectively, and this switch 6 receives a clock signal Φ _1H.
and Φ _2H , and the signal from this switch 6 is supplied to switching elements M ₁ to _{M n} .

In addition, in relation to the color filter RGB, the light receiving element 7R,
7G and 7B are provided.

Here, a cross-sectional view of the liquid crystal display device is shown in FIG. 2. For example, a glass substrate 21
Switching elements M ₁₁ , M _{12 .} . . are formed on the substrate 21 and a liquid crystal 2
3 are sealed, and the liquid crystal cells C ₁₁ , C ₁₂ . . .
is formed. Note that color filters RGB are provided inside the counter electrode 22. Further, deflection plates 24 and 25 are provided outside the substrate 21 and the counter electrode 22.

Furthermore, a switching element is provided on the substrate 21.
The light receiving elements 7R, 7 are formed in the same process as M ₁₁ ~ M _on .
G, 7B is formed. Note that 26 is a transparent protective layer.

Signals from the light receiving elements 7R, 7G, 7B are supplied to gate elements 8R, 8G, 8B, and a pulse signal φ _CK is supplied to these gate elements from the gate terminal 9 at an arbitrary timing. Signals from these gate elements 8R to 8B are sent to the preamplifier 10, respectively.
It is supplied to R, 10G, and 10B. Incidentally, signals from the human control units 11R, 11G, and 11B are also supplied to the amplifiers 10R to 10B. Then, the signals from these amplifiers 10R to 10B are transmitted to integration circuits 12R, 12G, and 12B, respectively.
The signal is supplied to the gain control elements of the gain control amplifiers 5R to 5B.

Therefore, according to this device, external light is filtered through a color filter.
The light intensity levels (characteristics) of each of the RGB spectra are detected by the light receiving elements 7R to 7B, and depending on the spectral characteristics, for example, when red is strong and blue is weak, the gain control amplifiers 5R to 5B lower the gain of red. , control can be performed to increase the blue gain. This allows you to always obtain accurate white balance.

Note that in the above-described device, the timing of the pulse signal _φCK may be performed periodically, for example, for each vertical synchronization signal, or may be irregular.

Further, according to the above-described device, it is possible to correct not only changes in the light source but also changes in the transmission characteristics due to aging of the liquid crystal 23 and the like.

Further, in the case of a device having an internal light source, the light receiving elements 7R to 7B are provided outside the color filter, and the surrounding area is shielded from light to detect the spectral characteristics of the light from the internal light source that has passed through the liquid crystal 23 or the like.

This device is also effective when used in combination with the circuits in the above-mentioned references.

Furthermore, this device can be applied to the case where the switching elements M ₁ to _{M n} are divided into three systems according to the color combinations of the connected liquid crystal cells, and color signals are supplied to each system independently. In that case, the switch 6 is unnecessary. become. It can also be applied to other signal input formats.

[Effect of idea]

According to the present invention, the spectral characteristics of the light source are detected and the input signal level is controlled accordingly, making it possible to always obtain a good white balance even when the light source changes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 and 4 are diagrams for explaining a conventional device. L ₁ to _{L n} are vertical signal lines, G ₁ to _{G o} are gate lines, M ₁₁ to _{M on} are switching elements, C ₁₁ to _{C on} are liquid crystal cells, R is a red color filter, and G is a green color filter. , B is a blue color filter, 1R, 1G, 1B are input terminals, 5R, 5G, 5B are gain control amplifiers,
7R, 7G, and 7B are light receiving elements.

Claims (1)

[Claims for Utility Model Registration] A plurality of first signal lines provided in parallel in the vertical direction and a plurality of second signal lines provided in parallel in the horizontal direction are provided, and these first, A display liquid crystal cell is provided at each intersection of the second signal line via a selection element, and a color filter is provided in a predetermined arrangement corresponding to the liquid crystal cell. A liquid crystal color display device in which a color signal of is supplied to the liquid crystal cell is provided with a light receiving element for detecting the spectral characteristics of the incident light incident on the liquid crystal cell and the color filter, and a detection output from the light receiving element is A liquid crystal color display device characterized in that the proportion of the color signal is controlled accordingly.