JPH0591376A - Display device - Google Patents

Abstract

PURPOSE:To obtain an optimum hue by driving an LCD at a color temperature in matching with an external light source based on an output of a white balance sensor when the external light source is selected. CONSTITUTION:An LCD drive circuit 4 does not fetch a white balance signal being an output of a white balance sensor 6 when a switch 7 is turned off. On the other hand, when a lever 23 (changeover knob 26) is thrown to the position to use an external light source, the switch 7 is turned on. The LCD drive circuit 4 fetches a white balance signal being an output of the white balance sensor 6 when the switch 7 is closed. In this case, the LCD drive circuit 4 matches a color temperature with an external light source radiating to an external light source radiating to the white balance sensor 6, that is, a light guide member 27 to drive an LCD 22. Thus, even when the lever 23 is thrown to the position of either the external light source or the internal light source, the LCD is driven at an optimum color temperature and monitored by an optimum hue.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device which can be switched between an internal light source and an external light source used in an LCD viewfinder such as a video camera.

[0002]

The present applicant has previously proposed a display device applied to a video camera as Japanese Patent Application No. 2-225960. This configuration is shown in FIG.

In FIG. 7, a subject image is formed on an image pickup element (CCD) 2 by a taking lens 1, and the image pickup element 2
Photoelectrically converted by. The video signal obtained by the image sensor 2 is
It is supplied to the video signal processing circuit 3. A white balance signal is supplied to the video signal processing circuit 3 from a white balance sensor 6 provided in the video camera.

The video signal processing circuit 3 adjusts the color temperature of the video signal obtained by the image pickup device 2 as a video signal for recording according to the white balance signal supplied from the white balance sensor 6 and outputs it to a recording circuit (not shown). To do. A part of the output of the video signal processing circuit 3 at this time is also supplied to the LCD drive circuit 5. The LCD drive circuit 5 uses the video signal supplied from the video signal processing circuit 3 to drive the LCD 2
Drive 2

The LCD 22 is illuminated with a backlight as will be described with reference to FIG. In FIG. 8A, reference numeral 21 denotes a housing, the LCD 22 is attached to the left end of the figure, and the LCD 2 is attached from the right end.
The display screen of No. 2 is observed. A lever 23 is rotatably supported laterally of the housing 21 with its center as a fulcrum, and switching shutters 24 and 25 are attached to upper and lower ends in the drawing. A switching knob 26 is operated to switch the switching shutters 24 and 25. Reference numeral 27 denotes a light guide member arranged behind the LCD 22. Reference numeral 28 denotes a light source (internal light source) including a lamp, a fluorescent lamp, and the like, and is arranged at the lower end portion of the light guide member 27 in the drawing.

In FIG. 8A, the switching knob 26 is switched to the internal light source. At this time, the switching shutter 24 closes the upper end of the light guide member 27 in the drawing, and the switching shutter 25 opens the lower end.

The light emitted from the light source 28 is guided by the light guide member 2.
7 is incident from the lower end thereof. The light guide member 27 guides the incident light to illuminate the rear surface of the LCD 22. A part of the light guided by the light guide member 27 reaches the upper end portion thereof, but the inner surface (lower side in the figure) of the switching shutter 24 is formed with a reflecting surface so as to reflect the light. Therefore, it is reflected by this reflecting surface and guided to the rear surface of the LCD 22. Therefore, the light is effectively used.

At this time, since the upper end of the switching shutter 24 is closed, the light from the external light source does not enter the light guide member 27.

Rotate the switching knob 26 clockwise in the drawing,
When switching to the external light source side, as shown in FIG.
The lever 23 rotates in the clockwise direction with its substantially center as a fulcrum. As a result, the upper switching shutter 24 moves to the right in the drawing, and the lower switching shutter 25 moves to the left,
The upper end of the light guide member 27 is opened and the lower end is closed.

The light emitted from the light source 28 is blocked by the switching shutter 25 and does not enter the light guide member 27.

On the other hand, since the upper end portion of the light guide member 27 is opened, the light from the external light source enters from there. The incident light is guided by the light guide member 27 and applied to the rear surface of the LCD 22. Further, a part of the light is reflected by a reflecting surface formed on the inner surface (upper side in the drawing) of the switching shutter 25, and L
The light is guided to the rear surface of the CD 22.

Therefore, in any case, since the light is emitted from the rear surface of the LCD 22, it becomes easy to see the image displayed on the LCD 22 from the right side in the figure.

[0013]

As described above, in the conventional display device, the LCD 22 is illuminated by the backlight. The external light source and the internal light source by the light source 28 are switched and used as the backlight. I am trying.

However, the hue of the LCD 22 depends on the light source 2.
It is set corresponding to the color temperatures of eight. Therefore, when an external light source such as sunlight is used, there is a problem in that the hue observed through the LCD panel changes due to the difference in color temperature.

The present invention has been made in view of the above problems, and an object thereof is to obtain an optimum hue regardless of whether an external light source or an internal light source is used as a backlight.

[0016]

In order to achieve this object, a display device of the present invention comprises an LCD for displaying a monitor image and a light source switching means for switching and supplying an internal light source and an external light source as a backlight of the LCD. In a display device having a white balance sensor that outputs a signal for white balance adjustment, and when the external light source is switched by the switching operation of the light source switching means, the color temperature adjusted to the external light source based on the output of the white balance sensor. And an LCD drive circuit for driving the LCD.

[0017]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a display device according to the present invention. In the figure, the same components as those in FIG. 7 or 8 are designated by the same reference numerals, and a duplicate description will be omitted.

In FIG. 1, the white balance sensor 6
The white balance signal, which is the output of, is supplied to the video signal processing circuit 3 and the LCD drive circuit 4. Switch 7
Are switched in conjunction with the lever 23 (switching knob 26). That is, the switch 7 is switched off when the lever 23 is switched to use the internal light source and is switched on when the lever 23 is switched to use the external light source.

When the lever 23 is switched to use the internal light source, the switch 7 is turned off. LC
When the switch 7 is off, the D drive circuit 4 does not take in the white balance signal output from the white balance sensor 6. At this time, the LCD drive circuit 4 drives the LCD 22 by adjusting the color temperature to the internal light source by the light source 28 as in the conventional case.

On the other hand, when the lever 23 is switched to use the external light source, the switch 7 is turned on. The LCD drive circuit 4 takes in the white balance signal output from the white balance sensor 6 when the switch 7 is in the ON state. At this time, the LCD drive circuit 4
An external light source that illuminates the white balance sensor 6,
Therefore, the LCD 22 is driven by adjusting the color temperature to the external light source with which the light guide member 27 is irradiated. As a result, regardless of whether the lever 23 switches between the external light source and the internal light source, the LCD 22 is driven at the optimum color temperature and can be monitored at the optimum hue.

Next, FIG. 1 will be described more specifically with reference to FIGS.

FIG. 2 is a block diagram showing an example of a concrete configuration of the main part of FIG.

In FIG. 2, an LCD drive circuit 4 is an analog / digital converter (hereinafter referred to as A / D converter) 4-1 and 4-2 for converting an analog signal into a digital signal.
A microcomputer 4-3, a ROM 4-4, and a digital / analog converter (hereinafter, referred to as a D / A converter) 4 for converting a digital signal into an analog signal.
5, 4-7, R gain controller 4-8, G gain controller 4-9, and B gain controller 4-10
And a gate driver 4-11 and a source driver 4-12. ROM4-4 contains R /
G, B / G tables are prepared, and this R / G, B
In the / G table, the values of R / G and B / G with respect to the color temperature and the gain control correction values ΔR /
G and ΔB / G are arranged.

Output of the white balance sensor 6 (R / G
Signal) is supplied to the microcomputer 4-3 via the A / D converter 4-1. The output of the white balance sensor 6 (B / G signal) is A /
The data is supplied to the microcomputer 4-3 via the D converter 4-2. The ROM 4-4 and the switch 7 are connected to the microcomputer 4-3.
The microcomputer 4-3 is connected to the source driver 4-12 via the D / A converter 4-5 and the R gain controller 4-8. The output end of the G gain controller 4-9 is connected to the source driver 4-12. The microcomputer 4-3 is connected to the source driver 4-12 via the D / A converter and the B gain controller 4-10. Also,
The R, G, and B signal outputs of the video signal processing circuit 3 are supplied to the R gain controller 4-8, the G gain controller 4-9, and the B gain controller 4-10, respectively.

Further, the video signal processing circuit 3 outputs the sync signal of the video signal to the gate driver 4-11. The LCD 22 is a TFT (thin film transistor) active matrix type LCD. The LCD 22 is provided with a TFT for each liquid crystal pixel. Gate driver 4-11, source driver 4-12
Turn on / off these TFTs to drive the LCD 22. Therefore, the gate driver 4
-11 outputs a scanning pulse as a gate pulse to the LCD 22 in response to the synchronizing signal of the video signal supplied from the video signal processing circuit 3. Then, in the LCD 22, when the scanning pulse comes, the corresponding TFT is turned on, the signal from the source driver 4-12 becomes effective, and the display corresponding to the video signal is performed.

Next, when the light source as the backlight of the LCD 22 is the internal light source 28, it is constant at about 8000 ° k, which varies depending on the individual LCD, and the hue of the LCD 22 is adjusted to this temperature. However, LCD2
When the light source as the backlight of 2 is switched to an external light source, it is about 5200 ° k outdoors during the day and about 700 when it is cloudy.
Since the color temperature is different such as 0 ° k, it is necessary to change the hue of the LCD 22 according to the output of the white balance sensor 6 according to the color temperature of the external light source.

Regarding the method of adjusting the hue of the LCD 22, the white balance sensor 6 of FIG. 3 and the LC of FIG.
This will be described using the D drive circuit 4.

First, as shown in FIG. 3, the white balance sensor 6 includes filters 6-1 to 6-3 for extracting R, G and B signals and logarithmic compression circuits 6-4 to 6-6, respectively.
And an integrated circuit (IC) including the arithmetic circuit 6-7.

In FIG. 3, the external light from the external light source is R,
R, G, and G through each of the G and B filters 6-1 to 6-3.
B is received and the values of the R, G, B signals are logarithmically compressed by the circuit 6-4.
Compress at 6-6. Then, the logarithmically compressed R,
The G and B signals are supplied to the arithmetic circuits 6-7, respectively, where they are arithmetically operated in the form of R / G and B / G. Arithmetic circuit 6-7
Supplies these R / G and B / G signals (voltage signals) to the microcomputer 4-3 via the A / D converters 4-1 and 4-2, respectively.

Here, the R, G, B signals are logarithmically compressed by the logarithmic compression circuits 6-4 to 6-6 because the brightness range is wide, and the ratio between the maximum value and the minimum value is several hundred times. Because it's big
This is to facilitate the processing. Further, in the case of the color temperature, the arithmetic circuit 6-7 converts the R / G signal and the B / G signal into not the absolute value of each R, G, B value but the relative value. Is. Further, the reason why G is used as a denominator like R / G and B / G is that G is the center of three sources among R, G, and B, and G is the reference. Further, for convenience of description, the white balance sensor 6 outputs the R / G signal and the B / G signal with the G signal as a reference, but the present invention is not limited to this, and the G / R is not limited thereto. Signal, B /
It is also possible to output the G signal (in practice, many output the G / R signal and the B / G signal as the white balance signal).

Output of the white balance sensor 6 (R / G
The characteristics of the signal and the B / G signal) are as shown in FIG. As can be seen from FIG. 4, for example, a color temperature of 8000
800 ° for 5000 ° and 5000 ° k
Compared to the case of 0 ° k, R / G is larger by ΔR / G and B / G is smaller by ΔB / G, so that it becomes reddish.

Therefore, the LCD drive circuit 4 performs a correction according to the output (R / G signal, B / G signal) from the white balance sensor 6 so as to increase the R component of the LCD 22 corresponding to ΔR / G. Then, the LCD 22 is driven. As a result, for example, even at 5000 ° k, 8000
It can be seen in the same hue as in the case of ° k.

The R component of the LCD 22 and ΔR / G are
Although there is a correlation (for example, a proportional relation or an inverse proportional relation), the correlation differs depending on each LCD. L
The same applies to the B component and ΔB / G of CD22.

The detailed operation of the LCD drive circuit 4 will be described with reference to the operation flowchart of FIG. Note that FIG. 5 is a flowchart of the operation of the microcomputer 4-3 in the LCD drive circuit 4.

The microcomputer 4-3 checks whether or not the switch 7 is in the ON state (step S
1) If the switch 7 is off, it is determined that the switching knob 26 of FIG. 1 is switched to the internal light source 28. And in this case, the microcomputer 4-3
The gain control correction values ΔR / G and ΔB / G are cleared, and the process proceeds to step S5 (step S2). In step S5, the microcomputer 4-3 clears the gain control correction values ΔR / G and ΔB / G, so that each of the R and B gain controllers 4-via the D / A converters 4-5 and 4-7. The gain control correction values ΔR / G and ΔB / G = 0 are output to 8 and 4-10.

Next, the microcomputer 4-3, if the switch 7 is in the off state, the A / D converters 4-1 and 4-2.
White balance sensor 6 A / D converted by
The R / G and B / G signals from are fetched (read) and stored in the built-in memory (steps S1 and S3). Next, the microcomputer 4-3 is written in the ROM 4-4. The gain control correction values ΔR / G and ΔB / G corresponding to R / G and B / G stored in the built-in memory are read from the R / G and B / G table,
This is taken in and R / from the white balance sensor 6
Gain control correction value ΔR / corresponding to G, B / G
G and ΔB / G are determined (step S4).

The microcomputer 4-3 transfers the gain control correction value ΔR / G to the R gain controller 4-8 via the D / A converter 4-5 and the gain control correction value ΔB / G to the D / A converter 4-. 7 to the B gain controller 4-10.

Next, the gains of the R, G, and B gain controllers 4, 8 to 4-10 are initialized to values corresponding to the color temperature of the internal light source 28, respectively. R
Gain controller 4-8, B gain controller 4-
Each gain in 10 is the D / A converter 4
Gain control correction values ΔR / G and ΔB / supplied from the microcomputer 4-3 via -5 and 4-7.
Depending on G, the initial value (value corresponding to the color temperature of the internal light source 28) is changed. However, the internal light source 2
When using 8, the gain controller 4 for each R and B
The gains of -8 and 4-10 are the initial values. In addition,
The gain in the G gain controller 4-9 is fixed.

R, G, B gain controllers 4-8
To 4-10 are R, G, and B from the video signal processing circuit 3.
The signal is multiplied by the gain to output the R ′, G ′, B ′ signals to the source driver 4-12.

The gate driver 4-11 corresponds to the synchronizing signal of the video signal supplied from the video signal processing circuit 3,
The scan pulse as the gate pulse is output to the gate bus of the LCD 22. In the LCD 22, when the scanning pulse comes, the TFT connected to the gate bus turns on,
The R ', G', and B'signals from the source driver 4-12 become valid, and the display corresponding to the video signal is performed.

As a result, on the LCD 22, the LCD 22
It is possible to always obtain an optimum hue not only when the internal light source 28 is used as the backlight of, but also when the external light source is used.

Next, each of the R, G, and B gain controllers 4-8 to 4-10 in FIG. 2 is constructed, for example, as shown in FIG. In FIG. 6, Q1 to Q5 are transistors, the transistor Q1 is used as an input buffer, and the transistor Q5 is used as an output buffer. C1 to C4 are capacitors, and R1 to R11 are resistors. + E is a reference power supply.

Here, the input from the video signal processing circuit 3 (R signal in case of R gain controller 4-8, G signal in case of G gain controller, B signal in case of B gain controller) is the capacitor C1, Transistor Q
1, and is supplied to the base of the transistor Q3 via the capacitor C2. On the other hand, at the base of the transistor Q4,
In the case of the R gain controller 4-8, the output voltage (ΔR / G signal voltage) from the D / A converter 4-5 is supplied, and in the case of the G gain controller 4-9, a predetermined voltage is supplied, and B In the case of the gain controller 4-10, the output voltage (ΔB / G signal voltage) from the D / A converter 4-10 is supplied.

The currents flowing through the collectors of the transistors Q2 and Q4 are I1 and I2, respectively, and the transistor Q3
If the current flowing through the collector of is I3, I3 = I1 +
There is a relationship of I2. Further, the voltage of the base of the transistor Q2 is constant. Therefore, if the voltage of the base of the transistor Q4 is increased, the relationship of I3 = I1 + I2 is established, so that I1 decreases, I2 increases, and the gain can be increased. The transistors Q2 and Q4 function as a kind of differential amplifier.

Then, R from the video signal processing circuit 3
Each of the G and B signals is amplified and supplied to the base of the transistor Q5 via the capacitor C4 and the transistor Q5.
The output (each signal of R ', G', B ') is taken out from the collector of.

Although the white balance sensor provided in the video camera is used as the white balance sensor 6 in the present embodiment, the present invention is not limited to this, and the white balance sensor is provided in the video camera. It goes without saying that a white balance sensor may be newly provided instead of using the existing white balance sensor.

The present invention is not limited to this embodiment,
Various applications and modifications are conceivable without departing from the scope of the present invention.

[0049]

As described above, according to the display device of the present invention, when the LCD drive circuit is switched to the external light source by the switching operation of the light source switching means, the LCD drive circuit is switched to the external light source based on the output of the white balance sensor. Since the LCD is driven at the combined color temperature, even when an external light source is used as the backlight instead of the internal light source, the LC
On D, the optimum hue can always be obtained.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a display device according to the present invention.

FIG. 2 is a block diagram showing a specific configuration example of a main part of FIG.

FIG. 3 is a block diagram showing a specific example of the white balance sensor 6 of FIG.

FIG. 4 is a diagram showing an output characteristic of the white balance sensor 6 of FIG.

5 is a flowchart of the operation of a microcomputer 4-3 in the LCD drive circuit 4 of FIG.

6 is a circuit diagram showing an embodiment of each R, G, B gain controller in the LCD drive circuit 4 of FIG.

FIG. 7 is a side view showing an example of a conventional display device.

FIG. 8 is a side view for explaining the operation of the main parts of FIG.

[Explanation of symbols]

 1 Photographing lens 2 Image sensor 3 Video signal processing circuit 4 LCD drive circuit 6 White balance sensor 7 Switch 21 Housing 22 LCD 23 Lever 24, 25 Switching shutter 26 Switching knob 27 Light guide member 28 Internal light source

Claims (1)

[Claims] 1. A white balance sensor for outputting a signal for white balance adjustment in a display device having an LCD for displaying a monitor image and a light source switching means for switching and supplying an internal light source and an external light source as a backlight of the LCD. And an LCD drive circuit that drives the LCD at a color temperature matched to the external light source based on the output of the white balance sensor when the external light source is switched by the switching operation of the light source switching means. Characterized display device.