JPH05289056A - Liquid crystal display density controller - Google Patents

Abstract

PURPOSE:To always adjust segment density of a liquid crystal element to an optimal state by controlling automatically a set voltage value at the time of driving a liquid crystal display element in accordance with the segment density in a turn-on state and the segment density in a turn-off state. CONSTITUTION:On a liquid crystal material 9 side of rear face glass 8, an electrode 10 for forming a segment of an information display part 5b and an electrode 11 for forming density detection segments Sd, Sc are arranged. In the upper part of these density detection segments Sd, Sc, a pair of light emission diodes 12, 13 (LED) are arranged, and in the lower part, a pair of phototransistors 14, 15 (PTR) are arranged. In such a state, light from LEDs 12, 13 passes through the density detection segments Sd, Sc, and thereafter, is made incident on the PTRs 14, 15, by which density of the density detection segments Sd, Sc is detected. Accordingly, in accordance with segment density in a turn-on state and segment density in a turn-off state, a set voltage value at the time of driving a liquid crystal display element 5 can be adjusted automatically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for displaying various kinds of information, and more particularly to a liquid crystal display density control device capable of controlling the display density of a liquid crystal display element to an optimum state.

[0002]

2. Description of the Related Art Recently, for example, in a camera, a display device using a liquid crystal display element is widely used to display photographing information such as a shutter speed, an aperture value, an exposure mode of the camera.

In such a liquid crystal display device, for example, unlike a light emitting diode, the liquid crystal display element does not emit light directly, so that there is an advantage that the current consumption is small and a wide variety of displays can be performed with a small number of electrodes. is there.

On the other hand, in a liquid crystal display device, the segment density of the liquid crystal display element generally changes due to a change in temperature. Especially, when a multiplexing driving method is adopted, the segment of the liquid crystal display element to be turned off becomes dark at high temperature. On the contrary, at low temperature, the segment to be lit looks thin at low temperature, and it is difficult to always maintain the display density in the optimum state.

Therefore, conventionally, there is known a liquid crystal display device in which a dial for adjusting the density is provided so that the user can adjust the display density each time the user uses it.

[0006]

However, in such a conventional liquid crystal display device, since a dial for adjusting the density is required, for example, a device such as a camera in which the space for installing the dial is limited. Then, it is difficult to set the dial in a size that is easy to adjust and to install the dial in a position that is easy to adjust.

Moreover, even if the dial can be installed,
The user himself / herself needs to adjust the display density each time he / she is used, which may cause an important photo opportunity to be missed. It is known that a temperature sensitive element such as a thermistor is provided in the drive section of the liquid crystal display element to prevent the segment density of the liquid crystal display element from changing due to a change in temperature, and the drive voltage is automatically adjusted. However, this method has a problem that the density cannot be adjusted sufficiently.

The present invention has been made in order to solve such a conventional problem, and an object thereof is to provide a liquid crystal display density control device capable of always adjusting the segment density of a liquid crystal display element to an optimum state. To do.

[0009]

A liquid crystal display density control device according to the present invention comprises a liquid crystal display element, a driving means for driving the liquid crystal display element at a set voltage value, and a segment in a lighting state of the liquid crystal display element. Detection means for detecting a density difference between the density and the density of the segment in the extinguished state, and the driving means drives the liquid crystal display element in accordance with the segment density in the illuminated state and the segment density in the extinguished state detected by the detection means. And a control means for changing the set voltage value at the time.

[0010]

In the liquid crystal display density control device of the present invention, the set voltage value for driving the liquid crystal display element is set to the optimum segment density according to the segment density in the lighted state and the segment density in the unlit state. Is automatically changed to.

[0011]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a camera equipped with an embodiment of a liquid crystal display density control device of the present invention. A camera lens 1 is attached to a camera body 1, and a subject image can be viewed through a finder 3. Has been done.

Further, the camera body 1 is provided with a release button 4, and when the release button 4 is pressed, the film is exposed. Further, a liquid crystal display device 5 (hereinafter referred to as LCD) is arranged in the camera body 1, and various display information can be visually recognized on the display unit 6.

FIG. 2 shows the details of the LCD 5. A liquid crystal display element portion 5a of the LCD 5 is provided with a rectangular information display portion 5b surrounded by a broken line.
In b, shooting information such as shutter speed and aperture value is displayed.

The information display section 5b corresponds to the display section 6 shown in FIG. 1 and is an area visible from the outside. A pair of density detection segments Sd and Sc are provided in a region below the information display unit 5a of the liquid crystal display element unit 5a, that is, a region invisible from the outside.

As will be described later, the density detecting segment Sd is constantly turned on, and the density detecting segment Sc is
Is always off. An external electrode 5c for applying a drive voltage is provided outside the liquid crystal display element section 5a.

FIG. 3 is a cross-sectional view of FIG. 2, in which a front glass 7 and a rear glass 8 are arranged to face each other with a predetermined gap, and a liquid crystal material 9 is enclosed between these glasses 7, 8. ing.

On the liquid crystal material 9 side of the rear glass 8, an electrode 10 forming a segment of the information display portion 5b and an electrode 1 forming a concentration detecting segment Sd, Sc.
1 is arranged.

These electrodes 10 and 11 are connected to the above-mentioned external electrode 5c, respectively. FIG. 4 shows the details of the detecting means for detecting the densities of the density detecting segments Sd, Sc. Above the density detecting segments Sd, Sc, a pair of light emitting diodes 12, 13 (hereinafter referred to as LED
, And a pair of phototransistors 14 and 15 (hereinafter referred to as PTR) are arranged below.

The light from the LEDs 12 and 13 passes through the density detecting segments Sd and Sc, and then the PTR1.
The light enters the light beams 4 and 15, and the densities of the density detection segments Sd and Sc are detected.

FIG. 5 shows, for example, at room temperature of about 20 ° C.
The waveforms of the applied voltage applied to the above-mentioned segments of the LCD 5 are shown, where V ₁ is the driving voltage and V ₂ is the bias voltage, and the driving voltage and the bias voltage have the best values. The contrast can be obtained.

On the other hand, FIG. 6 shows applied voltage waveforms when the temperature drops from the state of FIG. 5, where V ₁ 'is the drive voltage and V ₂ ' is the bias voltage. The best contrast can be obtained when the voltage is at these values.

That is, generally, in the LCD 5, the driving voltage and the bias voltage when the best contrast is obtained are changed by the temperature change. Therefore, in order to keep the LCD 5 in a good contrast, the LCD 5 is driven by the temperature rise. It is necessary to decrease the voltage and the bias voltage and increase the drive voltage and the bias voltage due to the decrease in temperature.

FIG. 7 is a block diagram of the camera shown in FIG. 1, and reference numeral 16 denotes a central processing unit (hereinafter referred to as CPU) which performs central control of the camera.

To the CPU 16, photometric data relating to the brightness of the subject is input from the photometric circuit 17, and sensitivity data relating to the film to be used is input from the sensitivity detecting circuit 18.

Further, the CPU 16 is supplied with state data of a switch interlocking with the release button 4 from the switch detection circuit 19, and from the A / D converter 30 density data relating to the density detection segments Sd and Sc. To be done.

The output from the CPU 16 is input to the driver 20, and the output from the driver 20 drives the shutter 21, the diaphragm 22 of the taking lens 2, and the motor 23 for film feeding.

The output from the CPU 16 is the LCD 5
It is input to the driver 24 for driving and the D / A converter 25, and the output from this driver 24 drives the LCD 5.

The LEDs 12 and 13 for light emission shown in FIG.
Is directly driven by the CPU 16 via the transistors 26 and 27, and the light passing through the concentration detecting segments Sd and Sc is converted into currents by the PTRs 14 and 15 and further converted into voltage by the resistors 28 and 29, A /
It is input to the D converter 30.

Then, the A / D converter 30 converts the density data relating to the density detecting segments Sd and Sc into digital signals and inputs them to the CPU 16. Figure 8
It is a flowchart showing the operation of the camera described above, and this flow starts when the release button 4 of the camera is pressed and the circuit of the camera is turned on.

First, the photometric data from the photometric circuit 17 is input (step S1). Next, the sensitivity of the film is read from the sensitivity detection circuit 18 (step S2). After that, calculation is executed based on the photometric data and the sensitivity of the film to obtain the proper exposure condition (step S3).

Next, the LCD 5 is driven to display (step S4). Details will be described later. After that, it is judged by the signal from the switch detection circuit 19 whether or not the shutter is released (step S5). When the shutter is not released, the process returns to step S1 to repeat the above process.

On the other hand, when the shutter is released, a mirror (not shown) is raised to retract from the optical path of the subject light (step S6). After that, the diaphragm 22 of the taking lens 2 is set to a predetermined value (step S7).

Next, the shutter 21 is opened and closed to expose the film for a predetermined time (step S8). After that, the motor 23 is rotated to feed one frame of film (step S9), the process returns to step S1, and the above process is repeated.

9 and 10 show step S4 of FIG.
This shows a subroutine of the display process of 1. First, the density detection segment Sd is turned on (step S10).
Next, the density detection segment Sc is turned off (step S11).

After this, the LEDs 12, 13 and the PTR 14,
15 is used to detect the density of the density detection segment Sd, and this is stored as data D (step S1).
2). Next, the density of the density detection segment Sc is detected using the LEDs 12 and 13 and the PTRs 14 and 15, and this is stored as data C (step S13).

Thereafter, the data C is subtracted from the data D,
The subtracted value is set as the density difference Δ ₁ (step S14).
Next, the output of the D / A converter 25 is set to 1
Step up (step S15), which causes the LCD
The drive voltage and bias voltage of No. 5 are increased by one step.

Thereafter, the LEDs 12, 13 and PT are further added.
The densities of the density detection segments Sd are detected by using R14 and R15 and stored as data D (step S16).

Next, the LEDs 12, 13 and the PTRs 14, 1
5 is used to detect the density of the density detection segment Sc, and this is stored as data C (step S1).
7). After that, the data C is subtracted from the data D, and the subtracted value is set as the density difference Δ ₂ (step S18).

Thereafter, the density difference Δ ₁ and the density difference Δ ₂ are compared (step S19 in FIG. 10), and when the values of the density difference Δ ₁ and the density difference Δ ₂ are the same value, the display data is output. (Step S20), display is performed on the display unit 6 (step S21), and thereafter, the process proceeds to step S5 shown in FIG.

On the other hand, when the value of the density difference delta ₁ and the density difference delta ₂ are not the same, it makes a comparison with the density difference delta ₁ and the density difference delta ₂ (step S22), and the density difference compared to the density difference delta ₂ Δ ₁
Is larger, the output of the D / A converter 25 is lowered by a predetermined two steps (step S23), whereby the drive voltage and the bias voltage of the LCD 5 are decreased by two steps.

Here, the output of the D / A converter 25 is decreased by two steps because it is already increased by one step in step S15 in the case of one step decrease.
This is because the output of the A / A converter 25 returns to the original state.

[0042] Thereafter, by replacing the values of the density difference delta ₂ to density difference delta ₁ (step S24), and then, LED12,13
And the PTR14, 15 are used to detect the concentration segment S
The density of d is detected and stored as data D (step S25).

Next, the LEDs 12, 13 and the PTRs 14, 1
5 is used to detect the density of the density detection segment Sc, and this is stored as data C (step S2).
6). Thereafter, the data C is subtracted from the data D, the subtracted value is set as the density difference Δ ₁ (step S27), and the process returns to step S19.

On the other hand, in step S22, the density difference Δ
_When the density difference Δ ₁ is smaller than that of ₂ , the density difference Δ _1
1 is replaced with the density difference Δ ₂ (step S28), and the process returns to step S15.

Incidentally, step S19 and step S2
The reason why the values of Δ ₁ and Δ ₂ are compared in ₂ is as follows. That is, in general, the relationship between the densities of the density detection segments Sd and Sc and the bias voltage is as shown in FIG.
In the relationship as shown in FIG. 1, there is almost no difference in density between the density of the density detection segment Sd which is always on and the density of the density detection segment Sc which is always off even if the bias voltage is changed. There is a region A where
In this area A, the density detection segments Sd and Sc
And the density difference between and becomes the largest, and the best contrast can be obtained.

Therefore, the density difference Δ before the bias voltage rises
₁ is compared with the density difference Δ ₂ after the increase of the bias voltage, and when these density differences do not change, it is determined that the bias voltage value exists in the area A, and the display is allowed in step S20 to allow the most display. It is possible to display in a good contrast state.

On the other hand, in step S22, when the density difference Δ ₁ before the increase of the bias voltage is smaller than the density difference Δ ₂ after the increase of the bias voltage, for example, when the bias voltage is in the region B in the figure, Sometimes step S28
As shown in, the density difference Δ ₁ is replaced with the density difference Δ ₂ , and the bias voltage is further increased by one step in step S15.

Further, in step S22, the bias
Concentration difference Δ before voltage rise₁However, after the bias voltage rises,
Difference Δ₂When it is larger, for example, the bias voltage
Is in the area C of step S23.
At, the bias voltage is reduced by two steps, after which
As shown in step S24, the density difference Δ₂Is the density difference Δ ₁
Is replaced by

Therefore, in the liquid crystal display density control device configured as described above, the density difference Δ between the density detecting segment Sd in the lit state and the density detecting segment Sc in the unlit state.
_Since the set voltage value when driving the liquid crystal display element is automatically adjusted according to ₁ and Δ ₂ , the segment density of the liquid crystal display element can always be adjusted to an optimum state.

As a result, at high temperatures, the segments of the liquid crystal display element that should be turned off do not appear dark, and conversely, at low temperatures, the segments that should be turned on do not appear thin, and the liquid crystal display is very easy to see. ..

Further, since the density is automatically adjusted, the adjustment of the density is not bothered, and it is possible to reduce the risk of missing an important photo opportunity. In addition,
In the embodiments described above, the example in which the liquid crystal display density control device of the present invention is applied to a camera has been described, but the present invention is not limited to such embodiments, and it goes without saying that it can be widely used for various electric devices and the like. Is.

In the embodiment described above, the density difference Δ ₁
And has been described as being configured such that the density difference delta ₂ outputs the display data when it is the same, the present invention is not limited to such embodiments, for example, density difference delta
_It goes without saying that the display data may be output when the value obtained by subtracting the density difference Δ ₂ from ₁ is within a predetermined value.

[0053]

As described above, in the liquid crystal display density control device of the present invention, the set voltage value for driving the liquid crystal display element is automatically adjusted according to the segment density in the lighted state and the segment density in the unlit state. Since this is done, the segment density of the liquid crystal display element can always be adjusted to an optimum state.

[Brief description of drawings]

FIG. 1 is a perspective view showing a camera having an embodiment of a liquid crystal display density control device of the present invention.

FIG. 2 is a top view showing details of the LCD of FIG.

3 is a cross-sectional view of the LCD of FIG.

4 is a perspective view showing a detecting means for detecting the density of a density detecting segment of the LCD of FIG.

5 is an explanatory diagram showing an applied voltage waveform of the LCD of FIG. 1 at room temperature.

6 is an explanatory diagram showing an applied voltage waveform when the LCD of FIG. 1 is heated.

FIG. 7 is a block diagram showing the camera of FIG. 1.

FIG. 8 is a flowchart for explaining the operation of the camera of FIG.

9 is a flowchart showing details of step S4 in FIG.

FIG. 10 is a flowchart showing details of step S4 in FIG.

FIG. 11 is an explanatory diagram showing the relationship between the density of the density detection segment and the bias voltage.

[Explanation of symbols]

 5 LCD 12,13 LED 14,15 PTR Sd, Sc Concentration detection segment

Claims (4)

[Claims] 1. A liquid crystal display element, driving means for driving the liquid crystal display element with a set voltage value, and detecting a density difference between a segment density in a lighted state and a segment density in a lighted state of the liquid crystal display element. A detection means, and a control means for changing the set voltage value when the drive means drives the liquid crystal display element, according to the segment density in the lit state and the segment density in the extinguished state detected by the detection means, A liquid crystal display density control device having. 2. The liquid crystal according to claim 1, wherein the control means changes the set voltage value to a voltage value when the density difference stops changing even if the voltage value is changed. Display density control device. 3. The liquid crystal display density control device according to claim 1, wherein the liquid crystal display element is provided with density detection segments for detecting segment density. 4. The detecting means includes a light emitting means for irradiating a segment of the liquid crystal display element with light, and a light receiving means for receiving the light passing through the segment. 4. The liquid crystal display density control device according to any one of 3 above.