JPS6310132A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To execute a ling drawing display having stable and uniform line width by controlling the generation quantity of a laser light by an output of a programmable read-only memory. CONSTITUTION:A torsion angle control signal VF of a galvanoscanner 20 and a line width control signal DLV are inputted from the outside, and the galvanoscanner driving circuit 1 drives the galvanoscanner 20 at a prescribed speed by a signal of VF, and simultaneously, detects a torsion speed of the galvanoscanner 20 by a speed detecting circuit 7. Subsequently, it is brought to an analog-to-digital (A-D) conversion, and inputted to a programmable read- only memory (PROM) 10. As for an input signal of the PROM 10, in addition to said signal, there are a line width signal WL, and a monitor signal M which has brought a laser power to an A-D conversion. By these three signals, a signal which is programmed in advance is outputted from the PROM, it is brought to a digital-analog (D-A) conversion, and a laser light is outputted by a laser driving circuit 11. An output of the PROM 10 can be set arbitrarily in accordance with each part, therefore, a stable and uniform display can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser power control method for a thermal writing liquid crystal display device, and particularly to a control method suitable for displaying a uniform line drawing.

[Conventional technology]

When realizing a thermal writing liquid crystal projection display device, the second
As shown in the figure, a galvano scanner is driven and a laser beam is generated to scan the liquid crystal cell by the action of both, and the image obtained from this is projected and displayed on a screen. An example of a related device of this type is US Pat. No. 3,836,243.

[Problem that the invention seeks to solve]

In the above conventional technology, when displaying a line drawing on a liquid crystal cell by scanning a laser beam with a galvano scanner, no consideration is given to the response speed due to the moment of inertia of the galvano scanner, and the line width of the line drawing is not uniform. The problem was that it didn't.

That is, in FIGS. 2 and 3, when Vp is given as a movement signal for the galvano scanner 20, the galvano scanner drive circuit 1 drives the galvano scanner 20. Simultaneously with the application of Vp.

The laser drive circuit 11 causes a current ILD to flow through the laser 5 to generate laser light. The laser beam scans the liquid crystal cell 4 to display a line image according to the deflection angle of the mirror 3, and when a predetermined deflection angle is detected by the deflection angle detection circuit 20, its generation is stopped.

Incidentally, the deflection angle θN of the galvanic mirror 3 exhibits a slow movement at the time of starting and stopping, as shown in FIG. 3, due to the moment of inertia of the mirror 3.

Therefore, near the starting point and ending point of the deflection angle of the galvanic mirror, the speed of the deflection angle is slow, so the amount of laser light irradiation increases, and as shown in Wt in FIG. In this case, the line width becomes thicker and uniform display becomes impossible.

Furthermore, no consideration was given to line width control suitable for a one-display display, stable output control of laser power, etc.

An object of the present invention is to obtain uniform line image display and a line width control function in a liquid crystal projection display, thereby obtaining good image quality.

[Means for solving problems]

The above purpose is achieved by controlling the amount of laser light irradiated onto the liquid crystal cell using the deflection angle velocity signal of the galvano scanner that scans the laser light, the line width control signal, and the laser power monitor signal. A liquid crystal projection display with high image quality can be realized.

[Effect]

In the configuration of the present invention, the deflection angle control signal Vp of the galvano scanner and the line width control signals Dt and v are inputted from the outside. Here, the vPtwm is specified from a computer or the like.

The galvano scanner drive circuit drives the galvano scanner at a predetermined speed using the Vp signal as in the conventional example.

Meanwhile, at the same time, the speed detection circuit detects the deviation speed of the galvano scanner.

This is then converted from analog to digital (A-D) to create programmable read-only memory (FRO).
M).

In addition to this, the input signals of the FROM are a line width signal WL and a monitor signal M obtained by AD converting the laser power.

These champion signals output pre-programmed signals from FROM and convert them into digital-to-analog (D
-A) Convert and output laser light using a laser drive circuit.

The output of the FROM, ie, the laser power, is controlled by the above-mentioned signal, but the non-uniformity of the line width at the start and end points of the deflection of the galvano scanner is corrected by the signal from the speed detection circuit. Further, fluctuations in laser power due to changes in ambient temperature, etc. are corrected by the monitor signal. Furthermore, the line width is controlled by a signal set directly from the outside.

The FROM output can be set arbitrarily according to variations in the characteristics of individual parts.

Stable and uniform display is possible.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1, 4, and 5.

FIG. 1 shows an example of the configuration of the present invention, and FIG. 4 is a time chart of main signals.

In FIG. 1, what is set from the outside is a control signal Vp that biases the galvano scanner 2o to a predetermined angle at a predetermined speed, and a digital signal DLV for setting the line width.
It is.

The control signal Vp is applied to the drive circuit 1 to drive the galvano scanner 20. The galvano scanner 2o is the drive unit 2
The liquid crystal cell 4 is irradiated with laser light and scanned by the deflection angle of the mirror 3.

The deviation angular velocity detection circuit 7 detects the deviation angular velocity of the galvano scanner 20. Since the deflection angle θ of the galvano scanner 20 has a moment of inertia, it changes gradually with respect to the time axis t at the starting point and the ending point, as shown by the broken line in FIG. 4(b).

Therefore, the output VM of the deviation angular velocity detection circuit 7 becomes a signal at a constant level at the center where Vp is changing, as shown in FIG. 4(c). Then, this signal is converted into □analog-to-digital (A-D).

Program read only memory (FROM) is
The output of the A-D converter 8, a digital signal DL for setting the line width, and a digital signal DH for monitoring the laser output are input. Here, the monitor signal DH is a signal obtained by detecting the laser output with the photodiode 6 and the current detector 13 and digitizing this signal with the AD converter 12.

Note that the monitor signal DM is a feedback signal that monitors changes in laser power due to changes in the surrounding area, etc., and obtains stable laser power, but unlike a normal analog system, it constantly monitors the laser power. It's not something you do.

Now, the output signal of FROM is digital-analog (
D-A) The converter 9 converts the signal into an analog signal, and the laser drive circuit 11 causes a current Io to flow through the laser to generate laser light.

The laser current It,o is output depending on the input signals of the FROM, that is, the deflection angular velocity of the galvano scanner 2o, the line width, and the monitor signal (5). The output waveform is almost the same as the deviation angular velocity signal VM, as shown in FIG. 4(d).
This is a signal whose level changes depending on the line width signal. Therefore, since the power density of the laser beam irradiated onto the liquid crystal cell 4 is constant, the line drawing WL drawn on the liquid crystal cell becomes sharp as shown in FIG. 4(e).

By the way, the relationship between this FROMIO address and output is programmed as shown in FIG. 5, for example. In FIG. 5, the lower part of the address Ao'' A2 is the deviation angular velocity signal VMf), the central part Aa, A+ is the line width signal Dm,
The upper parts Aδ and As are address signals used as monitor signals M.

When the monitor signals A a and A 6 = O, and the line width signal Aa and the A number = 0, the deviation angular velocity signals AO to Ax
It outputs a data signal D o '' D 7 proportional to .

On the other hand, the line width signal is Aa=' 1 ' e A4=' O
' (7) In the case, the output signal is
Program it to double. The line width at this time is twice that of the above.

Furthermore, the monitor signal is As” '1', Aa='O
In the case of ', for example, the output is not output unless the deviation angular velocity signals AO to A2 exceed a certain level. Of course, it is also possible to do the opposite.

The output value of A o '' A z can be arbitrarily set depending on the laser driving conditions.

Since these output signal amounts are the outputs of the FROM, they can be set arbitrarily depending on the laser characteristics, the response characteristics of the galvano scanner, etc. Also, changes in characteristics due to variations in individual parts can be easily corrected. can do.

〔Effect of the invention〕

According to the present invention, the amount of laser light generated is programmable.
Since it is controlled by the output of the read-only memory, the output amount can be arbitrarily set in consideration of the characteristics of the galvano scanner and the characteristics of the laser. Therefore, there is an effect that line drawings with stable and uniform line width can be displayed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional example, FIG. 3 is a timing diagram of a conventional example, and FIG. 4 is a timing diagram of an embodiment of the present invention. FIG. 5 is an explanatory diagram showing the relationship between addresses and data in FROM of the present invention. 4...Liquid crystal cell, 5...Laser, 7...Speed detection circuit, 1st port figure

Claims (1)

[Claims] 1. A laser beam generator, an optical means for two-dimensionally scanning the laser beam, and a liquid crystal element sealed with a liquid crystal material having a thermo-electro-optic effect, and the laser beam and the optical means: In a liquid crystal display device that forms an image on a liquid crystal element and projects the image onto a screen,
A liquid crystal display device comprising means for detecting the scanning speed of the optical means and controlling the amount of laser beam generated in accordance with the scanning speed.