JPS62206528A - Writing method in liquid crystal light valve - Google Patents

Abstract

PURPOSE:To enable writing in a liquid crystal light valve at high speed by means of a semiconductor laser by elevating the temp. of a writing section to a lower first temp. by means of a first laser beam, then executing writing by elevating the temp. to a second temp. by means of second laser beam. CONSTITUTION:Preheating beam 1 for elevating the temp. of liquid crystal is emitted prior to the emission of writing laser beam 2, and the preheating beam is allowed to scan at the same time with the scanning operation using the writing laser beam 2. In this case, the preheating beam 1 is not necessarily laser beam convergible to one point, but may be flat convergible beam longitudinally in the scanning direction. Such beam is obtd. by using high output laser shutting up oscillated light loosely ni the lamellar direction of an activated layer of semiconductor laser. The temp. is set at far lower temp. T0 than the bias temp. T1 of the liquid cell, elevating the temp. to above the liquid crystal temp. T1 by irradiating with preheating beam from the time t1, and elevating further the liquid crystal temp. upto T2 by irradiating with writing laser beam at a time point t2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a writing method for liquid crystal light valves (liquid crystal projection display devices) using laser thermal writing.

(Prior Art) Display devices used in comviator terminal devices are required to have increasingly high resolution resolution due to the increased capacity and improved functionality of computers. Particularly in image processing using a combinator, editing of newspaper pages, and LSI design, a display with high precision and which can be partially rewritten is desired.

In conventional equipment, it is difficult to increase the resolution of the CRT (cathode ray tube) used above 2,000 lines, and the scanning speed of the electron beam also increases, causing flickering on the screen. In addition, display devices using storage tubes are
The disadvantages are that the screen brightness is low to prevent deterioration of the phosphor, partial erasure cannot be performed, and the device is expensive.

In recent years, displays that thermally write with liquid crystal laser light have been viewed as promising as display devices with a resolution of 2,000 lines or more. (Proceeding of the
S・I・D) J 1978, pages 1-7 [Laser Selective Liquid Crystal Projection Display (LASER
,ADDRESSED LIQUID CRYSTAL
PROJEC-TION DISPLAYS) J.

According to this paper, as shown in FIG. 7, an image can be recorded on a liquid crystal light valve 50 by scanning with a laser beam 58, and a projected light 59 can be reflected on this recording to display the image. This liquid crystal light valve 50 includes a glass substrate 51 on which a laser light absorption film 52, an aluminum reflection film 53, and a liquid crystal alignment film 54 are formed, and a glass substrate on which a transparent electrode film 55 and a liquid crystal alignment film 54 are formed. 57 and a liquid crystal material 56 sandwiched therebetween. When the laser light 58 enters the liquid crystal light valve 50, the laser light 58 is absorbed by the laser light absorption film 52 and converted into heat, which passes through the aluminum reflection film 53 and the liquid crystal alignment film 54 to increase the temperature of the liquid crystal material 56. A smectic liquid crystal is used as the liquid crystal material 56, and the smectic liquid crystal changes into a nematic phase and a liquid phase as the temperature rises, and is rapidly cooled when the laser beam 58 is removed. At this time, the orientation state of the liquid crystal molecules in the liquid state is frozen and scattering nuclei are formed, and these scattering nuclei are read out by the projection light 59 and displayed as pixels on the screen. These scattering nuclei can form lines with a width of about 10 μm, so as many as 5,000 lines can be recorded on a 2-inch square liquid crystal light valve, making it possible to create displays with much higher resolution than conventional CRTs. It becomes possible. Note that in order to erase this display screen, an electric field may be applied between the aluminum reflective film 53 and the transparent electrode film 55 to reorient the liquid crystal.

A display using such a liquid crystal light valve can use a high-brightness projection light source, so it is possible to display a large screen with high brightness and high precision. However, because it is thermally written by scanning with a laser, the display speed is proportional to the amount of laser light.

For this reason, high-output YAG lasers and argon lasers are used as laser light sources for laser thermal writing type liquid crystal projection displays.

(Problem to be solved by the invention) However, using this type of high-power laser requires a large device and large power consumption, and is limited to special applications.Recently, attempts have been made to use semiconductor lasers. ing. However, the output of this semiconductor laser is one order of magnitude lower than that of a high-output laser, and the display speed is extremely slow, making it impossible to obtain a high-contrast display. For this reason, some attempts have been made to improve the display speed by guiding a large number of laser beams with 7 eyebars to form an array light source and writing in parallel, but using a large number of semiconductor lasers is difficult due to equipment maintenance and cost. It is not practical in this respect. In addition, recently, high output lasers of 100mW or more have become available as single semiconductor lasers. It is not used as a laser light source for displays.

(Object of the Invention) An object of the present invention is to provide a liquid crystal light valve writing method that can write to a liquid crystal light valve at high speed using a semiconductor laser.

(Structure of the Invention) The structure of the present invention is that in a liquid crystal light valve writing method in which an image is written on the liquid crystal cell by scanning a laser beam and heating a writing part of a liquid crystal cell to a temperature higher than the writing temperature, the laser beam is Using at least a first laser beam and a second laser beam output following the first laser beam, the first laser beam lowers the temperature of the writing section to a first temperature lower than the writing temperature. raise the temperature to
Writing is performed by raising the temperature of the writing section to a second temperature higher than the writing temperature using the 20th router beam.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1(a) is a side view of a laser beam showing a first embodiment of a writing method for a liquid crystal cell using a laser beam according to the present invention. a preheating beam 1 for increasing the temperature of the liquid crystal prior to the writing laser beam 2;
Scan simultaneously with writing laser beam 2. At this time, the preheat beam 1 does not need to be a laser beam that can be focused on one point, and a flat focused beam that is long in the scanning direction as shown in the figure can be used. Such a beam can be obtained by using a laser whose output is increased by loosening the confinement of the oscillated light in the layer direction of the active layer of the semiconductor laser.

FIG. 1 Φ) is a characteristic diagram showing the temperature change at the laser writing point of the liquid crystal cell in this first embodiment.

In the conventional method, as shown by the broken line A, the bias temperature T1
was given in advance, the liquid crystal was irradiated with a writing laser beam at time t2 to raise the temperature to T2, and when the temperature of the liquid crystal decreased, writing was performed on the liquid crystal in a scattered state. , as shown by the solid line B, the temperature To is set much lower than the bias temperature T1 of the liquid crystal cell, and from time t1, the liquid crystal temperature is raised to above T1 by preheat beam irradiation, and at time t2, the writing laser beam is irradiated. to raise the liquid crystal temperature to T2. At this time, since the liquid crystal temperature is locally heated by the preheat beam, the temperature at the laser writing point rapidly decreases as shown by the solid line B after laser writing. The rate of fall of the liquid crystal temperature determines the strength with which the liquid crystal becomes in a scattering state; the faster the rate of fall is, the stronger the scattering state is, and the higher the contrast obtained in the display. Conventional temperature drop curve A
A comparison between the curve B and the temperature drop curve B according to the present invention shows a large difference, and it is clear that the writing method according to the present invention improves the contrast.

FIG. 2(a) is a side view of a laser beam according to a second embodiment of the invention. This embodiment shows a writing method for a liquid crystal cell using a laser beam, in which a writing beam 12 is superimposed on a preheat beam 11. Now, the preheat beam 11 is
Three condensed beams lla, llb, and IIC that cannot be made into one point
Suppose it is made up of beams. Such a semiconductor laser beam can be obtained by using a high-power semiconductor laser that integrates a plurality of active regions. It is possible to match the position of the writing laser beam 12 with the last beam 11G in the scanning direction among these preheat beams 11. The temperature change at the laser writing point of the liquid crystal cell obtained at this time is as shown in FIG. 2 Φ). Time t1 when these preheat beams lla and llb cross the laser writing point
At t2, the temperature rises to T1, and finally due to the preheating beam 11C and the writing laser beam 12, the temperature reaches T2. The effect of this is similar to that of the first embodiment.

FIG. 3 is a configuration diagram showing an example of an optical head that embodies the method of this embodiment and generates a preheat beam and a writing laser beam. The optical head combines a laser beam from a semiconductor laser 21 with good focusing and a high-output semiconductor laser 22, and combines the laser beam emitted from the semiconductor laser 21 and transmitted through the collimating lens 23 and the polarizing prism 25, and the laser beam from the semiconductor laser 21. 22, passes through a collimator lens 24, and is reflected by a polarizing prism 25, and is combined with the laser beam to obtain a composite beam 26. At the ninth point when the two laser beams are combined by the second polarizing prism 25, the two semiconductor lasers 21 and 22 are installed so that their polarization planes are perpendicular to each other. In addition, in order to obtain the circularity of the laser beam, collimating lenses 23 and 24 and polarizing prisms 2
It is also possible to insert a beam shaping optical system such as a prism or a cylindrical lens between the 50° and 50°. The relative position of the preheat beam from the high-power laser 22 and the writing laser beam from the semiconductor laser 21 with good focusing is determined by the polarizing prism 25.
It can be set arbitrarily by adjusting the angle. Drive circuit 2
0, the semiconductor laser 22 is always stably operated at high output, and the semiconductor laser 21 is switched in accordance with the image signal.

FIG. 4 is a configuration diagram showing an example of a projection display device using this embodiment. The laser beam from the optical head 31 is scanned two-dimensionally by the scanning mirror 32, focused on the liquid crystal light valve by the writing lens 33, and then scanned by the scanning mirror 3 by the control circuit 40.
An image signal is sent to the optical head 31 in synchronization with 2, and an image is written on the liquid crystal 2-ite pulp 34. The image written on the liquid crystal light valve 34 is created by projecting light 39 from a projection light source 38 onto the liquid crystal light valve 34 using a condensing lens 37 and a projection lens 35, and folding the reflected light back at a mirror 36. Therefore, it is projected onto the screen.

In this embodiment, the writing semiconductor laser output 39
mW, high power semiconductor laser output for preheat beam 10
By using 0 mW, the temperature drop rate at the writing point of the liquid crystal cell can be improved by one order of magnitude, and the contrast of the displayed image can be improved by one order of magnitude.
．． We were able to improve it five times. Furthermore, if the same contrast as before was obtained, the display speed could be increased by 1.5 times.

(Effects of the Invention) As described in detail above, according to the present invention, by using a high-output semiconductor laser with poor light focusing ability, a liquid crystal light valve writing method with higher contrast or higher speed than conventional methods can be realized. Enables high-speed, high-contrast display of laser thermal writing liquid crystal projection displays.

[Brief explanation of drawings]

Figure 1 (Figure 2) is a side view showing two embodiments of the laser beam writing method on a liquid crystal cell according to the present invention during beam projection; A characteristic diagram showing a temperature change at a writing point of a liquid crystal cell according to an embodiment, FIG. 3 is a configuration diagram of an example of an optical head for realizing this invention, and FIG. 4 is a diagram of an example of a projection display device using this invention. FIG. 5 is a cross-sectional view of an example of a conventional liquid crystal light valve used in the present invention. 1.11...Breheat Beam, 2.12...
・Song writing laser beam, 20...drive circuit,
21゜22... Semiconductor laser, 23.24...
...Collimating lens, 25...Polarizing beam splitter, 31...Optical head, 32.
・Scanning mirror, 33.35.37...
・Lens, 34...LCD light bulb, 36・
...Mirror, 38...Projection light source, 39.
...Projection light, 40...Control circuit, 50.
...Liquid crystal, 51.57...Glass base,
52. Old... Laser light absorption film, 53... Aluminum reflective film, 54... Liquid crystal alignment film, 55...
- Transparent electrode film, 58... Laser light, C'. Agent: Patent Attorney Uchi Hara, Shincho I Prisoner (twice)

Claims (1)

[Scope of Claims] 1) In a liquid crystal light valve writing method in which an image is written on a liquid crystal cell by scanning a laser beam and heating a writing part of a liquid crystal cell to a temperature higher than a writing temperature, at least using one laser beam and a second laser beam outputted following the first laser beam, the temperature of the writing section is set to a first temperature lower than the writing temperature by the first laser beam. A liquid crystal light valve writing method characterized in that writing is performed by raising the temperature of the writing section to a second temperature higher than the writing temperature using the second laser beam. 2) The liquid crystal light valve writing method according to claim 1, wherein the first temperature is a temperature of a smectic phase of a liquid crystal used in a liquid crystal cell, and the second temperature is a temperature of a liquid phase of the liquid crystal. 3) A patent claim characterized in that the first laser beam consists of a plurality of beams, and one of the laser beams and the second laser beam are focused at the same location on the liquid crystal cell. The liquid crystal light valve writing method described in item 1.