JPH0723940B2 - Liquid crystal projection type writing position correction device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projection type display writing position correction apparatus, and particularly to a liquid crystal projection suitable for a control system for writing a figure or the like by laser beam irradiation which requires high resolution. The present invention relates to a writing position correction device for a display.

[Background of the Invention]

Conventional liquid crystal projection type display (projection type liquid crystal display device)
Regarding the laser beam writing method of "Display Advanced Technology Collection (Second
Version) "59.1.15, p. 351-356, Chapter 4," Projection-type liquid crystal display device "(a) Laser beam writing method, as described in" Laser beam writing method ". The function of the Y-axis and Y-axis galvanometer mirrors as an optical axis controller for controlling the is known. This laser beam writing method controls the optical axis of the laser beam by an X-axis and Y-axis galvanometer mirror, which is an optical axis controller, and scans it two-dimensionally, and writes figures etc. in a liquid crystal element having a memory function. In order to erase the displayed line segment, it is necessary to re-irradiate the same line segment. However, the conventional writing method does not take into consideration the effects of the aged drift of the Y-axis and Y-axis galvano mirrors that form the optical axis controller and the electrical and mechanical drifts during long-term continuous operation. In the practical application of the liquid crystal projection type display by the laser beam writing method, there is a problem that the drift of the optical axis controller causes the distortion of the displayed figure and the leakage of the erased line segments. Atsuta

[Object of the Invention]

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a liquid crystal projection type display position correction device which automatically corrects the drift of the optical axis controller and enables high-resolution and high-precision laser beam writing. To provide.

[Outline of Invention]

The present invention relates to a liquid crystal projection type display laser beam writing system, which is a liquid crystal projection type display writing position correcting device for detecting an irradiation position of a laser beam by a position detector to correct an optical axis controller of the laser beam. Preferably, a position detector provided with a slit in the cross direction is arranged at a corresponding position on the same plane as the laser beam irradiation surface of the liquid crystal element, and the laser beam is drawn so as to draw a square locus on the position detector. The irradiation position of the laser beam that has been irradiated and has passed through the slit is detected, and the movement deviation and rotation deviation of the laser beam in the vertical and horizontal directions are calculated, and the irradiation position of the laser beam is automatically corrected by the optical axis controller. Is a liquid crystal projection type display writing position correction device.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS.

First, FIG. 1 is a block diagram of the entire configuration showing an embodiment of a writing position correction system of a liquid crystal projection type display according to the present invention. In FIG. 1, 1 is a writing control unit, 2 is a laser for generating the laser beam, 3 is an optical axis controller for controlling the optical axis of the laser beam to perform two-dimensional scanning, and 4 is a laser emitted from the laser 2. Beam intensity and optical axis controller 3
It is a writing control circuit for controlling the two-dimensional position (angle) of the optical axis of the laser beam emitted from. Reference numeral 5 denotes a liquid crystal element whose transparency changes by laser beam irradiation utilizing the thermo-electro-optic effect of smectic A-phase liquid crystal. 6 is a projection optical unit,
Reference numeral 7 is a light source for giving projection light to the liquid crystal element 5, 8 is a lens, 9 is a half mirror, 10 is a projection lens for magnifying the reflected light from the liquid crystal element 5, and 11 is a screen. Reference numeral 12 denotes a screen controller that creates control data for creating a figure and the like for the writing control circuit 4 and voltage data for creating a figure and the like for the liquid crystal element 5. Reference numeral 13 is arranged on the same plane as the laser beam irradiation surface of the liquid crystal element 5 according to the present invention, the position thereof is detected by laser beam irradiation, and the positional information is given to the screen controller 12 to shift the position of the optical axis controller 3. It is a position detector for correction. With this configuration, the write controller 1 is instructed by the screen controller 12
By controlling the light amount of the laser beam emitted from the laser 2 by the writing control circuit 4 and controlling the two-dimensional position (angle) of the laser beam emitted from the optical axis controller 3 by the writing control circuit 4. The optical axis of the laser beam is two-dimensionally scanned through the X-Y axis via 3, and a figure or the like is written and stored in the liquid crystal element 5 utilizing the thermoelectro-optical effect of the smectic A-phase liquid crystal by the laser beam irradiation. The details of the structure and writing principle of the liquid crystal element are described in the above-mentioned publicly known examples, pp. 351-352. The projection light from the light source 7 of the one projection optical unit 6 is converted into parallel rays by the lens 8 and half the amount of light is given to the liquid crystal element 5 by the half mirror 9 and given to the liquid crystal element 5. The light is reflected by only the portion other than the figure (line segment) written by the laser beam irradiation from the optical axis controller 3 in the writing control unit 1, and the half mirror 9 again.
After passing through, the image is enlarged through the projection lens 10 and projected on the screen 11. Here, the two-dimensional light flux reflected from the liquid crystal element 5 is a light flux indicating a figure or the like written in the liquid crystal element 5, and the light flux indicating this figure or the like is enlarged by the projection lens 10 and is projected on the screen 11 or the like. , And the figure etc. written in the liquid crystal element 5 by the writing control unit 1 is displayed. The operation of the position detector 13 according to the present invention will be described next.

FIG. 2 is a perspective view of a basic configuration of a laser beam optical system including the position detector 13 according to the present invention shown in FIG. In FIG. 2, the same reference numerals as those in FIG. 1 denote the same or corresponding portions throughout the drawings, 14 is a Y-axis galvanometer mirror that constitutes the optical axis controller 3, and 15 is an X-axis galvanometer mirror. is there. With this configuration, the laser beam emitted from the laser (oscillator) 2 is incident on the optical axis controller 3 including the Y-axis galvanometer mirror 14 and the X-axis galvanometer mirror 15, and the two laser beams for the Y-axis and the X-axis are used. By rotating the Galvano mirrors 14 and 15 respectively in the directions of the arrows, the optical axis of the laser beam is controlled to perform two-dimensional scanning along the X-Y axis. ) Etc. are written. However, the Y-axis and X-axis galvanometer mirrors 14 and 15 of the optical axis controller 3 generate a drift when performing continuous operation for a long time, which causes a positional deviation in the laser beam irradiation position and distorts a figure or the like. No Further, the diameter of the laser beam spot irradiated onto the liquid crystal element 5 is about several μm, which is very small, and in order to erase a part of the line segment written on the liquid crystal element 5, it is necessary to irradiate the written line segment again. However, if scanning is performed without completely irradiating the same line segment, the line segment cannot be erased and remains on the liquid crystal element 5. In order to prevent these, according to the present invention, the position detector 13 installed on the same plane as the liquid crystal element 5 is irradiated with a laser beam and the irradiation position of the laser beam is detected, so that the position information is fed back. Then, the positional deviation due to the drift of the Y-axis and X-axis galvanometer mirrors 14 and 15 of the optical axis controller 3 is corrected.

3 (a), (b), and (c) are a perspective view, a plan view, and a laser beam irradiation plan view of the position detector 13 of FIGS. 1 and 2, respectively. In FIG. 3 (a), 16 is a position sensor plate (position detecting element) that constitutes the position detector 13,
Reference numeral 17 is a laser beam shield plate also provided on the front surface thereof with four slits of about several μm. In FIG. 3 (b), the four slits of the laser beam shielding plate 17 are shown by solid lines, and their positional relationship is in the cross direction (X
-Y four directions). In FIG. 3 (c), the trajectory of the laser beam when the laser beam shield plate 17 of the position detector 13 is irradiated when there is no positional deviation (drift) of the laser beam is shown by broken lines, and the position shape is different. 4 vertices
Make a square that intersects the slits of a book. If a positional deviation (drift) of the laser beam occurs, correction is performed so that the trajectory of the laser beam returns to the state shown in FIG. 3 (c). Further, FIG. 4 shows the position detector 13 of FIG.
6 is an equivalent circuit diagram of the position sensor plate (position detecting element) 16 of FIG. In FIG. 4, 18 is a laser beam receiving surface, 19 is a current source that converts a laser beam into a photocurrent, 20 and 21 are X-axis position detection outputs (terminals), and 22 and 23 are Y-axis position detection outputs (terminals). Is. With this configuration, the laser beam applied to one point on the laser beam receiving surface 18 is converted into photocurrent on the light receiving surface. The photocurrent of the current source 19 is distributed according to the resistance ratio up to the X-axis position detection outputs (terminals) 20 and 21 and the resistance ratio up to the Y-axis position detection outputs (terminals) 22 and 23. The detection outputs (terminals) 20 and 21 and the Y-axis position detection outputs (terminals) 22 and 23 can be taken out, and the X-axis and Y-axis positions of the laser beam irradiation point can be calculated from the current value ratios. . The position detector 13
The details of the structure and the detection principle of the position sensor plate (position detecting element) 16 of are described in Hamamatsu Photonics KK catalog "Semiconductor position detecting element (PSD)" T84 ・ 3 ・ 20.

FIG. 5 is a basic block diagram of a laser beam position correction control system including the position detector 13 according to the present invention shown in FIG.
In FIG. 5, reference numeral 24 is a position detection circuit for converting the output of the position detector 13 into digital position information. With this configuration,
The position detection output detected by the position detector 13 is converted into a digital signal through the position detection circuit 24, and the position information 25 is read out by the screen controller 12, and a simple correction calculation is performed by the position correction algorithm, and the position including the correction value is read. A command 26 outputs a control signal 27 including a correction value to the optical axis controller via the writing control circuit 4. FIG. 6 is a circuit block diagram of the position detection circuit 24 of FIG. In FIG. 6, 28 is a Y-axis position detecting unit, 29 is an X-axis position detecting unit, 30, 31.
Is a Y-axis position b, d storage register, 32, 33 is an X-axis position a, c storage register, 34 is a Y-axis data storage signal, and 35 is an X-axis data storage signal. With this configuration, the Y-axis positions b and d and the X-axis position a of the laser beam of the square locus (indicated by the dashed arrow) incident on the position sensor plate 16 of the position detector 13 through the four slits of the laser beam shield plate 17 are shown. , c detected Y-axis position detection outputs (terminals) 22 and 23 and X-axis position detection outputs (terminals) 20 and 21 are the photocurrent values of the Y-axis and X-axis position detectors 28 and 29 of the position detection circuit 24. Is converted into digital position information of each Y-axis position b, d and X-axis position a, c, and each Y-axis position b, d register 30, 31, X by each Y-axis, X-axis data storage signal 34, 35. Axis position
The position information 25 stored in the a, c registers 32, 33 is read by the screen controller 12 and correction calculation is performed by the position correction algorithm as follows.

7 (a), (b), and (c) are mainly vertical and horizontal directions (X-Y directions) performed by the screen controller 12 of FIG. 5 by detecting the position of the laser beam of the position detector 13 of FIG.
FIG. 7 is a plan view for explaining each correction procedure of the movement deviation of FIG. In FIG. 7 (a), the case where the position detector 13 irradiates the laser beam with vertical and horizontal displacements and rotations is illustrated, and FIG. 3 (c) corresponds to the solid line slits. With respect to the locus of the laser beam irradiated on the square when there is no positional deviation shown by the broken line, the position shown by the broken line corresponding to the slit in the vertical and horizontal directions (XY direction) shown by the solid line in FIG. When there is a deviation, the locus of the laser beam applied to the square is deviated in the vertical and horizontal directions and the rotational direction. That is, the center of the square moves from the center of the slit to the center position p ₀ , and the rotation angle θ ₀ also deviates. In this state, the position sensor plate 16 of the position detector 13 can detect the laser beam irradiation position through the four slits of the laser beam shield plate 17 because the solid line four slits and the broken line square in FIG. 7 (a). 4 points q _{0 to} q ₃ which are intersections with the locus of the laser beam. The values of these four points q _{0 to} q ₃ can be input from the position detector 13 to the screen controller 12 as digital position information 25 via the position detection circuit 24. The screen controller 12 detects these four points q ₀
The center p ₁ (p ₁ x, p ₁ y) of the rectangle formed by drawing a straight line in the horizontal and vertical directions shown by the alternate long and short dash line in the figure through ~ q ₃ is obtained by the following formula.

However, q _{0 to} q _{3 and the} like in the equation (1) similarly indicate XY coordinate values of the points q _{0 to} q _{3 and the} like. Thus calculated Matsuda center p ₁ value _{(p 1 x, p 1 y} ) = (Δx, Δy) as a correction value of the movement displacement of the center p ₁ via the write control circuit 4 so as to coincide with slit intersection The drift of the optical axis controller 3 is corrected. Figure 7 (b), the this manner is exemplified when corrected movement shift, rectangular central forming four points q ₄ to q ₇ that is positioned similarly detected in this state coincides with the slit center Correct the movement deviation so that In FIG. 7 (c), the case where the movement deviation is further corrected is illustrated, and by repeating the movement deviation correction depending on the state, the center p ₁ of the rectangle of the alternate long and short dash line and the slit of the solid line are gradually increased. The displacement is corrected so that the center of the slit coincides with the center of the slit and the center p _{0 of the} trajectory of the laser beam of the broken-line square coincides with the center of the slit. The determination that the correction of the movement displacement in the vertical and horizontal directions is completed is performed by the following equation.

However, Δ ₁ is a minute constant.

Next, FIGS. 8 (a), (b), and (c) are plan views for explaining each correction procedure of the rotational deviation. In FIG. 8A, the case where the correction of the movement deviation in the vertical and horizontal directions in FIG. 7C is completed and the rotation deviation of the rotation angle θ ₀ remains is illustrated. Corresponding to the slit in the (X-Y direction), the locus of the square laser beam shown by the broken line is shifted by the rotation angle θ ₀ . In this state, the position detector 13 can detect the laser beam irradiation position through the slit in the Y-axis direction, for example, at two points r ₀ and r ₁ , and from the point r ₁ to the point r _0.
Let l _{1 be} the length of the Y-axis up to. Similarly, the laser beam irradiation positions that can be detected through the slits in the Y-axis direction of the square laser beam locus after correction of the rotational deviation indicated by the one-dot chain line are points r ₂ and r ₃ , and from point r ₂ to point r _3. The length of the Y-axis up to is set to l ₂ . That is, Y before and after correction of the rotational deviation
The axis lengths l ₁ and l ₂ are given by the following equations.

_{l 1 = r 0 -r 1,} l 2 = r 2 -r 3 ......... (3) provided that ₍₃₎ r ₀ ~r 3 in formula is Y coordinate values of each point r ₀ ~r _3. Comparing the length l ₁ before the correction and the length l ₂ after the correction, it is illustrated in FIG. 8 (a) that the rotation deviation is corrected correctly. In the case of this correction, The following conditional expression is satisfied.

l ₁ l ₂ (4) Further, in FIG. 8 (b), the case where the rotation deviation is corrected in the opposite direction is illustrated. In this case, l ₁ > l _{2 and the} formula (4) is obtained. Does not hold. Further, in FIG. 8 (c), the rotation deviation is corrected in the same direction as in FIG. 10 (a), but an example of overcorrection is illustrated. In this case also, l ₁ > l ₂ ( It shows that the equation (4) is not satisfied. In this way, the length before correction l ₁ and the length after correction
while comparing the l _2, (4) expression while l ₁ l ₂ conditions are satisfied repeatedly performs correction, to complete the correction and l ₁ l ₂ is not satisfied. The determination that the correction of the rotation deviation is completed is performed by the following equation.

Δ = l ₂ −l ₁ Δmin (5) However, Δmin is a positive minute constant. The screen controller 12 performs write control while performing a simple calculation of the above-described position correction algorithm for movement displacement and rotation displacement in the vertical and horizontal directions based on the position information 25 detected by the position detector 13 and converted through the position detection circuit 24. After the correction of the optical axis controller 3 is completed via the circuit 4, a position command including the above-mentioned correction value of the liquid crystal element is output.

Next, FIG. 9 is a perspective view of a concrete configuration of a laser beam optical system showing an embodiment of a writing position correction system of a liquid crystal projection type display according to the present invention. In FIG. 9, 36 is a beam expander, 37 is a Y-axis stage to which the Y-axis galvanometer mirror 14 is attached, and 38 is an X-axis galvanometer mirror 15.
Is an X-axis stage, and 39 is an f-θ lens. The Y-axis and X-axis galvanometer mirrors 14 and 15 are equipped with control circuits (driving circuits) for the respective galvanometer mirrors.
A control circuit for each stage is mounted on each of the axis and X-axis stages 37 and 38, and a pulse motor is attached to the axis and X-axis stages 37 and 38. The axis and X-axis stages 37 and 38 have a function of correcting the deviation of the mirror axes of the Y-axis and X-axis galvano mirrors 14 and 15. With this configuration, the beam diameter of the laser beam emitted from the laser (oscillator) 2 is expanded by the beam expander 36, and the Y-axis galvanometer mirrors 14 and X of the optical axis controller 3 are expanded.
The liquid crystal element 5 is scanned two-dimensionally in the XY directions via the axis galvanometer mirror 15 and is irradiated onto the liquid crystal element 5 via the f-θ lens 39. Also, FIG. 10 is a block diagram of a concrete configuration of the laser beam control system. In FIG. 10, reference numerals 40 and 41 are X-axis and Y-axis position detecting circuits constituting the position detecting circuit 24.
42 and 43 are D / A converters constituting the write control circuit 4, 44 and 45
Is a pulse generating circuit, and 46 and 47 are driving amplifiers. Reference numeral 48 is a CPU (central processing unit) that constitutes the screen controller 12, and 49 is a memory. With this configuration, the current values corresponding to the X-axis and Y-axis positions of the laser beam irradiation detected by the position detector 13 are converted into voltage values by the X-axis and Y-axis position detection circuits 40 and 41, and then A / D. The converted data is provided to the CPU 48 as digital data of position information of X and Y coordinates. The Y-axis and X-axis galvano mirrors 14 and 15 are provided with control circuits (driving circuits) for the respective galvano mirrors, and the CPU 48 outputs the Y-axis and X-axis control circuits.
Output values obtained by converting the Y-axis and X-axis position (angle) commands into analog amounts by the D / A converters 42 and 43 and the Y-axis and X-axis galvano mirrors 14 and 15 according to the axis position (angle) command. After matching with the Y-axis and X-axis position (angle) feed back values from, the deviation value is amplified by each drive amplifier 46, 47 as a movement signal of each Y-axis, X-axis galvano mirror 14, 15. The Y-axis and X-axis galvanometer mirrors 14 and 15 are applied and driven. Furthermore each Y
The control circuit of each stage is mounted on the Y-axis and X-axis stages 37 and 38 of the X-axis and X-axis galvanometer mirrors 14 and 15, and a pulse motor is attached, and a pulse is generated by each Y-axis and X-axis command from the CPU 48. U of each Y-axis and X-axis pulse motor via circuits 44 and 45
Rotation can be controlled by outputting P and DOWN pulses.

An algorithm for correcting the positional deviation in this control system will be described next. First, FIG. 11 is a flow chart for correcting the movement deviation of the control system of FIG. 10 in the vertical and horizontal directions (X-Y directions). The displacement in the vertical and horizontal directions is caused by the drift of the drive circuits mounted on the Y-axis and X-axis galvanometer mirrors 14 and 15. Regarding the procedure for correcting this displacement, the Y-axis and X-axis galvanometer mirrors 14 and 15 are moved and the position detector 13 is irradiated with the laser beam in the same manner as described in FIG. Draw a predetermined square trajectory. As a result, the digital data of four points q _{0 to} q ₃ of the irradiation position obtained through the four slits of the position detector 13 are used for the X-axis and Y-axis position detection circuit.
It is taken into CPU48 via 40 and 41. In the CPU 48, the calculation is performed using the equation (1), and the correction values Δx = p ₁ x, Δy =
By calculating p ₁ y and performing addition or subtraction with respect to the current value, the added or subtracted values δx, δy are used as subsequent correction values (bias values) to move point p ₁ to the center of the slit. The displacement deviation is corrected so that the center p ₀ of the beam square trajectory coincides with the slit center. Completion of the correction of this displacement is expressed by the equation (2) using Δx, Δy
It is determined by Δ ₁ (constant). Next, FIG. 12 (a) and FIG.
FIG. 12 (b) shows eight types of correction tables shown in FIG. 12 (a). This rotation deviation is the movement of the Y-axis and X-axis galvanometer mirrors 14 and 15 in the mirror axis direction, and the Y-axis and X-axis galvanometer mirrors 14 and 1 are moved.
It is caused by the drift of the mechanical system of 5. Regarding the procedure for correcting this rotation deviation, the Y-axis and X-axis galvanometer mirrors 14 and 15 are moved to irradiate a laser beam on the position detector 13 in the same manner as described in FIG. Draw a predetermined square trajectory. Thereby, the digital data of the irradiation position points r ₀ and r ₁ obtained through, for example, two slits in the vertical direction (Y-axis direction) of the position detector 13 are transmitted via the X-axis and Y-axis position detection circuits 40 and 41. Capture to CPU48. For CPU48 (3)
The value of the length l ₁ = r ₀ −r ₁ of the Y axis is calculated by using the formula and correction is performed. That is, as shown in FIG. 12 (b), the X axis, Y
The pulse generators 44, 45 to the axis pulse motor output a fixed number of up and down pulse combinations in sequence, each independently, and move the Y-axis and X-axis galvanometer mirrors 14 and 15 again to position them. Draw a square locus by laser beam irradiation on the detector 13 and draw the points r ₂ and r ₃ on the Y axis at that time by the CPU 48.
The value of Δ = (r ₂ −r ₃ ) −l ₁ is calculated and stored. When the correction of these eight combinations is completed, Δ0
Find the combination of the maximum types of correction effects that maximizes the
The up and down pulses with variable pulse number from 4,45 are output to perform correction, and the points r ₄ and r ₅ on the Y axis of the square locus of the laser beam on the position detector 13 are fetched into the CPU 48 again. Then, the value of Δ = (r ₄ −r ₃ ) −l ₂ is calculated, the rotation deviation θ _{0 is} sequentially corrected, and the correction is completed under the condition of ΔΔmin.

As described above, it is possible to correct the positional deviation of the laser beam irradiation in the vertical and horizontal directions and the rotational deviation due to the drift of the electric circuit system and the mechanical system of the optical axis controller 3 including the Y-axis and X-axis galvanometer mirrors 14 and 15. is there.

〔The invention's effect〕

As described above, according to the present invention, the distortion due to the positional deviation of the figure or the like written by the laser beam irradiation on the liquid crystal element of the liquid crystal projection type display is automatically corrected, and the line segment or the like written is corrected. Since it is possible to compensate for erasure during erasure, it is possible to achieve excellent display with high resolution and little distortion.

Further, since the position detection for the positional deviation correction is performed by the same laser beam as that for writing, the device configuration can be downsized.

[Brief description of drawings]

FIG. 1 is a block diagram of the overall structure showing an embodiment of a liquid crystal projection type writing position correcting device according to the present invention, and FIG. 2 is a basic diagram of a laser beam optical system including a position detector 13 according to the present invention shown in FIG. Configuration perspective view, FIG. 3 (a),
(B) and (c) are perspective views, plan views, laser beam irradiation plan views, and fourth views of the components of the position detector 13 shown in FIGS. 1 and 2.
FIG. 5 is an equivalent circuit diagram of the position sensor plate 16 of the position detector 13 shown in FIG. 3A, and FIG. 5 is a position detector 13 according to the present invention shown in FIG.
FIG. 6 is a block diagram of a basic configuration of a laser beam position correction control system including the above, FIG. 6 is a circuit block diagram of the position detection circuit 24 of FIG. 5, and FIGS. FIGS. 8A, 8B, and 8C are plan views for explaining the correction procedure of the lateral displacement, and FIGS. 8A, 8B, and 8C are plan views for explaining the correction procedure of the rotational deviation, and FIG. 9 is a liquid crystal projection according to the present invention. FIG. 10 is a block diagram showing the specific configuration of a laser beam optical system showing an embodiment of a writing position correction method for a display, FIG. 10 is a block diagram showing the specific configuration of the same laser beam control system, and FIG. Flow chart for correction of displacement in direction
12 (a) and 13 are the flowcharts for similarly correcting the rotational deviation, and FIG. 12 (b) is a diagram showing the eight kinds of correction tables in FIG. 12 (a). 1 ... Writing control unit, 2 ... Laser (oscillator), 3 ...
Optical axis controller, 4 ... Writing control circuit, 5 ... Liquid crystal element,
6 ... Projection optical unit, 7 ... Light source, 8 ... Lens, 9 ...
Half mirror, 10 …… Projection lens, 11 …… Screen,
12 …… Screen controller, 13 …… Position detector, 14
...... Y-axis galvanometer mirror, 15 …… X-axis galvanometer mirror, 16 …… position sensor plate, 17 …… laser beam shield plate with slits in the cross direction, 20,21 …… X-axis position detection output (terminal ), 22, 23 …… Y-axis position detection output (terminal), 24…
... Position detection circuit, 25 ... X-axis and Y-axis position information digital data, 37, 38 ... Stage, 40 ... X-axis position detection circuit, 4
1 …… Y-axis position detection circuit, 42,43 …… D / A converter, 44,45…
… Pulse generator, 46,47 …… Drive amplifier, 48 …… CP
U, 49 …… Memory.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Nagayama 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Ltd. Omika Plant, Ltd. (72) Ichiro Katsuyama 5-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 within Hiritsu Process Computer Engineering Co., Ltd. (56) Reference JP-A-51-114143 (JP, A) JP-A-54-58042 (JP, A) JP-A-55-67722 (JP, A) Kai 56-1018 (JP, A)

Claims (1)

[Claims] 1. A laser that generates a laser beam, an optical axis controller that controls the optical axis of the laser beam, a liquid crystal element whose transparency changes by irradiation of the laser beam whose optical axis is controlled, and the transparency. Of the liquid crystal element that changes the liquid crystal element, a projection lens that magnifies the light from the liquid crystal element that has given the projection light and projects it on the screen, and a writing device that controls the optical axis controller and the like. In a writing position correction device for a liquid crystal projection display comprising a control circuit and a screen controller for instructing control data to the writing control circuit, etc., the optical axis controller for detecting the irradiation position of the laser beam by a position detecting means. The position detecting means includes a slit shielding plate having slits in the X-axis and Y-axis cross directions, and a square on the slit shielding plate. A position detecting element for irradiating the laser beam so as to draw a locus and detecting the position of the laser beam that has passed through the slit, and a position detection output detected by the position detecting element for four-point digital in the X-axis and Y-axis directions. A position detecting circuit for converting into position information, and the correction control means of the optical axis controller performs a position correction correction calculation from the four-point digital position information from the position detecting circuit, and the center of the four points is the slit. Position correction command is output to the write control circuit of the optical axis controller so as to coincide with the intersection point of the optical axis controller to correct the positional deviation in the vertical and horizontal directions of the optical axis controller, and further the Y axis from the position detection circuit. A rotational misalignment correction command is output to the writing control circuit of the optical axis controller so that the rotational misalignment correction calculation is performed from the two-point digital position information in the direction to maximize the length between the two points in the Y-axis direction. Writing position correcting device for a liquid crystal projection type display, characterized in that it consists of the screen controller for correcting the rotational displacement of Kihikarijiku controller.