JPH02118511A - Scanner and display device constituted by using this scanner - Google Patents

Abstract

PURPOSE:To improve the stability and reliability of the device by using voice coil motors in place of a galvanomirror by driving scanning mirrors the voice coil motors in accordance with the output of encoders. CONSTITUTION:An X-axis mirror 20 and Y-axis mirror 21 which bend the direction of the light from a semiconductor laser 1 are driven by using the voice coil motors (VCM) 24, 25 and the shaft encoders 22, 23 which monitor moving quantity. Encoder pulses 26 generated by the encoders 22, 23 are inputted to a scanner control section 28 and the VCMs 24, 25 are driven by the VCM control signal from a control section 28. Since the scanning mirrors 20, 21 are driven always by the moving quantity corresponding to the external signals at all times, the safety and reliability are improved by using the VCMs having durability in function in place of the galvanimirror which requires delicate adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a scanning device and a display device using the scanning device, and in particular to a device for writing information to a liquid crystal display element using a laser beam and using the liquid crystal display element. The present invention relates to a scanning device suitable for an enlarged projection system and a display device using the scanning device.

(Prior art) Magnifying projection type display devices using liquid crystals generally transmit information from the back side to the liquid crystal element on 2F using a laser beam using human power.
Information is displayed by projecting light onto the liquid crystal element from the i-near f plane and projecting the reflected light onto a screen. Third
The figure is a schematic diagram of a conventional method of aging the liquid crystal element f. In the figure, a laser beam 12 emitted from a semiconductor laser 1 is aligned in beam shape by a collimating lens 2 and enters a scanning system. The scanning system is constituted by an X-axis circumferential carbanomirror 3 and a yIIIli carbanomirror 4, and is controlled in two axes. The beam scanned by the scanning system is focused onto the liquid crystal element f6 by the writing lens 5, and vector scanning is performed in accordance with human input information. A smectic type liquid crystal element is usually used. Smectic type liquid crystals are transparent under normal conditions without being heated. When the liquid crystal in this state is hit by the focused laser beam 12, the liquid crystal is heated and becomes a liquid state, and when it cools down, the molecular arrangement becomes disordered and light is scattered. As a result, the portion written with the laser beam can be observed on the liquid crystal element 6.

FIG. 4 shows a schematic diagram of an optical system for projecting information written on the liquid crystal element 6. Light from a projection light source 8 such as a xenon lamp is condensed by a condenser lens 9, and then reflected by a mirror 1.
0 and a projection optical system 11a. Information is displayed on the LCD 6 depending on the method of sailing speed,
Depending on this state, the reflected light returns to the projection optical system 11a. The projection optical system 11a uses a mirror 10 for inputting the reflected light flux.
Its role is to guide the light so that it is focused in a position that avoids the mirror 10
The light flux that has passed through is projected onto the screen by the projection optical system 11b.

The above is the general principle of a system using a liquid crystal display element. An example of this in color is shown in FIG. For colorization, the optical system is basically prepared with three systems for the three colors R, G, and B, and color display is performed by combining these systems. 1 in the figure is a semiconductor laser light source, which is turned on independently for the R channel, G channel, and B channel.
It is equipped with a semiconductor laser that is turned off. Reference numeral 13 denotes an optical scanning system that scans the light coming from each light source, and conventionally, a carbano mirror is used as described above. Reference numeral 14 denotes a laser beam splitter for distributing the light emitted from the optical scanning system to the R, G, and B channels of the liquid crystal display device. 14-1.14-2
．． Reference numeral 14-3 represents a light splitter composed of a mirror and a beam splitter, and serves to guide light from each light source to each corresponding liquid crystal display element 6.

The above is the structure of the write system, and in the read system, RGB system synthesis is now attempted.

What differs from the configuration shown in FIG. 4 is the 15 composite system composed of a group of dichroic mirrors.

15-1.15-2 and 15-3 are B, G, H respectively
It is a dichroic mirror or mirror corresponding to the above, and has the roles of distributing incident illumination light and combining reflected light. Other operations are the same as in FIG. 4.

Incidentally, in the configuration of FIG. 5 for both the write system and the read system, R
It is necessary to insert an optical path length correction member in order to correct the difference in optical path length between each optical system leading to GB. However, in order to simplify the figure, it is omitted in the figure.

(Problems to be Solved by the Invention) As can be seen from the examples explained above, in the conventional liquid crystal enlarged projection type display device, the writing optical system shown in Fig. Galvano mirrors that require careful adjustment
is used.

The readout system shown in FIG. 4 is a fixed optical system and can be said to be a stable system.

Therefore, in order to configure the entire device as a stable system,
A stable scanning device that does not require adjustment to replace the galvanometer mirror in the writing optical system is indispensable.

However, until now, there has been almost no scanning device that can practically replace the galvanometer mirror in terms of simplicity, operability, and efficiency.

In view of the above points, it is an object of the present invention to provide a scanning device constructed from members that replace the conventional Calhano mirror, and a display device using the scanning device.

(Means for Solving the Problems) Therefore, in the present invention, as an alternative system to the carbano mirror, a whirlpool coil motor is used as a driving means for driving the mirror, and an encoder for monitoring the amount of movement of the mirror is used. and a control unit that performs feedback control so as to obtain a stable movement amount in accordance with the signal from the encoder, and the scanning device is configured, and the scanning device is used to configure a display device. do. As a result, the scanning device and display device of the present invention can always drive the mirror by the amount of movement corresponding to the external number 43, making it possible to realize stable and highly accurate driving.

(Embodiment) FIG. 1 is a schematic diagram of a writing optical system constructed based on an embodiment of a display device using the scanning device of the present invention. In the figure, light emitted from a semiconductor laser 1 is aligned in shape by a collimator lens 2, and then deflected by an X-axis mirror 20 and a Y@mirror 21. The light then passes through the writing lens 5 and is imaged at a predetermined position on the liquid crystal display element 6. The structure is the same as that shown in FIG.

The embodiment shown in FIG. 1 differs from the structure shown in FIG. 3 in the structure of the mirror scanning section.

In other words, the rotation angle of the X-axis mirror is determined by the X-axis voice coil motor (
This is determined by the movement of the VCM 24 (hereinafter abbreviated as VCM). The VCM 24 is controlled by an X-axis peripheral shaft encoder 22 set at the rotation center axis of the X-axis mirror 20.
The encoder pulse 26 generated by the scanner controller 28
This is done by providing feedback to Control unit 28
generates a VCM control signal 27 in accordance with the signal of the encoder pulse 26 to drive the VCM 24, and the X-axis mirror is driven to a predetermined angle.

The rotation angle control of the Y-axis mirror 21 is also performed using a similar system configuration.

By controlling the rotation angles of the X-axis mirror 20 and the Y-axis mirror 21 in this way, it becomes possible to draw two-dimensionally on the liquid crystal element 6 with a laser beam.

On the other hand, control of the X-axis and Y-axis mirrors is performed by the scanner control section 28. In addition, instructions for the amount of mirror movement itself, start,
Instructions for stop control and instruction signals for turning on and off the semi-moving body laser are performed by the control section 29 of the main body of the enlarged projection type display device. Depending on how the two mirrors are driven at this time, either vector scanning or rask scanning can be arbitrarily selected.

FIG. 2 is a detailed diagram of a mirror drive section of an embodiment of the scanning device of the present invention. The mirrors 20 and 21 are configured to reciprocate in an arc shape around a rotating shaft 32, and the back surfaces of the mirrors 20 and 21 and the VCMs 24 and 25
connected with. The operation of the VCM itself follows the well-known Fleminck's left hand rule. In other words, the strength of the magnetic field is B
(Wb/m2), the length of the coil, f2 (m),
: If the current flowing through the film is I (A), the generated thrust F (N) is expressed as F=Bffil, causing the VCM to move linearly.

This movement of the VCM is converted into an arc movement of the mirror.

Since the electric current mI flowing through the coil and the thrust force F are proportional, and the coil resistance is constant in a short time, it can be considered that the thrust force F is substantially proportional to the voltage V applied to the coil. Since the current is actually energized for a short time, it is possible to adjust the thrust by adjusting the voltage.

FIG. 6 is a graph showing the relationship between the applied voltage of the VCM and the amount of movement. As shown in the figure, VCM has hysteresis and therefore has poor edge-turning accuracy, and high accuracy cannot be obtained when used in an oven loop. For this reason, in the present invention,
It is equipped with a shaft encoder that monitors the amount of mirror movement to correct hysteresis and obtain high repeatability, and is characterized by -p that performs control.

FIG. 7 is an example of a functional block diagram of the scanner control section 28.

The control section 29 of the main body sends digital data regarding the amount of movement of the mirror to the scanner control section 28. Scanner control unit 28
In this case, a reference table 33 of movement amounts and applied voltages is provided in advance, and the applied voltage of the VCM is read out according to the values of the reference table 33.

Then, the read voltage value is converted into analog data by the D/A converter 34 and becomes the applied voltage of the VCM by the voltage generator 35 to drive the VCM.

The movement of the VCM driven according to such a procedure is converted into the rotational movement of the mirror as described above. However, due to the hysteresis of the VCM movement itself, the amount of rotational movement of the mirror is often different from the command value given by the control unit 29 of the main body at this point.

This error is monitored by an encoder (22 or 23) installed coaxially with the mirror drive shaft 32. The amount of movement of the mirror is determined by the counter 36 as an output pulse of the encoder.
detected. The value of the counter 36 and the VCM set data from the main body control section 29 are manually input to a calculator 37 and compared, and if the two differ, the calculated diameter correction data 38 is sent to the reference table 33 again.

The signal entered in the reference table 33 is exchanged with the correction drive applied voltage of the VCM through the same process as described above, and the mirror movement amount is corrected. By adding the above feedback process to the scanning process, highly accurate mirror position control was possible.

It should be noted that various modifications can be considered to the configuration of the scanner control section 28, such as providing a D/A conversion function in the voltage generation section 35 and directly generating the voltage applied to the VCM using digital data from the reference table 33. It will be done.

FIG. 8 is a schematic diagram of a main part of a second embodiment of the present invention. In the first embodiment, the mirror was rotated in both forward and reverse directions by changing the direction of the current, that is, the direction in which the voltage was applied, whereas in this case, the driving direction by the VCM was always limited to one direction. be. Driving the mirror in the opposite direction, that is, returning the mirror, is performed mechanically by an elastic member 39, such as a sublink, provided on the mirror. When the applied voltage of VCM is turned off, VCM
The driving force disappears, and the mirror returns to the predetermined position by the elastic member 39. By being able to concentrate on feeding in only one direction, the impact of mechanical backlash can be avoided, and V
The influence of hysteresis of the CM itself is reduced. As a result, the encoder only needs to perform pure position control of the VCM, and the processing load for hysteresis is lightened, making control easier. Furthermore, although the feedback control of the mirror position shown in FIG. 7 has a large relationship with the data transfer rate from the main body control section 29, it is also highly effective in speeding up the process by reducing the processing load.

(Effects of the Invention) As explained above, the present invention uses a functionally durable VCM in place of the galvano-mirror drive system, which conventionally had the biggest problem in terms of stability. We succeeded in improving stability and reliability.

Furthermore, the problem of VCM, which is poor edge reproducibility caused by hysteresis, has been solved by feedback control using an encoder monitor. As a result, the achievement of a scanning device and a display device using the scanning device that enables both rask scanning and vector scanning, and also improves linearity due to improved scan position controllability and improves image quality. is possible.

[Brief explanation of the drawing]

'fJ1 is an overall view of a liquid crystal enlarged projection type display device according to the present invention, FIG. 2 is a detailed view of an embodiment of the scanning section of the display device according to the present invention, and FIG. 3 is a diagram of a conventional display device. Optical system, FIG. 4 is a projection optical system of a conventional display device, FIG. 5 is a block diagram of a conventional color display device, and FIG. 6 is a V
A characteristic diagram of CM, FIG. 7 is a block diagram of an embodiment of a control section of a display device according to the present invention, and FIG. 8 is a schematic diagram of a seventh embodiment of a display device according to the present invention. In the figure, 1 is a semiconductor laser, 5 is an IJ lens, 6 is a liquid crystal element R-120, 21 is a scanning mirror 22, 23 is a shaft encoder, 24.25 is a whirlpool coil motor, 2
8 is a scanner control unit, 29 is a main body control unit, 30 is a bottle,
32 is a shaft, and 39 is a sublink.

Claims (2)

[Claims] (1) It has a voice coil drive means for driving the scanning mirror, an encoder that detects the amount of drive of the scanning mirror, and a control section that controls the voice coil drive means based on the output of the encoder. A scanning device characterized by: (2) In a display device that forms an image by scanning a predetermined surface with a laser beam, the display device includes a scanning mirror, voice coil driving means for driving the scanning mirror, and detecting the amount of drive of the scanning mirror. A display device comprising an encoder and a control section that controls the voice coil drive means based on the output of the encoder.