JP2002188941A - Liquid crystal display panel for position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display panel for a position detector having high resolution and high reliability. SOLUTION: This liquid crystal display panel 1 is constituted by facing a pair of glass substrates 2, holding the interval by a spacer 3, and enclosing liquid crystal 4 therein. An ITO film 5 is deposited on the glass substrate 2 to form a liquid crystal driving electrode, and the ITO film 5 is vapor deposited with the width of 10-100 μm at the pitch of 10-100 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a numerical control machine, a machine, a semiconductor substrate transfer device, a three-dimensional drawing device, an endoscopic surgery device, a μ machine manufacturing device, an articulated robot,
Gene therapy drug manufacturing device, position control non-contact shape measuring device,
The present invention relates to a position detection liquid crystal display panel used for position control of a drive system actuator such as an optical disk inspection device and a DNA inspection / analysis device.

[0002]

2. Description of the Related Art In recent years, demands for servo motors for semiconductor / liquid crystal production equipment, inspection equipment, inserters, mounters, machine tools and the like have been increasing. Furthermore, due to the improvement in precision, the application to injection molding machines and printing machines is expanding. On the other hand, a small servo mechanism for application to microfabrication / inspection technology of a micro factory, a small robot, and the like has been actively developed.

[0003] Generally, a high-precision servo mechanism is composed of a drive motor, a fine-motion decelerator, and a position detector. However, the position detector has a high weight in signal processing software, and the development of detection hardware is required. If a high-precision position detector is developed, extremely quick and precise driving by performing tracking measures, automatic focus adjustment, temperature drift compensation, and the like of a high-density optical disk drive becomes possible. In addition, due to the demand for quality inspection of high-density disk products, nano-order defect position precision detection equipment and roughness, outer and inner peripheral scratches,
Warping, application to the surface accuracy measurement device such as waviness can be expected greatly. In the future, in surface flaw detection, which is indispensable for high-speed production, the incremental detection method based on relative information from the encoder makes it difficult to identify the observation position, and suppresses errors only by software recognition. It is expected that it will not be possible. In this way, in the future of the position detector, high-resolution at the nanoscale and absolute position detection of the observation position are indispensable. Therefore, the study of element devices necessary for servo position detection has been started.

[0004] Most of the recent moving position detecting methods are an optical method and a magnetic method, each of which comprises a length measuring scale and a detecting pickup. The former is a method of detecting a change in transmission / reflection characteristics of light using an LED or LD, and the latter is a method of detecting magnetism from a magnetic material using a coil or the like. In order to realize high resolution, a method of generating a phase shift in a sensor signal by arranging a multi-element detector and multiplying the signal by a logic element or quantizing a detected analog signal has been conventionally used. In position detection on the order of nanometers, this method of multiplication is important, and it can be said that the cause of errors due to processing on software depends on the quality of its output. At present, the method which is said to have the highest detection resolution is an optical multiplication method, and the resolution is increased by quantizing an analog signal from a pickup. Incidentally, it falls short of optical there is temporal change in magnetic flux density when a magnetic method.

[0005]

However, optical position detection is generally affected by the disturbance of diffracted light, and the finer the patterning, the more adversely the interference of diffracted light due to transmission or reflection affects the length measurement accuracy. Has been unavoidable. In addition, the accuracy of multi-element arrangement is required in multiplication to increase the resolution, and the position-to-signal output characteristics from the pickup are not linear. A very large point remains as an issue. On the material side, the quality of the scale for length measurement, which is an element of the position detector,
In particular, consideration is given to heat and environmental temperature. For example, using micromachining technology or vapor deposition technology in the nanoscale manufacturing method enables the manufacture of a small precision scale, but it is difficult to provide a sufficient thickness, so it is easily deformed by delicate residual stress or thermal stress. Things
Sufficient reliability cannot be obtained due to dynamic deformation when driving at high speed. Therefore, the conventional optical detection has limitations in high resolution and high reliability, and a new scale material has been required.

It is ideal to have the absolute position sensing technology as described above. For this reason, conventionally, when producing a precision vapor deposition scale, a method of knowing by imprinting a code pattern for knowing an absolute position in the scale has been adopted, but it has been complicated, difficult to manufacture, and expensive. . Therefore, an object of the present invention is to provide an optimum material as a scale material for position detection by examining the material.

[0007]

SUMMARY OF THE INVENTION The present invention is characterized in that a liquid crystal display panel can add a characteristic to an arbitrary position by applying an electric field, and that components such as glass are robust and have little variation with respect to changes in ambient temperature. Focusing on the fact that the refractive index distribution can be easily and electrically controlled, the inventors studied a configuration for detecting the position of the liquid crystal display panel.

That is, according to the present invention, a plurality of pixels are arranged, the width of the pixels is 10 to 100 μm, and the pitch is 1
Provided is a liquid crystal display panel for a position detector having a thickness of 0 to 100 μm. Here, the pattern of the plurality of pixels is preferably staggered, but is not limited to this. The width of the pixel is 5
５００500 μm, preferably 20-100 μm. This is because when the thickness is 5 μm or less, the influence of interference of diffracted light cannot be ignored due to the Fraunhofer law, as in the case of the diffraction grating, and this becomes disturbance light, and a precise position cannot be specified. On the other hand, if it is wider than 500 μm, the characteristic of the linearity of the movement position versus the output will be distorted. Further, the pitch is 5 to 500 μm, preferably 20 to 100 μm
It is. This is for the same reason as the pixel width described above.

More specifically, the present invention relates to a liquid crystal display panel for a position detector comprising a pair of transparent substrates opposed to each other and sealing a liquid crystal therebetween, wherein a transparent electrode film is provided on one side of the transparent substrate. With a width of 5 to 500 μm and 5 to 500 μm
For position detectors, the same transparent electrode film is deposited on the opposing transparent substrate in pairs with one side, and a light-shielding film is short-circuited around the transparent electrode film. Provide a liquid crystal display panel. The reason why the width and the pitch are limited to the above values is the same as described above.

Here, the transparent substrate is, for example, a glass substrate,
Examples include, but are not limited to, polyacrylic substrates. Further, as the transparent electrode film, for example, it is preferable to use an ITO film, but it is not limited to this. The transparent electrode film is deposited by a CVD method or the like. Further, the liquid crystal includes, for example, a birefringent liquid crystal element, a transmission scattering liquid crystal element, a TN (twisted nematic) liquid crystal, an STN (super TN) liquid crystal, a ferroelectric liquid crystal element, an antiferroelectric liquid crystal, and a polymer dispersed liquid crystal. , But is not limited thereto. The distance (cell gap) between the opposing substrates is 1 to 100 μm, preferably 5 to 20 μm. Further, as the light-shielding film, for example, an aluminum vapor-deposited film can be used, but the material is not limited as long as it can prevent the wraparound of light. The transparent substrate on which the light-shielding film is formed is preferably on the light-receiving side of the optical means described later.

When the cell gap of the liquid crystal display panel is 5 to 20 μm, the voltage applied to the transparent electrode is
kHz, preferably 100 to 700 Hz, 5 to 50
It is preferable to apply a rectangular wave of V, preferably 10 to 25 V. By changing the drive voltage within this range, the height and / or width of the signal waveform can be adjusted. This is because the adjustment of the driving voltage of the liquid crystal makes it possible to adjust the distribution of the refractive index of the liquid crystal. 1) Adjustment of lens NA (Numerical Apercha numerical aperture): When a voltage is applied, the effect of the lens is produced by the alignment of the liquid crystal. However, the voltage adjustment allows the focus function to be adjusted. Can be used as 2) Improvement of detection SN: The higher the applied voltage, the higher the peak value of the signal, and the higher the SN. 3) Point detection becomes possible based on the difference in peak value. That is, it is possible to arbitrarily specify the absolute position of the moving distance. The driving voltage of the liquid crystal may be changed independently for each pixel or may be changed collectively as a set of a plurality of pixels. However, when performing point detection, the driving voltage is changed independently for each pixel. Is preferred.

The change in the pixel of the liquid crystal is read by optical means. The optical means includes a light projector for irradiating the liquid crystal display panel with light, and a light receiver for detecting transmitted and scattered light from the liquid crystal display panel. Examples of the light emitter include, but are not limited to, a light emitting diode, a laser, a lamp, and EL (electroluminescence). The wavelength region to be used may be in the ultraviolet to infrared region, preferably in the wavelength region of 300 to 1500 nm. Further, the light projector may be a point light source or a light source for irradiating the entire surface of the liquid crystal panel with a backlight.

As the light receiver, various infrared sensors such as a photodiode, a photomultiplier, a solid-state light receiving sensor, a pyroelectric sensor, and a thermopile can be used. In addition, the light emitter and the light receiver may be integrated as a photocoupler or a photointerrupter. Further, the transmitter and the receiver are provided with a plurality of photointerrupters, PSD (posision s).
a plurality of devices such as an ensing device). In addition, the case where the light projector is a single point or surface light source and only a plurality of light receivers are connected in series, and the reverse case is also included.

Further, a slit may be provided between the light projector and the liquid crystal display panel or between the liquid crystal display panel and the light receiver to prevent light from entering. The slit width differs depending on the size of the liquid crystal pixel, but for example, in the case of a scale,
It is 50 to 500 μm. Further, a scanning means for scanning the optical means along the surface of the liquid crystal display panel may be provided. Examples of the scanning unit of the light projector include a device in which a mirror is provided between the projector and the liquid crystal panel and light is distributed by scanning the mirror, and a device in which the projector itself is placed on a mounting table and the mounting table is moved. However, the present invention is not limited to these. When the mounting table is moved, it is moved by a linear motor, a screw feed mechanism, a rack and pinion mechanism, or the like. Similarly, the scanning means of the light receiver includes both a means for providing a condensing mirror between the liquid crystal panel and the light receiver to perform mirror scanning and a means for moving the light receiver itself. The scanning direction is not limited to one direction of the liquid crystal panel, and may be any of the XY direction and the zigzag scanning direction.

The liquid crystal display panel for a position detector according to the present invention can be used for any position detection such as position control of a drive system actuator. Examples of the drive system actuator include, but are not limited to, a motor, a solenoid, a cylinder, and a spring. Further, as the motor, for example, a servo motor can be used, but it is not limited to this.

[0016]

Embodiments of the present invention will be described with reference to the drawings. 1A and 1B are schematic views of a length measuring device using the liquid crystal display panel of the present invention. FIG. 1A is a top view, FIG. 1B is a side view, FIG. 1C is an enlarged top view of the liquid crystal display panel, and FIG. It is a liquid crystal display panel side view. In FIG. 1, reference numeral 1 denotes a liquid crystal display panel. The liquid crystal display panel 1 has a pair of glass substrates 2 opposed to each other, is held at a distance (for example, 5 μm) by a spacer 3, and has a liquid crystal 4 sealed therein. In addition, an ITO film 5 is deposited on the glass substrate 2 to form a liquid crystal drive electrode.
A voltage controlled by a control circuit (not shown) is applied to the liquid crystal drive electrode. On one side of the glass substrate 2, a pattern for forming a 30 μ square light transmission window by the ITO film 5 is formed at a pitch of 30 μm (FIG. 1C), and a similar ITO film 5 is formed on the opposing glass substrate 2. Is formed in such a manner as to form a pair with one side, and a light-shielding aluminum vapor-deposited film 6 is short-circuited around the ITO film 5. The liquid crystal 4 is, for example, a TN (twisted nematic) liquid crystal.

On both sides of the liquid crystal display panel 1, detectors comprising an LED 7 and a photodiode (PD) 8 are provided. As shown in FIG. 1 (b), the PD 8 is accommodated in a depression of a U-shaped alumina substrate 9 and the liquid crystal display panel 1 is arranged at a step.

The aperture diameter between the LED 7 and the liquid crystal display panel 1
An aperture 10 having a diameter of 100 μm is provided, and the clearance thereof is set to 1 μm using an alumina substrate 9.
The wavelength of the LED 7 used as a light source is, for example, 860 nm and the driving frequency is 60 kHz. The light flux passes through the aperture 10 and enters the liquid crystal display panel 1, and then the PD 8 receives light emitted from the liquid crystal display panel 1 again. The liquid crystal display panel 1 is connected to the motor 11 and is moved along the step of the alumina substrate 9 at a constant speed of 1 mm / sec.
The DC signal output from the PD is amplified by the amplifier 12, and then sent to a signal processing circuit (not shown).

With the above configuration, a voltage was simultaneously applied to each ITO pattern, and the reproducibility of the light beam emitted from the liquid crystal length measuring device was evaluated. For comparison, the same evaluation was performed for a case where only the vapor-deposited glass substrate was used and a case where no electric field was applied to the liquid crystal panel. During the measurement, pulses of 12 to 15 V and 500 Hz having opposite phases were applied to both ends of the liquid crystal. The dependence of the detection signal characteristics on the driving of the liquid crystal was examined by changing the driving voltage of the liquid crystal.

FIG. 2 shows the experimental results. 2A and 2B are diagrams showing traces of a pickup signal. FIG. 2A shows a case where only a glass substrate with a vapor deposition film is used, FIG. 2B shows a case where an electric field is not applied to a liquid crystal panel, and FIG.
(D) shows output characteristics obtained in the case of applying an electric field of 12 V pulse. As shown in FIGS. 2A and 2B, the pickup output is usually distorted in a lattice plate or a liquid crystal display panel, but when the liquid crystal is driven, a moving position pair having good linearity according to the window width and interval is used. The signal strength was obtained, and it was found that the signal was an ideal analog detection signal. This indicates that the position can be detected with high sensitivity by quantization.
This suggests that an extremely high resolution of about 4 digits can be realized. Good results were also obtained in the reproducibility of the signal waveform between the liquid crystal windows. At that time, as shown in FIGS. 2C and 2D, it was found that the height / width of the waveform could be easily adjusted by changing the drive voltage. If a different point is used between the case where an electric field is applied to the liquid crystal display panel and the case where it is not applied, it is possible to drive each liquid crystal pattern independently and set a threshold voltage for signal discrimination and compare pulse width change and signal strength. Indicates that an arbitrary position can be recognized. In this way, the ideal characteristics as a high-speed length measuring device can be read from the pickup from the liquid crystal display panel. These results suggest that the arrangement of the liquid crystal molecules changes with respect to the driving pulse, and that the emitted light beam is optically adjusted by forming a steady refractive index distribution. As a factor other than the driving pulse condition, it is considered that each window of 30 μm square of the liquid crystal display panel of the present invention is in a liquid crystal arrangement according to an electric field generated in a state where the counter electrode surface is shared.

FIG. 3 shows an application example of a liquid crystal length measuring device using the liquid crystal electro-optic effect to an absolute type servo mechanism. In FIG. 3, reference numeral 31 denotes a measuring unit, and the measuring length unit 31 includes a liquid crystal display panel 33 and the liquid crystal display panel 3.
3 comprises an LED 32 and a PD 34 arranged on both sides. The measurement length unit 31 moves with the driving of the motor 41.

The liquid crystal display panel 33 comprises a pair of glass substrates opposed to each other, as shown in FIG. 1, spaced from each other by a spacer (for example, 5 μm), and sealed with liquid crystal. Is deposited to form a liquid crystal drive electrode. The liquid crystal crystal driving electrodes are driven by a liquid crystal driving driver 35, and the liquid crystal driving driver 35 is controlled by a CPU 36. The 30 μ square patterns are alternately arranged on the liquid crystal display panel 33, and an address is added to each position, and the address is stored in the CPU 36.

An amplifier 37 amplifies the signal of the PD 34, a position control unit 38 for storing a starting position,
39 is a control unit for controlling the motor 41, and 40 is a servo driver for driving the motor. The motor 41
Is connected to an object (not shown).

In the apparatus shown in FIG. 3, the absolute position can be recognized by arbitrarily changing the pattern in the length measuring unit by driving the liquid crystal. In the absolute position detection, first, the liquid crystal drive driver 35 is driven by a signal from the CPU 36 to drive the liquid crystal display panel 33 by predetermined patterning. By storing the starting point in the position control unit 38 and then driving the liquid crystal pattern of a necessary address, it is possible to distinguish the grid from other grids. Thus, the absolute position can be detected without imprinting a complicated absolute pattern. In addition, by storing the starting point, when the power is turned on again, the same position is displayed by driving the liquid crystal, so that an object (not shown) can always be moved from the same position. With the configuration of FIG. 3, it is possible to realize a very simple and high-performance absolute encoder capable of reducing the load of software signal processing, shortening maintenance time and starting time, and moving at high speed.

In the above description, only the length measurement has been described. However, the fact that the refractive index can be controlled can be sufficiently applied to the detection of precise displacement such as the depth and warpage of an object. Therefore, “position detection” in the present invention refers to a broad concept including displacement detection.

[0026]

When the liquid crystal display panel of the present invention is used, characteristics can be added to an arbitrary position by applying an electric field, components such as glass are robust, and there is little variation with changes in ambient temperature. The distribution of the rate can be easily and electrically controlled. Furthermore, in the present invention, as described above, 1) adjustment of the lens NA 2) improvement of the detection SN 3) point detection becomes possible from the difference in the peak value.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a length measuring device using a liquid crystal display panel of the present invention.

[2] output characteristic diagram during pickup scanning on the liquid crystal window.

FIG. 3 is a configuration diagram of an absolute servo.

[Explanation of symbols]

 1: liquid crystal display panel 2: glass substrate 4: liquid crystal 5: ITO film 7: LED 8: photodiode

Continued on the front page F-term (reference) 2F065 AA02 AA06 BB02 BB18 DD04 FF02 GG06 GG07 GG12 GG22 GG24 HH13 HH15 JJ01 JJ17 JJ18 KK01 LL28 LL41 LL50 MM07 NN08 PP02 PP22 UU08 2F103 EB12 CA12 EB07 EB07 EB33 ED01 ED11 FA08 2H088 EA52 EA55 GA10 HA02 HA06 HA14 HA28 JA05 JA09 JA13 JA17 JA20 KA01 MA20 2H092 GA04 GA13 GA15 GA21 HA04 NA25 PA06 PA09 PA13 QA07 QA09 QA10 QA13 QA14 QA15 RA10

Claims (4)

[Claims] 1. A method according to claim 1, wherein a plurality of pixels are arranged, and the width of the pixels is 5 to 5.
A liquid crystal display panel for a position detector having a size of 00 μm and a pitch of 5 to 500 μm. 2. A liquid crystal display panel for a position detector comprising a pair of transparent substrates opposed to each other and sealing liquid crystal between them, wherein a transparent electrode film having a thickness of 5 to 500 μm is formed on one side of said transparent substrate.
In the width, and with deposited at a pitch of 5 to 500 [mu] m, the transparent substrate opposing deposited in the form of forming a one-sided paired similar transparent electrode film, and by short-circuiting the light-shielding film around the transparent electrode film Liquid crystal display panel for position detector formed. 3. The method according to claim 1, wherein the transparent substrate is a glass substrate and the transparent electrode film is I
3. The liquid crystal display panel for a position detector according to claim 2, which is a TO film. 4. A liquid crystal comprising a birefringent liquid crystal element, a transmission scattering liquid crystal element, a TN (twisted nematic) liquid crystal, an STN (super TN) liquid crystal, a ferroelectric liquid crystal element, an anti-ferroelectric liquid crystal,
3. The liquid crystal display panel for a position detector according to claim 1, which is a polymer dispersed liquid crystal.