JP2002090704A - Read device for liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optically realize linearization of a relation between a distance and a sensor signal by suppressing diffraction (sneak path) of light. SOLUTION: When a rectangular wave pulse is applied to liquid crystal driving electrodes 5, 6, a liquid crystal 9 gets to a state in which molecules existing in periphery part rise with director angle distribution corresponding to field intensity distribution characteristics and light of LED(light emitting diode) 2 is collimated. Consequently a phototransistor 3 and a slit 4 are removed in a state of applying voltage to the liquid crystal driving electrodes 5, 6 and the light of LED 2 is received with the phototransistor 3 through the slit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a liquid crystal display panel reading device for reading pixels of a liquid crystal display panel. The reading device of the present invention includes, for example, a numerical control machine, a machine, a semiconductor substrate transfer device, a three-dimensional drawing device, an endoscopic surgery device, μ
It is applied to read liquid crystal scales for controlling the position of drive system actuators such as machine manufacturing devices, articulated robots, gene therapy drug manufacturing devices, position control non-contact shape measurement devices, optical disk inspection devices, and DNA inspection / analysis devices.

[0002]

2. Description of the Related Art For example, in a numerical control (NC) machine tool, a rotary force from a rotary drive source such as a servomotor is converted into a linear motion by a feed mechanism such as a rack and pinion mechanism, and a table or a tool is moved to a predetermined position. Moved to the position. In the case of this device, position control of a table or the like is performed by attaching a rotational position detector such as a rotary encoder to a servo motor that drives a control target, and feeding back the amount of rotation detected from this position detector to the servo motor or the like, The position of a control target such as a table is controlled by controlling the rotation amount of the servomotor.

In some cases, a linear encoder that detects displacement of linear motion is used instead of a rotary encoder. As a linear encoder, for example, the optical reading device is moved in synchronization with the drive of the servo motor on the optical scale, and the value of the scale is read by the reading device.
There is a so-called optical type. Here, as an optical reading device, there is an optical reading device that irradiates, for example, light from a light source to a scale and detects transmitted light and reflected light through a slit.

[0004]

In general, an object of an optical scale is to transmit or reflect light from a light source in a certain direction to sharpen the outline of the scale and to transmit the information to a light receiving device. However, in general, a light beam that has passed through a slit is diffused after passing by a diffraction phenomenon. For this reason, it is necessary to take measures to suppress the nth-order diffracted light in consideration of the slit interval and the light source wavelength. That is, not only does the problem not be solved even if the incident light is made parallel, but also the post-processing of the outgoing light must be precisely collimated by optical components. That is, if a space is provided between the optical component and the slit, more precise molding and more precise arrangement in consideration of aberrations and the like are required.

As a countermeasure, it is ideal to place a collimating lens on the slit or to incorporate the collimating lens in the slit before exiting from the slit. To achieve this, the scale itself must also have a lens function. Generally, a hologram element is generally considered as a method of giving a lens function to a scale, but it is difficult to perform patterning with a lens effect using a hologram element. Particularly, in terms of scale specifications, it has been considered that it is very costly to manufacture it in a material that suppresses thermal expansion that is indispensable, that is, a glass material.
Therefore, an object of the present invention is to provide a novel device that suppresses the diffraction of light that cannot be eliminated by the conventional method.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have noticed that liquid crystal molecules can easily adjust the refractive index distribution in a pixel or a pattern by an external force such as an electric field or a magnetic field. As a result of examining the driving method and other conditions in addition to the initial settings such as the wavelength used and the cell gap, the transient refractive index distribution control allows direct addition of the lens effect to the liquid crystal itself, thereby eliminating light wraparound. Thus, a parallel light beam was emitted from the pixels of the liquid crystal display panel. In addition, the liquid crystal display panel has a structurally common lens layer and has the ability to minimize the refractive index distribution between each pattern, which proved to be an ideal material for scale. .

That is, the present invention provides a liquid crystal display panel composed of a plurality of pixels, a liquid crystal drive section that applies a voltage to the liquid crystal display panel to cause a lens action, and a projector that irradiates the liquid crystal display panel with light. Provided is a liquid crystal display panel reading device including a light receiver for receiving transmitted / scattered light of light applied to a liquid crystal panel.

[0008] Here, the liquid crystal display panel is constructed by sealing liquid crystal between a pair of electrode plates. Each electrode plate is usually
For example, an ITO film, which can function as an electrode, is formed on a glass substrate by vapor deposition. The liquid crystal is, for example, any of 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. Cell gap (distance between a pair of electrode plates) is 1 to 100 μm.
m, preferably 5 to 20 μm.

The liquid crystal display panel has different pixels (patterns) depending on the application. For example, when used as a scale, it is preferable to display a binary code such as a binary code or a gray code. Here, the binary code means a scale composed of white pixels and black pixels (in terms of signal processing, only a signal of 0 or 1 in a binary system). The Gray code means a code in which a coding pattern always changes by only one bit and has very few optical malfunctions. In particular, the emitted, transmitted or reflected light from the smallest encoded pattern is transferred to the optical sensor while moving, and a signal corresponding to the amount of light is obtained. Alternatively, it can be known by quantization. The size of the liquid crystal pixel varies depending on the application, but when used as a scale, for example, 5 to 100
μm.

[0010] "Producing a lens effect" refers to a function of converging incident light when the orientation angle of liquid crystal molecules of a liquid crystal display panel becomes 1 to 45 degrees. Such a lens action depends on the type of liquid crystal and the wavelength used, but when the cell gap of the liquid crystal display panel is 1 to 100 μm, preferably 5 to 20 μm, the frequency is 10 to 10000 (10K) Hz, preferably 200 to 100 μm. At 2000 Hz, 3 to 18 V, preferably 5
This can be achieved by applying a rectangular wave of １５15 V. The duty ratio is preferably 50%, but is preferably 55 to 75%.
But it is possible. Note that the present invention is not limited to such conditions, and all conditions for “causing a lens action” apply.

As the light projector, for example, a light emitting diode,
Laser, lamp, EL (electroluminescence)
And the like, but are not limited thereto.
The wavelength range used is in the ultraviolet to infrared range, preferably 300
Those having a wavelength range of up to 1000 nm can be used. Further, the light projector may be a point light source or a light source for irradiating the entire 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. In the present invention, a scanning unit for scanning the optical unit along the surface of the liquid crystal display panel may be provided. Examples of the scanning means of the light projector include a method in which a mirror is provided between the light projector and the liquid crystal panel and light is distributed by scanning the mirror, and a method in which the light projector itself is placed on a mounting table and the mounting table is moved. However, the present invention is not limited to these. When moving the mounting table, a linear motor,
Move by screw feed mechanism, rack and pinion mechanism, etc. Similarly, the scanning means of the light receiver is provided with a condenser mirror between the liquid crystal panel and the light receiver to perform mirror scanning.
Any of those that move the light receiver itself is included. 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 reading device of the present invention can be used, for example, for reading a linear scale used for a drive system actuator. Examples of the drive system actuator include, but are not limited to, a motor, a solenoid, a cylinder, a spring, and the like. Further, as the motor, for example, a servo motor can be used, but it is not limited to this.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a liquid crystal display panel reading device of the present invention. In FIG. 1, reference numeral 7 denotes a liquid crystal display panel. In the liquid crystal display panel 7, a pair of glass substrates 8 are opposed to each other, and the gap is maintained by a spacer (not shown).
Is enclosed. Liquid crystal drive electrodes 5 and 6 are formed on the glass substrate 8 by depositing an ITO film. In addition,
The cell gap is, for example, 5 μm, and the liquid crystal drive electrodes 5, 6
Has a width of 30 μm.
Further, as the liquid crystal 9, for example, TN (twisted nematic) or STN (super twisted nematic) is used. The oscillator 1 is connected to the liquid crystal drive electrodes 5 and 6, and a pulse voltage of a predetermined frequency (50 to 500 Hz) is applied. The applied voltage is, for example, 12V. Reference numeral 10 denotes a logic circuit.

Reference numeral 2 denotes an LED which emits light having a wavelength of, for example, 860 nm. Although the LED 2 is illustrated as irradiating only the pixel portion of the liquid crystal display panel 7 in the drawing, the entire surface of the panel 7 is illuminated. Reference numeral 3 denotes a phototransistor that receives light from the LED 2. Light received by the phototransistor 3 is integrated by the capacitor 12 to obtain a DC output. Note that 11 is a resistor, and 13 is an amplifier. Reference numeral 4 denotes a slit, and the slit width is 50 to 1 when the width of the liquid crystal pixel is 30 μm.
00 μm is desirable. The slit 4 and the phototransistor 3 move integrally along the surface of the liquid crystal display panel 7 (in the direction of the arrow in the figure). Although not shown, a linear motor is used as the moving means.

With the above configuration, the principle of the present invention is as follows. When no voltage is applied to the liquid crystal driving electrodes 5 and 6, the liquid crystals 9 are horizontally arranged as shown in FIG. In this state, the light of LED2 is diffracted due to the phenomenon of diffraction.
Does not pass through slit 4. However, the liquid crystal drive electrodes 5, 6
Is applied with a rectangular wave as shown in FIG. In FIG. 3, A indicates a driving pulse to the liquid crystal driving electrode 5, and B indicates a driving pulse to the liquid crystal driving electrode 6. When a rectangular wave as shown in FIG. 3 is applied to the liquid crystal drive electrodes 5 and 6, as shown in FIG.
Is in a state in which the surrounding molecules stand by the orientation angle distribution according to the electric field intensity distribution characteristic, and the light of the LED 2 is collimated. Therefore, the phototransistor 3 and the slit 4 are moved with the voltage applied to the liquid crystal drive electrodes 5 and 6, and the light of the LED 2 is received by the phototransistor 3 through the slit 4.

FIG. 4 shows the relationship between the DC output obtained by integrating the received light by the condenser 12 and the moving distance of the phototransistor 3 and the slit 4. The horizontal axis in FIG. 4 indicates the moving distance (μm), and the vertical axis indicates the signal strength (mV). The total moving distance is equal to the width of the liquid crystal pixel. Since the signal intensity varies depending on the position of the phototransistor 3, it is possible to know a fine position by quantizing the signal intensity.
For example, if the resolution is taken up to 10 bits, the vertex of the intensity change graph of FIG. 4 indicates the 512th position in the middle of 10 bits. Thus, it is possible to determine the position after the 512th position and the position before the 512th position. This means that the resolution increases when the liquid crystal display panel 7 is used as a scale.

[0019]

According to the present invention, since the liquid crystal itself has a lens effect, the sharpness of the contour of the pixel is improved, and the quality of the photoelectric scanning signal can be improved in each step. . The entire configuration can be simplified by omitting the surrounding optical system by the lens built-in type.

Further, when the present invention is applied to a scale, a lens array is incorporated in the scale main body, and the configuration of the position reading unit can be simplified. Since the scale uses the lens effect of the liquid crystal, the transmission method and the reflection method can be manufactured on the same panel, so that it is not necessary to consider the deposition method of the memory material for each application as in the related art. By suppressing the diffraction (wraparound) of light that could not be eliminated by the conventional method, optical linearization of distance versus sensor signal was realized. This makes it possible to simplify the light source, peripheral optical components, detector configuration, and electric circuit of the scale unit as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a liquid crystal display reading device of the present invention.

FIG. 2 is a principle diagram of the present invention.

FIG. 3 is a diagram showing applied voltages to liquid crystal drive electrodes 5 and 6;

FIG. 4 is an explanatory diagram of a relationship between a light detection position and a signal intensity.

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[Procedure amendment]

[Submission date] September 18, 2000 (2009.1.
8)

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

FIG. 3

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

Claims (5)

[Claims] 1. A liquid crystal display panel comprising a plurality of pixels, a liquid crystal drive section for applying a voltage to the liquid crystal display panel to cause a lens function, a projector for irradiating the liquid crystal display panel with light, and an irradiation for the liquid crystal panel. A liquid crystal display panel reading device, comprising: a light receiver for receiving transmitted / scattered light of the transmitted light. 2. A liquid crystal display panel having a cell gap of 1 to 10
0 μm, the liquid crystal driving section is 10 to 10000 Hz, 3 to 1
2. The liquid crystal display panel reading device according to claim 1, wherein a rectangular wave of 8 V is applied. 3. A liquid crystal display panel 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 antiferroelectric liquid crystal, and a polymer. 2. The liquid crystal display panel reading device according to claim 1, wherein the device is a dispersion type liquid crystal. 4. The light emitting device according to claim 1, wherein the light emitting device is a light emitting diode, a laser, a lamp, or an EL (electroluminescence).
The liquid crystal display panel reader according to the above. 5. A light receiving device comprising: a photodiode, a photomultiplier,
2. The liquid crystal display panel reading device according to claim 1, wherein the device is a solid-state light receiving sensor, a pyroelectric sensor, or a thermopile.