JPS62298727A - Vibration analysis device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application 1 The present invention relates to a vibration analysis device for analyzing vibration of an object.

[Prior Art] Conventionally, vibration analysis devices for analyzing the vibrations of objects have been designed to emit light from a strobe light in synchronization with the vibration frequency of the object being measured, or by setting it to a minute difference. is used.

Using such a strobe light, it was possible to stop the motion of a rapidly vibrating object or view it as a series of photographs, making it easy to analyze the vibrations.

[Problems to be solved by the invention] However, strobe lights have limited brightness and can be used in dark rooms or at night; For analysis that requires measurements outdoors under sunlight or for analysis that requires measurements outdoors, there is a problem in that the light intensity of the strobe light is insufficient and cannot be used for analysis.

For this reason, there has been a desire for a vibration analysis device that can be used in large areas and under strong sunlight.

Means for Solving Problem E] The present invention has been made to solve this problem, and in a vibration analysis apparatus for analyzing the vibration of a vibrating object to be measured, a high-speed response liquid crystal display element is illuminated. The present invention provides a vibration analysis device characterized in that it is used as a shutter.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of the basic configuration of the present invention.

FIG. 1 shows an example of analyzing the vibration of a loudspeaker as an object to be measured, where l is a high-speed response liquid crystal display element, 2 is an oscillator for driving the high-speed response liquid crystal display element, and 3 is a frequency counter; 4 is the output waveform of the oscillator; 5 is a loudspeaker as an object to be measured; 16 is an illumination light source; and 7 is an observer.

In this case, a high-speed response liquid crystal display element is used whose shutter opens when the output of the oscillator is on, but it goes without saying that it can also be used in the opposite case.

The objects to be measured whose vibrations can be analyzed using the present invention include:
In addition to the above-mentioned loudspeakers, there are various musical instruments, cushioning materials, various structural materials, buildings, rotating bodies, etc., and their frequencies,
It can be used to analyze vibration modes, rotational speed of rotating bodies, surface wobbling, shaft wobbling, etc.

Since the present invention can also use sunlight as a light source for illumination,
It can also be used to analyze the vibrations of various buildings, suspension bridges, iron bridges, rails, towers, and large machines as large objects to be measured.

It can also be used to track objects moving in one direction.

Further, the observer may view the image directly with his or her mouth, or a camera may be directly attached to an optical shutter to take a photograph.

Although it has been proposed to use a liquid crystal display element as a shutter for a camera, it has not been practically used because a sufficient shutter speed cannot be obtained or the response speed is slow. In the present invention, since a high-speed response liquid crystal display element is used instead of a conventional slow-speed liquid crystal display element, such use is also possible.

In the present invention, since the high-speed response liquid crystal display element is configured to transmit light repeatedly at a certain constant period, it is preferable to use one having the following configuration.

That is, a pair of transparent substrates with transparent electrodes are arranged so that the transparent electrodes face each other, the periphery is sealed with a sealant, nematic liquid crystal is sealed inside, and a pair of polarized light is placed outside the nematic liquid crystal layer. Each transparent substrate is horizontally aligned, and both transparent substrates are arranged so that their horizontal alignment directions are almost perpendicular to each other, and the polarization axis of each polarizing film is aligned with the plane of each substrate. The liquid crystal molecules are arranged approximately parallel to or perpendicular to the alignment direction, and the relationship d/p between the pitch p of the nematic liquid crystal and the substrate gap d is 0.5X.
By sequentially turning on and off the voltage applied between both transparent electrodes, the liquid crystal molecules are The liquid crystal molecules take a twisted state of approximately 90° + 180' x n, and when the voltage is on, the liquid crystal molecules are vertically aligned, and when the voltage is off for a short time after the voltage is on, the liquid crystal molecules are relaxed to the twisted state when the voltage is off. Almost 90°+
1110'
This is a high-speed response liquid crystal display element that can change the light transmittance by using two states: a twisted state of °×m.

This high-speed response liquid crystal display element does not change the light transmittance by using only the two stable states of voltage on and off, which are used in ordinary liquid crystals, but completely changes the light transmittance by turning off the voltage for a long time. When the liquid crystal is turned off, it is in a more twisted state than normal liquid crystals, and there are two metastable states: a stable state when the voltage is on, and a relaxed state that is completely off when the voltage is turned off.
The metastable state does not last long, but it can be used in applications where the liquid crystal repeatedly turns on and off at short intervals of several meters to several seconds, as in the present invention. is suitable and provides high contrast with fast response.

FIG. 2 is a sectional view showing the basic structure of this high-speed response liquid crystal display element.

In Fig. 2, IIA and IIB are transparent substrates made of glass, plastic, etc., and their inner surfaces are coated with tin fermentation,
Transparent electrodes 12A, 12 such as indium oxide-tin oxide
B is formed by patterning into a desired pattern as necessary. The surface of this transparent electrode is horizontally aligned by rubbing or diagonal vapor deposition so that the liquid crystal molecules are horizontally aligned in one direction. The cell is sealed with a sealing material 13, and a nematic liquid crystal 14 is sealed inside to form a liquid crystal cell. A pair of polarizing films 15A and 15B are arranged on the outer surface of this liquid crystal cell so that the polarization axis of each polarizing film is substantially parallel to or substantially perpendicular to the orientation direction of liquid crystal molecules on each substrate surface. The polarizing films are arranged so that their polarization axes are substantially parallel or orthogonal to each other.

In addition to this, applications such as those used in general liquid crystal display devices, such as forming metal leads on transparent electrodes, etc.
Except for the parts that change the light transmittance, an opaque mask is formed by electroless Ni plating, Or vapor deposition, etc., a color filter is formed, and polyimide, polyamide,
An overcoat for alignment films such as silica or alumina is formed on transparent electrodes, and spacers such as glass fibers, alumina particles, plastic particles, etc. are sprinkled or used to maintain an accurate gap between the substrates within the liquid crystal cell. You may also apply a sealant.

The alignment directions of this high-speed response liquid crystal display element may be perpendicular to both substrates, and the polarization axes of the polarizing films may be arranged parallel or perpendicular to the respective alignment directions.

For example, if the polarization axes of both polarizing films are arranged in parallel, light will pass through when on, and no light will pass through when off.

In this high-speed response liquid crystal display element, like a normal liquid crystal display device, the liquid crystal molecules are approximately 90' + 180 when the voltage is off.
' Take the first stable state, which is the twisted state of X n,
When the voltage is turned on, the second stable state, which is a vertically aligned state, is taken, and up to this point it is the same as a conventional liquid crystal display device.

However, in this high-speed response liquid crystal display element, since the twist angle of the liquid crystal molecules is large, in addition to these two stable states, when the voltage is turned off after the vertical alignment state, which is the second stable state 7u- when the voltage is on. , the relaxation state to the twisted state which is the first stable state when the voltage is completely turned off, although for a short time, is approximately 90' + 180' Xm (m is O≦m<n(
7) It has at least one metastable state which is a twisted state of (indicates an integer). This metastable state occurs extremely quickly from the vertically aligned state, which is the second stable state, because the twisting force of the liquid crystal itself is strong.
The state is reached at a high speed of approximately ec, is maintained for a certain period of time, and reaches either the next metastable state or the first stable state. This high-speed response liquid crystal display element can be driven between two states, the second stable state when the voltage is on, and at least one metastable state, and can be turned on and off at extremely high speed.

Since this metastable state is not stable for a long time, it sequentially shifts to the next metastable state or the first stable state, but each of these is determined by the orientation direction, so the twist is 180° between them. This will result in an increase. For this reason,
The change in light transmittance between the metastable states and between the metastable state and the first stable state is relatively small. In particular, the change between the metastable states of 906° and 270° is so small that it is hardly recognized that the state has changed.

In this case, the relationship between the pitch p of the nematic liquid crystal and the substrate gap d is 0.5X n < d/P < 0.5+0
．． It may be 5×n (n is an integer of 1 or more).

As a result, when the horizontal alignment directions of both substrates are perpendicular, the liquid crystal molecules are aligned at 90° + 180° when the voltage is off.
Take the twisted state of ×n. This is the first stable state.

When a voltage is applied, the liquid crystal molecules stand up, become almost vertical, and are oriented vertically. This is the second stable state.

When the voltage is then turned off, the liquid crystal molecules tend to become twisted and align in the orientation direction of the substrate. In this case, in this high-speed response liquid crystal display element, the liquid crystal molecules are in the first stable state at 90''+tao° when the voltage is completely turned off.
×n twisted state, i.e. 270', 450°, 63
Since the liquid crystal molecules are twisted greatly at 0°, ..., etc., even when the voltage is turned off, the liquid crystal molecules do not immediately return to this state, but first become 90'', then 270°, and so on.
450', etc., the torsion gradually expands, and a metastable state is reached.

In addition, in this case, the alignment state of liquid crystal molecules is approximately 90°+
The twisted state of 180"Xm (m is an integer of O≦m<n) is made to match the pretilt angle obtained by the horizontal alignment process, that is, the helical pitch of the liquid crystal molecules is the same at either end of the molecule. This particular metastable state tends to last much longer than other metastable states, sometimes lasting more than a few seconds. It is preferable to take this into account and determine the direction of the alignment process. In particular, alignment in a metastable state with less 180° twist than the first stable state is preferred because this metastable state can be easily stabilized.

For this purpose, for example, when using a left-handed helical liquid crystal with a 450° twist, in FIG. 11B, the rubbing direction may be changed from the lower right to the left -1-.

In this way, we adjust the liquid crystal so that the first stable state is 450°, i.e. we use a liquid crystal with 1 < d / p < 1.5, the metastable state is 270°, and this 270°
Preferably, the alignment condition is at .degree.

This is because the larger the d/p of the liquid crystal and the stronger the twisting force of the liquid crystal molecules, the faster the first metastable state at 90° will be reached, and the first stable state will be at 270°.
This is because a faster response is possible in the case of 450° than in the case of .

The difference between the first stable state being 270° and 450° is larger than the difference between 450° and 830°. This means that the first stable state is 270°
This is because the metastable state of the device is only 80 degrees, and it is considerably faster than the conventional liquid crystal display element whose first stable state is 906 degrees, but the one whose first stable state is 450 degrees is faster. It will be even faster. In addition, this high-speed response liquid crystal display element turns on and off between two states: a second stable state when the voltage is turned on and a metastable state immediately after the voltage is turned off, and the longer the metastable state is, the more likely it is that it can be used. It is preferable that the angle is large and the first stable state is 450°. In particular, by setting the first stable state to 450° and setting the metastable state of 2706 to a matching state where the orientation of the liquid crystal molecules and the pretilt match, it becomes possible to repeat switching even for a few seconds.

Although the response speed for transition to a metastable state tends to improve as the torsion angle increases, setting a torsion angle of 8306 or more means that the first stable state is 270° and 450°.
It is most preferable to set the angle to 450 degrees because the difference from the case of 450 degrees is not very large, and on the contrary, the driving voltage increases, circular polarization increases, light transmittance decreases, and contrast decreases. Furthermore, when the twist angle is increased, the retardation color tends to become stronger, which may result in an undesirable color.

[Function] In this high-speed response liquid crystal display element, the light beam emitted from the illumination light source is incident on the object to be measured, and a portion of the reflected light beam is directed toward the high-speed response liquid crystal display element.

The transmitter allows the incident light beam to selectively reach the viewer when the shutter of the fast-response liquid crystal display element is opened.

According to this principle, when the vibration frequency of the object to be measured and the shutter frequency of the high-speed response liquid crystal display element are synchronized, the object to be measured appears to be stationary.

In this case, the synchronized frequency can be determined by a frequency counter, and thereby the vibration frequency of the object to be measured can be determined.

Furthermore, by preventing these from being completely synchronized so that the frequencies are slightly shifted, it is possible to observe the object to be measured as if it were vibrating at the difference in frequency.

[Example] Example 1 A vibration analysis device for analyzing the vibration of a loudspeaker as shown in FIG. 1 was created. This high-speed response liquid crystal display element was manufactured as follows.

A glass substrate with a transparent electrode on which a polyimide alignment film is formed is rubbed, and the two substrates are placed with their electrode surfaces facing each other so that the rubbing directions are perpendicular and aligned at 270@, and the surrounding area is was sealed with a sealant except for the injection port, and liquid crystal was injected through the injection port to form a cell. The cell gap of this cell is 4. It was BJLm.

This liquid crystal is a Merck liquid crystal r ZLT-15B5J with a refractive index anisotropy Δn of 0.13, to which 5.5 wt% of cholesteryl nonanate is added as a chiral component so that the helical pitch is 3.77 zm. It was used.

A pair of polarizing films was placed on the front and back sides of this cell so that their polarization axes were parallel to each other.

In the high-speed response liquid crystal display element manufactured in this way, the liquid crystal molecules were in a state twisted by 450° when no voltage was applied, and the device was in the first stable state. In this state, light travels within the liquid crystal cell along the twist of the liquid crystal molecules,
The light is twisted by 450 degrees, and the light incident on the liquid crystal optical switch device is not transmitted because the polarization axes of the pair of polarizing films are parallel.

Next, a pulsed voltage is applied at a certain frequency. While this voltage is applied, the liquid crystal molecules become vertically aligned,
A second stable state has been reached.

In this state, the liquid crystal cell is equally good and bad for light, and the light that entered the liquid crystal optical switch device was transmitted because the polarization axes of the pair of polarizing films were parallel.

Next, when the voltage is turned off, the liquid crystal molecules within the cell instantly enter the first metastable state twisted by 80°, and the incident light that passes through the front polarizing film travels inside the cell according to the twisted structure of the liquid crystal, and its polarized light component is It was twisted by 90° and could no longer pass through the back polarizing film, and light was blocked.

Since this first metastable state is a mismatched state and is not very stable, the twisting of the liquid crystal molecules progresses further in a relatively short period of time, resulting in a second metastable state with a 270° twisted structure. Even in this state, incident light was blocked as in the 90° twisted structure, and the contrast change due to this change was slight. This 2706 twisted structure is relatively stable because the alignment state of the liquid crystal molecules matches the pretilt angle due to the horizontal alignment process, and is in a consistent state.
When the driving frequency was lowered, it continued for several seconds at room temperature. Note that when the device was used for a longer period of time, the structure shifted to a 450° twist structure.

In this example, in order to observe the vibration of the loudspeaker, we do not use slow pulses lasting several seconds, but instead apply pulses several hundred times per second. It turned on and off between the tilted orientation and the first stable state of vertical orientation, enabling high-speed and high-contrast switching, and the vibrations of the loudspeaker could be clearly distinguished.

Example 2 The rotation of a turbine used under sunlight was observed using the same vibration analysis device as in Example 1.

Even when used under sunlight, the rotation status can be determined because it uses a high-speed response liquid crystal display element, and if it is synchronized with the rotation, it will appear to have stopped, and if it is slightly out of synchronization, it will slow down. It looked like it was rotating.

[Effects of the Invention] Since the vibration analysis device of the present invention uses a high-speed response liquid crystal display element, it can be used to analyze vibrations under sunlight, vibrations of light-emitting objects, etc., which could not be used with conventional strobe lights. It becomes possible to analyze vibrations of large objects.

Furthermore, since a high-speed response liquid crystal display element is used, the power consumption is small even when the device is turned on and off at high speed, and it can be driven by batteries, which has the advantage that the device itself can be made inexpensive and compact.

The vibration analysis device of the present invention can be applied in various ways without detracting from the effects of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of a vibration analysis device of the present invention. FIG. 2 is a cross-sectional view of an example of a high-speed response liquid crystal display element used in the vibration analysis device of the present invention.

Claims (4)

[Claims] (1) A vibration analysis device for analyzing vibrations of a vibrating object to be measured, characterized in that a high-speed response liquid crystal display element is used as an optical shutter. (2) In a high-speed response liquid crystal display element, the relationship d/p between the pitch p of the nematic liquid crystal and the substrate gap d is larger than 0.5×n and smaller than 0.5+0.5×n (n is 1 or more). By sequentially turning on and off the voltage applied between both transparent electrodes, when the voltage is off, the liquid crystal molecules are twisted at approximately 90° + 180° x n, and when the voltage is on, the liquid crystal molecules are vertically aligned. When the voltage is turned off for a short time after the voltage is turned on, the liquid crystal molecules are in a relaxed state to the twisted state when the voltage is turned off. It is possible to change the light transmittance by using two states: the vertically aligned state of liquid crystal molecules when the voltage is on, and the twisted state of approximately 90° + 180° x m when the voltage is off. The vibration analysis device according to claim 1. (3) The vibration analysis device according to claim 2, wherein the alignment processing directions of the high-speed response liquid crystal display element are aligned in a metastable state with less twist by 180° than in a stable state when the voltage is turned off. . (4) The vibration analysis device according to claim 3, wherein the high-speed response liquid crystal display element is twisted at 450° and matched in a metastable state with a twist of 270°.