JPS59224820A - Variable focal length lens - Google Patents

Abstract

PURPOSE:To vary the refractive index of a liquid-crystal lens cotinuously by applying an external electric field or magnetic field to a cyanobiphenyl liquid- crystal cell which is in the shape of a lens and has liquid-crystal molecules oriented in one direction, and controlling the orientation state of the liquid- crystal molecules. CONSTITUTION:When an AC voltage is applied to the liquid-crystal cell wherein field-effect liquid crystal with positive dielectric anisotropy is charged between two transparent electrode substrates and liquid-crystal molecules are oriented in parallel to the substrates, the liquid-crystal molecules change direction continuously at right angles to the substrates at an applied voltage higher than a threshold value, and the apparent refractive index of the liquid-crystal cell varies from a value for abnormal light to a value for normal light with incident light polarized in the orientation direction of the liquid-crystal molecules. For the purpose, the lens 3 is formed by using the field-effect liquid crystal which is oriented in parallel and has positive dielectic anisotropy, and liquid-crystal molecules are slanted with the applied voltage 5 to vary the apparent refractive index of the liquid-crystal cell, varying the focal length of the lens 3 continuously.

Description

[Detailed Description of the Invention] When the ability to adjust the focal length of the eyeballs deteriorates, such as with presbyopia, glasses with two different focal lengths for near and far distances may be used, or spectacle lenses may be used. It is inconvenient that the camera has regions with partially or continuously different focal lengths, and objects must be viewed through the regions each having an appropriate focal length at close or far distances.

In addition, when the crystalline lens is removed due to a disease such as "Sokohi", conventional glasses with fixed focal length lenses can
In daily life, it was necessary to prepare several types of lenses and use them depending on the situation. Therefore, in order to eliminate the inconvenience when using these eyeglass lenses, the present invention aims to construct a voltage-controlled variable focal length lens using a liquid crystal that operates at low voltage and low power consumption. .

In a material with uniaxial refractive index anisotropy, the refractive index for extraordinary rays and the refractive index for ordinary rays, which have a vibration direction in a plane including the optical axis, are different, so such a material is shaped like a convex lens or a concave lens, Figure 1 (abnormal ray) and Figure 2
As shown in the figure (ordinary ray), when switching between the extraordinary ray and the ordinary ray using the polarizing plate 1, the focal length of the lens 3 can be changed even though the shape of the lens 3 is the same, since the refractive index is different. I can do it. On the other hand, the liquid crystal molecules are oriented parallel to two transparent electrode substrates, and these substrates are arranged perpendicularly so that the liquid crystal molecules are twisted 90 degrees between the two substrates. T N (T w
istedNematiC＞Liquid crystal cells have the effect of twisting the polarization direction of input light by 90 degrees, but this TNN
When the voltage 4 applied to the liquid crystal cell exceeds a certain threshold, the liquid crystal molecules align in the direction of the electric field and lose their optical activity, and the input light passes through this liquid crystal cell without rotating its polarization direction. Therefore, as shown in FIG. 3, by aligning the vibration direction of the polarizing plate 1 with the optical axis direction of the material constituting the lens 3, and placing the O-N liquid crystal cell 2 between the polarizing plate 1 and the lens 3,
If the applied voltage 4 is lower than the threshold voltage, the input light is rotated by 90° in the vibration direction in the TN liquid crystal cell 2, and the input light becomes a lens with a refractive index relative to the ordinary ray.
When the voltage exceeds the threshold voltage, no rotation in the vibration direction occurs, and therefore the focal length of the lens can be switched by the voltage applied to the TN liquid crystal cell. However, with this method, the focal length of the lens cannot be continuously varied.

By the way, when a field-effect liquid crystal with positive dielectric anisotropy is placed between two transparent electrode substrates and an AC voltage is applied to the liquid crystal cell with the liquid crystal molecules oriented parallel to the substrates, the threshold value In response to the above applied voltage, the liquid crystal molecules continuously change their orientation perpendicular to the substrate, and the apparent refractive index of the liquid crystal cell changes as the incident light is polarized in the orientation direction of the liquid crystal molecules. It changes continuously from the value for extraordinary light to the value for ordinary light. It is known that this so-called field-controlled birefringence effect does not depend on the thickness of the liquid crystal cell and changes depending on the applied voltage rather than the applied electric field. In other words, the liquid crystal cell is shaped like a lens, and even if the thickness of the liquid crystal hill differs from place to place, optically uniform changes in refractive index can be obtained. Therefore,
The configuration shown in Fig. 4 is created using a field-effect liquid crystal with positive dielectric anisotropy with lenses 3 oriented in parallel, and an applied voltage 5 tilts the liquid crystal molecules (J causes apparent diffraction of the liquid crystal cell). By changing the ratio, the focal length of the lens 3 can be continuously changed.As a specific example, a liquid crystal lens with a radius of curvature of 121 mm was created using PCB, which is a cyanobiphenyl liquid crystal. Then, 10V
The focal length of the liquid crystal lens can be increased to 175mm by applying a voltage of
It can be changed from about 230n+m to about 230n+m. If a vertically aligned liquid crystal with negative dielectric anisotropy is used, the focal length will change inversely to the applied voltage, ie, from the value for ordinary light to the value for extraordinary light. Similar to applying a voltage, applying a [71 field can also change the alignment state of liquid crystal molecules, so a lens whose focal length can be varied by a magnetic field can also be obtained.

Furthermore, in the configuration shown in FIG. 5, the ordinary ray and the extraordinary ray are switched by the voltage 4 applied to the TN liquid crystal cell 2,
Furthermore, if the focal length is controlled by the voltage 5 applied to the liquid crystal lens 3, it is possible to obtain rough and fine changes in the focal length.

The present invention operates at a low voltage of about several volts and uses a liquid crystal cell with extremely low power consumption to construct a lens with a variable focal length of 5-variable, so it can be directly connected to an integrated circuit element, and is thin and lightweight. This allows it to be worn as a normal eyeglass lens. Furthermore, it can be applied to electronically adjusting the distance adjustment mechanism of optical equipment.

[Brief explanation of the drawing]

The drawings are for explaining embodiments of the present invention and their operational structure. Figures 1 and 2 show the basic principle of the variable focal length lens of the present invention, and Figure 1 shows the case of extraordinary rays. Fig. 3 shows a configuration example in which two focal lengths can be selected by combining TN liquid crystal cells and applying voltage, and Fig. 4 shows the case of the second town ordinary likelihood line. A voltage is applied to the lens to control the orientation of liquid crystal molecules, and the focal length can be varied by changing the induced birefringence. Figure 5 shows the configuration of a lens in which a TN liquid crystal cell is added to the configuration of Figure 4. In the figure, 1 is a polarizing plate, 2 is a TN liquid crystal cell, 3 is a 61I nons made of a material with refractive index anisotropy (liquid crystal), 4 is a TNGN high quality drive 14fff, and 5 is a liquid crystal Lens drive voltage by. 7- Figure 1 Figure 2

Claims (1)

[Claims] The refractive index of the liquid crystal lens is continuously changed by applying an external electric or magnetic field to a cyanobiphenyl liquid crystal cell that is shaped like a lens and has liquid crystal molecules aligned in one direction to control the alignment state of the liquid crystal molecules. A variable focal length lens.