KR920008979Y1 - Exposing control apparatus using twisted neumatic liquid crystal plate - Google Patents

Abstract

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Description

Exposure control device using twisted pneumatic liquid crystal panel

1 is a plan view of the present invention.

2 is a view of the tilt angle and rotation angle change coordinates for the liquid crystal molecules of the present invention.

3 is Tilt and rotation angle coordinate plots calculated as a function.

* Explanation of symbols for main parts of the drawings

1: twisted pneumatic liquid crystal 2: dielectric thin film

3: polarizer 4: analyzer

5: antireflective coating layer

The present invention relates to an exposure control device that controls the amount of light in a light application device for a certain period of time. In particular, a twisted Neumatic Liquid Crystal plate is placed at the center and the polarizer and the analyzer are integrated at both sides to be used for a camera. Exposure control device.

Conventional exposure control device is a mechanical device that controls the rotation speed and the area of the chopper by using a chopper, and transmits by using a resonance condition by a piezoelectric transducer and an RF signal. Acousto-optic control devices are known that control the amount of light being emitted. The device using the chopper method is not easy to control the precise rotation speed of the chopper by rotating the chopper, and the area control by adjusting the area of the chopper also has limitations in modern optical applications that require precision and difficult to control the exposure. Was. In addition, the acoustic and optical control using the piezoelectric transducer and the high frequency signal must also generate a high frequency, thereby causing a cost increase and it is difficult to maintain a constant frequency according to the change of the surrounding environment.

The present invention grows the twisted pneumatic liquid crystal between the polarizer and the analyzer without using the opening and closing mechanism parts for light control, and applies the voltage to the grown liquid crystal to change the arrangement of the liquid crystal molecules so that light is transmitted. Therefore, since the arrangement is changed by the amount of energy received by the liquid crystal molecules by the applied voltage, an object of the present invention is to control the exposure time according to the magnitude of the electrical signal.

For this purpose, the present invention can be achieved by growing a twisted pneumatic liquid crystal, forming a dielectric thin film on both sides of the liquid crystal, integrating a polarizer and an analyzer into the dielectric thin film, and providing a voltage to the dielectric thin film. . In this case, the polarizer and the analyzer outside form an antireflective coating window.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The twisted pneumatic liquid crystal 1 in which the liquid crystal is grown in a twisted state, the dielectric thin film 2 integrated on both sides of the twisted pneumatic liquid crystal 1, and both sides of the dielectric thin film 2 so as to pass light in the mutually perpendicular direction It consists of a polarizer 3 and an analyzer 4 fixed to it. The outside of each polarizer 3 and the analyzer 4 is coated with an antireflective coating window 5, and a voltage V at which the current is controlled by the variable resistor Rv is provided at the ends of both dielectric thin films 2. The dielectric thin film 2 uses tin dioxide (SnO ₂ ).

In using the present invention configured as described above, when the exposure operation button (not shown) is pressed, the voltage to be applied to the present invention by the light amount detecting device (not shown) which detects the intensity of the light quantity entering the exposure control device of the present invention. The amount is determined. Accordingly, when the applied voltage V is applied for a predetermined time, the arrangement of the liquid crystal molecules of the twisted pneumatic liquid crystal 1 is changed, so that the polarization direction of the light passing through the polarizer 3 can be changed to transmit the light. Will be.

At this time, the polarizer 3 and the analyzer 4 are fixed to a material such as a film or glass that transmits in one direction to be orthogonal to both sides of the liquid crystal 1.

In more detail, the light incident on the polarizer 3 is absorbed by the vertical polarizer 3 (e.g., a horizontal component) and passes only the vertical component. At this time, when the voltage V is not applied to the liquid crystal molecules of the liquid crystal 1 through the dielectric film 2, the vertical component passed by the vertical polarizer 3 passes through the liquid crystal 1 as it is, and the analyzer Since 4 serves as a horizontal polarizer, the vertical component is absorbed, so that light cannot pass through the analyzer 4. This is because the analyzer 4 and the polarizer 3 are installed in the same material or perpendicular to each other. If the voltage V is applied to the dielectric thin film 2 and the voltage is applied to the liquid crystal molecules of the liquid crystal 1, the arrangement of the liquid crystal molecules is changed because the liquid crystal molecules absorb energy applied by the electric field, and thus the polarizer Since the polarization state of the light passing through is changed, the light is transmitted through the analyzer 4. In this case, the antireflective coating layer 5 is formed outside the polarizer 3 and the analyzer 4 to protect the polarizer 3 and the analyzer 4 as well as to improve light transmittance. A phenomenon in which an arrangement is changed by applying an electric field to the liquid crystal molecules of the twisted pneumatic liquid crystal 1 will be described through a formula.

First, since the optical properties of the liquid crystal molecules are influenced by the long axis alignment direction, a coordinate system as shown in FIG. 2 is used to explain the change in the long axis alignment direction. The long axis unit vector n of the liquid crystal molecules may be represented by angles α and β, where α is an angle between n and the xy plane, and β is an angle between the x-axis and the line projected on the xy plane. The free energy of the liquid crystal is divided into elastic energy and free energy by the applied electric field, and the liquid crystal molecules are arranged while satisfying the conditions for minimizing the free energy of the system. In addition, the total energy density ft is represented by the sum of fk and fε.

fk: elastic energy density

fε: Energy density when electric field is applied in Z direction

f (α): k ₁ Cos ² α + k ₃ Sin ² α

g (α) = Cos ² α (k ₂ Cos ² α + k ₃ Sin ² α)

k ₁ , k ₂ , and k ₃ are the modulus of elasticity of the spray, twist and bend of the liquid crystal

The liquid crystal system applies the Euler-Lagrangian equation using a condition that minimizes ft.

Based on the formulas [2] and [3], for example, the Z-axis is used when using boundary conditions with α = 5 ° when n = 0, β = 0 °, and α = 5 ° and n = 90 ° when n = 1. As shown in FIG. 3, the angles of inclination angle α and rotation angle β vary according to the change of the applied voltage V, and thus the arrangement of liquid crystal molecules changes accordingly. In FIG. 3, the applied voltage V is compared with the reference voltage Vc to change the arrangement, and the reference voltage Vc may vary according to the design of the liquid crystal 1.

As described above, the present invention can control exposure by controlling the transmission of light by changing the polarization state of incident light in the direction of the long axis of the liquid crystal molecules according to the change in the voltage applied by placing the liquid crystal between the polarizer and the analyzer. It is a convenient device that can control the exposure by simply changing the voltage without the need for a separate control element such as high frequency energy.

Claims (4)

It consists of a twisted pneumatic liquid crystal (1), a dielectric thin film (2) integrally formed on both sides of the liquid crystal (1), and a polarizer (3) and an analyzer (4) fixed to both sides of the dielectric thin film (2), respectively. , Exposure control device using a twisted pneumatic liquid crystal, characterized in that to adjust the light transmittance by varying the voltage (V) to the dielectric thin film (2). The exposure control apparatus using twisted pneumatic liquid crystal according to claim 1, wherein the dielectric thin film (2) is tin-dioxide (SnO ₂ ). The exposure control apparatus using twisted pneumatic liquid crystal according to claim 1, wherein an antireflective coating layer (5) is formed on outer surfaces of the polarizer (3) and the analyzer (4). The exposure control apparatus using twisted pneumatic liquid crystal according to claim 1, wherein the polarizer (3) and the analyzer (4) are configured to absorb or transmit mutually orthogonal components.